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2AIMEN,Asociaci��n de Investigaci��n Metal��rgica del Noroeste, C/Relva Porriño-Pontevedra (Spain).

 

4th INTERNATIONAL CONFERENCE ON NDT

Hellenic Society for NDT 
11-14 October 2007, Chania, Crete-Greece

 

 

PREFACE

 

The papers contained in this volume constitute the proceedings of the 4rh International Conference on Non Destructive Testing held at the building of "Megalo Arsenali", the Center of Mediterranean Architecture (CAM), a historical and wonderful Venetian building located in the old port of Chania, Greece, October 11-14, 2007. The conference was organized by the Hellenic Society of Non Destructive Testing and it constitutes the 9th, as five National and three International NDT Conferences have been taken place before this one by the same Society.

    The theme of the conference, " Non Destructive Testing: Skills- Applications- Innovations, Industrial Manufacturing- Aerospace- Marine" was chosen in order to emphasize and promote the NDT methods to a wide range of industrial and scientific areas.

    The aim of the Conference is to bring together scientists and engineers, in the attempt to exchange recent experiences in the research and development activities, in the field of NDT.

    The technical programme with 112 oral and poster presentations, 62 from abroad and 50 from Greece has been organized in sessions related to industrial as well as to scientific areas. The Book of Abstracts and the Proceedings were set out also accordingly in a CD.

    In the present Conference more than 350 authors, attendee, exhibitors and sponsors coming from 30 different countries have been applied for participation.

    The President of the Hellenic Society of NDT, Professor Ioannis N. Prassianakis, who will emphasize the importance of NDT for the human life from the far antiquity up to nowadays, will open the conference.

    Dr. Sotirios J. Vahaviolos, past president of ASNT, will give the opening lecture with the title: ��NDT-the science, the business and the future forecasts��.

    Sincere thanks go to all participants and exhibitors especially to those from abroad, for coming to Chania and hope that they will enjoy the conference. Many thanks should be given to all sponsors of the Conference for their financial support. Also, special thanks to Professor G. C. Papanicolaou from the University of Patras, Dr. K. Giannadakis, E. Prasianaki and G. Petridis who had the secretarial responsibility of this conference.

    Finally, I would like to thank the Organizing and Scientific Committees members, for organizing the sessions and achieving a close connection between industry and R&D and also for their excellent work. Sincere thanks to all authors and presenters for their contribution as well as to numerous other individuals who contributed to the success of this conference. 
 

 

Chania, Crete-Greece, October 2007

 

    The Chairman of Conference

    Professor Ioannis N. Prassianakis

                                                                                      President of HSNT 
 
 
 
 
 
 
 

 

OPENING CEREMONY  

    NDT means economy and safety in a contemporary society

 

by 

I. N. Prassianakis 

President of HSNT, Professor at the National Technical University of Athens (NTUA), Faculty of Applied Mathematics and Physics Sciences, Department of Mechanics, Laboratory of Strength and Materials, Iroon Polytechniou 5, Gr-157 73, Zografou Athens,

E-mail: prasian@central.ntua.gr 

ABSTRACT 

    One of the more important possibilities of nowadays is the use of materials with properties that never up to today had been put in the service of the man. From the Caverns or the Stone Residences and the simple machines the "Wise Man" creates of many multi-storied skyscrapers, airplanes, boats, trains and robots. 

    All these marvels of modern technology are manufactured from materials, which should be selected carefully and have the desirable properties. But also the manufactured objects and constructions from these materials should be checked, as the properties of the materials do not remain constants.  

    The properties of materials and constructions can be measured mainly by two basic ways: The Destructive and the Non Destructive Testing Methods.

    The Non Destructive Testing ensures fast, reliable, economic and safe testing, particularly in the case of high danger constructions. 

    The historical and scientific truth, is that the Non Destructive Testing was applied for testing materials and constructions, before the appearance of Destructive Testing and also that this way of materials testing was known and was applied by the people, in the far antiquity, thousands years ago, around the world.  From archeological Greek findings, e.g., we can see that the ancient Greeks carried out the quality control of every material and goods, using absolutely nondestructive methods. 

    So, based in historical and scientific information, that the archaeological and scientific research have brought in the light, we are led to the conclusion that the ancient Greeks knew and also applied the Non Destructive Testing for the qualitative control of the materials that they used. This way of testing must would be applied, then by subjective way, that is to say with the help of the five human senses (sight, hearing, touch, smell and taste) with which the mother nature has dowered us. 

    The Non Destructive Testing is a modern tool that provides the possibility for better quality of life, in a safe and healthy environment with better, more safe and durable and more economic constructions.

 

 

    NONDESTRUCTIVE TESTING (NDT):

    THE SCIENCE, THE BUSINESS AND FUTURE FORECASTS

 

Dr. Sotirios J. Vahaviolos 

MISTRAS Group Inc., Chairman & CEO

Honorary Member of ICNDT

Past President of ASNT (USA)  

ABSTRACT 

The recent collapse of the I-35 Bridge in Minnesota, USA, brings infrastructure safety, integrity and performance to the ��front page�� of every news information channel around the globe. Local and federal governmental organizations increasingly focus on regulating maintenance and NDT inspection of industrial and public infrastructure (including bridges, refineries, nuclear and fossil fuel plants, pipelines, etc.). The continued utilization of the aging infrastructure and the increased focus of management for productivity and profitability has lead to ��lean�� construction and manufacturing, extension of useful life of assets and minimum downtime through Predictive Maintenance and NDT.  In addition, the need for increasing governmental regulatory compliance and stringent environmental penalties has led to customer demands for advanced low cost automated digital NDT solutions that can guarantee overall Plan Asset Integrity Management.  In the United States, most bridges are 30-35 years old.  We had approximately 500 bridge failures in the last decade. Aging plant/manufacturing process industry facilities have resulted in over $50 billion spent in managing corrosion. Less than 5% increase in refinery capacity allowed environmentally in the last 25 years has led to consistent plants over-utilization.  Over 60% of the U.S. pipelines are more than 45 years old, while most of the nuclear power plants are beyond their original designed life and now require constant monitoring of several critical components. 

To address all of the above issues, we need a worldwide revival of NDT research!  In the United States especially, such research in the past was heavily supported by military needs for quality and material safety.  Now that such activities are not a top government priority industry must bear more of the research expense load.  Organizations such as the Electric Power Research Institute (EPRI) financed by private U.S. power industry has lead joint research with several universities and companies like ours to develop UT Phased Array (PA) technology capable of replacing Radiography for thick wall boilers in both the fossil and nuclear power plants.  Such projects result in excellent scientific achievements in 3D UT imaging and easy visualization of thick wall weld defects, while helping users increase their workers productivity at staged plant shutdowns by eliminating downtime due to the radiographic worker barriers restrictions.  The most recent environmental accidents are driving hard the need for ��more sophisticated�� NDT inspections where visual must be replaced with such technologies as Infrared, Automated UT, AE, Ground Penetrating Radar and vibration. The author will address   on-line remote monitoring and how is now coming to the front of NDT inspection arena. We will discuss advantages of such a new innovative technology while showing examples of pioneering installations/applications worldwide.  The paper will present the case that while NDT Inspectors find a mechanical integrity flaw indication and engineers perform a Fitness for Service (FFS) analysis that proves the existence and severity of a defect in the plant, operations personnel might not be able to do an instant shutdown for repairs or replacement of a plant component since it might be critical to the overall running of a plant.  In that case, today��s NDT technologies offer on-line, wireless remote monitoring using Acoustic Emission combined with other process parameters sensors (such detection methodology is based on ��sensor fusion��) for determining if the component conditions previously detected are worsening or what specific parameters are driving the existing defect to failure.  Such blend of NDT technologies and process sensors will satisfy the need of API (American Petroleum Institute) for Enhanced Process Safety. Innovations in this area by researchers will be rewarded with ample PERF research contracts that are typically given to professors and scientists of various industrial NDT concerns by API.  Over the past 20 years, our scientists have developed remote, on-line asset integrity monitoring strategies for comprehensive structural monitoring that combines local sensing and decision making capability with wireless remote coordinating systems that perform storage, display and analysis functions while providing alerts, performance assessments and recommended actions. In addition to the above the classical new materials NDT research will continue, but with emphasis on automated imaging technologies and rapid global defect identification. Research institutions with advances in MEMS technologies and low cost NDT permanent solutions will lead in the infrastructure applications.

The NDT business is rapidly transforming and is been incorporated within the more expansive term of Mechanical Integrity (MI). The user and owner of a plant within the MI umbrella is looking for comprehensive services that include engineering services, NDT inspection, NDT data archiving and management as well as overall plant integrity assessment and maintenance. The author will show examples of the new NDT needs for storing GBytes of files from Computer Radiography, automated UT, Phased Array, Guided UT waves etc. and all of that from a technicians day work. The use of wide use of ��Plant Condition Management�� and Risk Based Inspection (RBI) software will be discussed. Such information technologies are dominating today��s MI business and will be the standards for helping industry prove environmental government compliance.

The author will end his talk by presenting the concerns of ICND members for today��s wide shortage of NDT Certified professionals. Industry slides will be presented that show USA NDT personnel shortages of 5,000 by year 2010. Such numbers exclude the present USA nuclear industry that the EPRI/TVA report estimates >1,000 by year 2010. Considering the more than 40-nuclear plants constructed worldwide and with the start of the nuclear plants in USA by the end of 2008 industry expects the NDT personnel  shortages to be in excess of 15-20,000 NDT certified technicians. The need for internet based NDT training is now a must and some suggestions will be made. The author will conclude with a summary of the state of the NDT industry as a profession as he sees it today.

 

 

    THE ROLE OF NDT IN CONSTRUCTING SIZEABLE INFRASTRUCTURES:

    THE EXAMPLE OF OADYK

 

Em. Spanoudakis 

General Manager of OADYK, Chania-Greece 

 

    Non Destructive Measurement and Rapid Prototyping

    in the service of Cultural Heritage

 

Dr. Angeliki Kottaridi1, Dr. Sc. Techn2, Mr. Christos Gr. Drettas3 

1Curator of the Museum of Royal Tombs of Aiges

2ETH Horst A.  Beyer, President, Imetric GmbH

3M.Sc, AKMON Laboratories 

ABSTRACT 

Keywords:         Close Range Photogrammetry, Optical Scanning, Structured Light, Rapid Prototyping,  Surface Reconstruction, Cultural Heritage Documentation,  Archaeology, Sculpture,  Virtual Museum. 

In recent years we have witnessed the introduction of non contact measurement and testing technologies in the domain of the arts and archaeology. This application of Industrial Reverse Engineering techniques outside the Industrial fields has been further consolidated by the emergence of faster and less invasive techniques for the representation of complex free-form surfaces, typical of art sculptures and ancient findings, that where otherwise impossible to represent and reproduce because of the precious nature of the object itself, fragility, form complexity or at the best case extremely expensive in terms of time and monetary funds.

In this presentation the authors explain how Close Range Photogrammetry and Structured light 3D scanning technologies where applied for the reconstruction of the surface of ivory artifacts of very small size from the Museum of the Royal Tombs of Aiges (Vergina, Macedonia) .  Moreover, in this presentation the authors demonstrate the integration of rapid prototyping technologies that allowed the materialization of the acquired 3d data. This integration resulted  in faithful reproductions of the artifacts, directly from the digital model.

Furthermore, a qualitative and dimensional evaluation of both the process and materialized replicas has been performed and the initial findings indicate that the results of the application of Non Contact Testing and Measurement Technologies in the fields of art and archaeology are not only feasible but also present great benefits to the Cultural Heritage community. 

This paper demonstrates how Non Contact Testing and Measurement Technologies combined with Rapid Prototyping Technologies can be applied in the Field of Archaeology by proposing and presenting new, feasible and functional ways of recording, cataloguing, conserving, restoring, reproducing and presenting archaeological artifacts, monuments and sites. 

 

 
 
 
 
 
 
 
 
 
 
 
 
 
 

 

SESSION 1

ULTRASOUNDS-COMPOSITE MATERIALS  

    Visualisation of Guided Wave Propagation by Ultrasonic Imaging Methods

 

Dr.-Ing. Wolfgang Hillger 

DLR German Aerospace Center, Institute of Composite Structures and Adaptive Systems 
Lilienthalplatz 7, 38108 Braunschweig, Germany 
Telephone +49 531 295-2306, E-mail mailto:Wolfgang.Hillger@dlr.de 
Telefax +49 531 295-2399,  Internet http://www.DLR.de 

ABSTRACT 

Composite materials are more and more used for primary structures in aerospace components. Examples are the new aeroplanes Boeing 787 and the Airbus A350 which are mostly produced out of composites.

In order to take advantage of the specific properties of composites the complexity of the structures increases more and more. On the other hand the coasts for inspection after fabrication and especially in service have to decrease. Coast effective NDT-methods have to be implemented.

This paper presents the possibilities of guided waves inspection techniques for complex composite components. Guided waves such as Lamb waves can be easily excitated and received by applied piezo-elements and penetrate large areas so that complex structures in principle can be inspected (SHM). However, for each frequency in minimum two different wave modes exist so that the responses are difficult to evaluate. The Lamb wave research is carried out within the EU project AISHA. The ultrasonic imaging technique is successfully used for the visualisation of the Lamb wave propagation. This combination between SHM and ultrasonic technique provides the optimisation of the sensor and actuator placement and also an interesting method for in-field inspection of air aerospace components. The coupling of the scanning receiver transducer can be carried out with water split coupling as well as with air (non contact).    
 
 

 

    Propagation of ultrasonic Lamb waves in adhesively bonded lap joints

 

M.J. Santos, J. Perdigão 

Institute of Science and Materials Engineering, Dept. of Electrical and Computers Engineering, University of Coimbra, Portugal 

Abstract 

Adhesive bonding has been used lately with great success in several types of fabrication processes. The main advantages of this technique results from the favourable stress distribution, the smother appearance and the light weight of the final assembly when compared with other traditional bolting, riveting or spot welding techniques.Bonding gives also the possibility to join different materials in complex shape structures.

Due to manufacturing conditions or degradation during service, different bonding parameters need to be inspected. In industries where automated assembly methods may be used it is important that the dimensions of adhered joints, such as adhesive layer thickness and overlap length, are within tolerance and are measurable. The detection of defects such as voids in the adhesive or local separation of adhesive from one of the adherents is another need in all industries. The conventional point by point techniques rely mainly on the use of normal incidence scanning which is performed over the area containing the overlap region. This technique is time consuming and access to the joint area is needed. The use of ultrasonic Lamb waves is potentially a very attractive solution when large structural tests are demanded since they can be excited at one point and propagated over considerable distances.

This paper considers the bonded joint as a multilayer structure that is analysed using the Transfer Matrix method. In this particular case three layers (two adherents and the adhesive) are considered. The study of this propagation problem may be developed from matrix formulations which describe elastic waves in layered media. This technique combines the theory of the dynamics of the continuum within each layer with the conditions for the interaction at the interfaces between layers.

The behaviour of the different modes which propagates in the overlap region is obtained and is found that the relative amplitudes can be estimated based on the properties of the incident wave mode. It was verified that the excitation of these modes is governed by the degree to which their mode shapes match the mode shapes of the incident wave. This allows us to explain the physical phenomena that are behind the mode conversion, which could be used to a correct selection of modes for non-destructive evaluation of the bond region.

Other interesting result obtained was the possibility to determinate the attenuation of both longitudinal and transversal waves in plates using this model, that usually could be a difficult task using conventional pulse-echo technique, specially in thin plates. Using an emersion pitch and catch setup, the total attenuation, that is composed by the losses due to the leaking in the fluid and material damping can easily be obtained doing two measurements at different distances. The leaking losses can be obtained by knowing the bulk properties of both fluid and plate. So, attenuation of longitudinal and transversal waves (material damping) can be evaluated. In the experimental work two sets of lap joints built from 1mm and 4 mm thickness aluminium plates are tested using the fundamental S0 mode as incident wave. Very good agreement is found when compared with the theoretical predictions. 

 

    Ultrasound interferometry for the evaluation of thickness and adhesion of thin layers

 

J.B. Santos, M.J. Santos 

Institute of Science and Materials Engineering, Dept. of Electrical and Computers Engineering, University of Coimbra, Portugal 

Abstract 

This work deals with the evaluation of thin layers by a technique we called ultrasound interferometry, which is based on the resonance and antiresonance of ultrasound waves verified in the presence of some interfaces having different acoustical impedances. That is easily proved changing the frequency of a probe transmitting into a medium with parallel faces. Frequency values corresponding to two consecutive resonances and two consecutive antiresonances are directly correlated with the layer thickness and with the propagation wave velocity.

The proposed goal required first the development of equations relating to the multiple internal reflections and transmissions of waves against frequency.

In order to simulate this technique for an effective calculation of the thicknesses of very thin layers, some tests were accomplished considering three propagation media: coupling, layer and substrate. The results illustrate essentially painting layers on different substrates like; iron, aluminium.

A Graphical User Interface (GUI) was created to help simulating the reflection and transmission coefficients. Any number of layer can considered.

Important parameters like frequency, probe geometry and coupling medium are also analysed for an adequate an accurate evaluation of layers. This technique has great potential to test laminates adhesion.  

 

    DETERMINATION OF MEAN GRAIN SIZE BY ULTRASONIC METHODS OF TUNGSTEN CARBIDE METAL MATRIX COMPOSITES SINTERED AT VARIOUS TEMPERATURES

 

İsmail Hakkı SARPÜN1, Vildan Özkan1, Sabri TUNCEL2, Rıdvan ÜNAL1 

1Afyonkarahisar Kocatepe University, Physics Dept. 03100 Afyonkarahisar, TURKEY

2TÜBİTAK Marmara Research Center Gebze, Kocaeli, TURKEY 

ABSTRACT 

In this study, the mean grain size of different ceramic-metal composites made from tungsten carbide (WC), aluminium (Al), nickel (Ni) and aluminium oxide (Al2O3)  powders, have been determined with ultrasonic velocity technique. In addition, electroless coating method was used to coat all samples. Prepared samples were sintered at the different temperatures ranging from 9000C to 1400 0C in an Argon atmosphere. Powders were placed in a 30mm diameter mold and pressed using a hydraulic press at a pressure of 300 bar.

The results were compared to the mean grain size obtained from SEM (Scanning Electron Microscopy). This work will show the relation between ultrasonic velocity and average grain size of samples. Mean grain size of samples will be calculated by the ultrasonic method and the optimum production conditions of the sintered phase will be determined from the temperature-mean grain size. 

 

    NON-CONTACT ULTRASONICS Used FOR impact DAMAGE DETECTION ON long-term water immersed GFRP COMPOSITES

 

K. Berketis, P. J. Hogg 

Queen Mary, University of London, London, UK 
 

Abstract: Traditional water immersion and Non-Contact ultrasonic C-Scan systems were used for damage detection and quantification on wet Glass Fiber Reinforced Polymer (GFRP) composites plates. Long-term immersion for up to 24 months, of low velocity impact damaged GFRP plates in hot water at 65º C and 93º C caused serious matrix and interface degradation. The water diffusion profile was followed by water uptake measurements. The use of water immersion single probe pulse-echo ultrasonics proved ineffective after long-term water immersion as damaged areas became ultrasound-invisible. The impact damaged part was filled with water thus acting in similar way to the rest of the undamaged material. The use of a pair of 400 kHz air-coupled through thickness ultrasonic probes was investigated for damage detection and evaluation. The contrast between impact damaged areas and water diffused areas was restored and damage size detection was possible. Calibrating the system for the group wave velocity of a dry condition specimen, a good qualitative and quantitative indication of the degraded state of specimens can be obtained. This system proved to be very promising for both the impact damage sizing and for the monitoring the degradation process. 

 

x, m

Investigation of accurate imaging of the defects in composite materials using ultrasonic air-coupled technique

 

R.Kazys, L.Mazeika, E.Zukauskas 

Ultrasound Institute, Kaunas University of Technology, Lithuania 

The modern aircrafts are built using different composite materials such as carbon/glass fibre reinforced plastics, GLARE and honeycombs. The composites structures are much lighter and possess similar or even better strength properties then the corresponding metal constructions. The manufacturing technologies of composite materials are complicated and include multiple stages. The small deviations from the technology parameters can cause relatively small defects, but influence of these defects on a total strength of a construction may be essential. So, due to the safety reasons they should be inspected during manufacturing and exploitation, using accurate non destructive testing techniques. 

  The conventional ultrasonic inspection techniques require liquid acoustic coupling, but wetting of the composites with coupling liquids in different manufacturing cases is unacceptable or even not allowed because they may cause additional technological failures. Because of that the ultrasonic air coupled technique is very attractive for inspection of composite materials. On the other hand, the complex structure of composite materials causes big losses and scattering of the signals. Additionally, the attenuation of ultrasonic waves in air increases with the frequency. Due to these facts the ultrasonic air coupled measurements are performed at lower frequencies, what leads to reduction of the spatial resolution and accuracy in ultrasonic imaging. So the objective of this paper was to present results of the investigation of accuracy of ultrasonic air coupled imaging of defects in various types of composite materials. 

  Detection of defects usually is based on attenuation of the longitudinal and Lamb waves in the defected areas. Such an approach reduces the reliability and accuracy of the inspection. On the other hand, the investigations carried out by us have shown that the complicated mode conversion phenomena take place in the defected areas and these places become the sources of other types of leaky waves. The exploitation the waves generated by interaction of longitudinal and Lamb types of waves with delamination type defects in aerospace components enables to develop the new, more accurate, ultrasonic testing techniques.

  Investigation of interaction of ultrasonic waves with delaminations and generation of mode converted waves was investigated for two cases: normal incidence of a longitudinal wave and propagation of the a0  Lamb wave inside the composite material.

  In the case of the through transmission technique the longitudinal wave was radiated and picked-up by the 460 kHz focused ultrasonic transducers, which were directed at 90o to the surface of the sample.  It was observed, that in addition to the plane longitudinal wave transmitted through the composite material, some additional regular signals exist which distort the ultrasonic B and C-scan images and reduce the accuracy of defect sizing. It was find out and proved by modelling and experiments that these signals are caused by additional guided a0  Lamb wave waves, excited in the composite by the focused ultrasonic transducers. These guided waves propagate around the defect and radiate various leaky waves into air. The interference of these waves with the longitudinal wave transmitted through the composite material creates some regular pattern in the 2D ultrasonic image. It was proposed to exploit these regularities for more precise determination of boundaries of defected areas.

 

    Phasor XS opens the door to Phased Arrays

 

Mr. Thomas Fausten

 

Technical Support Manager – Ultasonics

GE Inspection Technologies GmbH, Robert Bosch St. 3,50354 Huerth, ,Germany

tel:+49(0)2233601226, fax:+49(0)2233601324 

 

ABSTRACT 

Phasor XS is a simple to use, Ultrasonic Flaw detector with both conventional channel and Phased Arrays capability. This system provides a full color sector image and B-Scan. With one multiple beam scan from one contact location, greater area is covered and inspection data can be displayed as a traditional A-Scan, sector scan, or both simultaneously in real time. 

When compared to conventional ultrasonic inspection, the productivity, accuracy and cost savings gained by Phasor XS are endless. Time saving, higher confidence in results and increased probability of detection are the main advantages.  

Phasor XS includes a wide range of standard Array Transducers and has a lot of applications. It is quite useful especially in inspection of composites, pipes, weldings and railroad wheels. 

An overview of the Phased Array principles, the advantages, and the basic applications will be presented. 

 

 
 
 
 
 
 
 
 
 
 

 

SESSION 2

INDUSTRIAL RADIOGRAPHY  

    Neutron scattering techniques as a tool for non-destructive testing

 

K. Mergia, G. Apostolopoulos and A.G. Youtsos 

Institute of Nuclear Technology and Radiation Protection,

National Center for Scientific Research ��Demokritos��, Athens, Greece 

ABSTRACT 

Neutron scattering techniques constitute a powerful tool for non-destructive testing of materials. Neutron scattering techniques offer the advantage of high penetration into the matter and this allows the study of volume effects and bulky components. Compared to the commonly used X-ray techniques, neutrons have the advantage of distinguishing among different metals and are sensitive to light elements. Another big advantage of thermal neutrons is their high interaction probability with hydrogen which can be found in most of organic compounds.

Neutron diffraction technique is the most useful method for studies of structural changes of the crystal lattice particularly in the presence of heavy elements. It can be used for residual stress measurements in engineering components, for the diagnosis of the modification of irradiated materials, etc. Small-Angle Neutron Scattering (SANS) is actually a scattering method for detecting heterogeneities in the range from 1 to 1000 nm imbedded within a matrix of different neutron scattering power. SANS can be used from predicting failure in nickel-base superalloy turbine blades to a study of debonding of fibers in carbon-carbon fiber composites and to the study of cement hydration.

The neutron scattering facilities at the Greek Research Reactor are described in connecting with possible non-destructive applications.

 

 

    Dual-Energy Gamma-Ray Transmission Technique for Measurement of the Density of Mine Water Treatment Sludge during Sedimentation and Consolidation

 

Lincar Pedroni1, Gregory Kennedy2, Michel Aubertin1 

1Department of Civil, Geological and Mining Engineering, Ecole Polytechnique, Montreal, Canada

2Department of Engineering Physics, Ecole Polytechnique, Montreal, Canada 

ABSTRACT 

The technique of gamma-ray transmission has been used to measure the variation in density of a treated acidic mine water sludge as it settles during sedimentation and consolidation. A source and Sodium-Iodide detector are arranged to vertically scan a sludge-filled 180cm high Plexiglas column in a few minutes. The measured data are used to plot density profiles over time which can be used to help predict the long-term behaviour of sludge in mine tailings ponds.

This paper presents recent tests which have been performed using a single source of 153Sm and considering two energies (41-42keV and 103keV), in order to simultaneously determine the solids density and water content during sedimentation and consolidation of mine sludge with a low heavy metal content. A previous system using two sources, 153Sm (103 keV) and 198Au ( 412 keV), was found useful for determining the water content of  sludge with high heavy metal content but failed to distinguish between water and solids in sludge with low heavy metal content.

The dual-energy technique has achieved an accuracy of 0.04 g/cm3 for both solids density and water content in the sludge. However, the chemical composition of some sludge can limit the use of this technique depending on the gamma-ray energies used.

 

    Industrial radiography and tomography based on scanning linear scintillator array

 

L. Franco1, F. G��mez1, A. Iglesias1, F. Vidal2, R. Ameneiro2 

1USC, Universidad de Santiago de Compostela, Facultad de F��sica, Campus Sur S/N, 15704 A Coruña (Spain). Corresponding author: luciaff@usc.es, +34 981 563100 ext 13547.

  2AIMEN,Asociaci��n de Investigaci��n Metal��rgica del Noroeste, C/Relva Porriño-Pontevedra (Spain).

 

ABSTRACT

 

We are developing an industrial computed tomography system for non destructive testing of large pieces (maximum size 100 cm x 100 cm). The source is a tungsten X-ray tube (225 kV), and the sensor is a linear array of one meter length  with 1280 readout channels of submilimetrical pitch (0.8 mm).  The detector is based on scintillator coupled to a photodiode matrix of high efficiency.  Charge from each photodiode is integrated through a VLSI readout chip (XCHIP in XDAS board from Electron Tubes Ltd.) and digitized and sent to a fast digital I/O frame-grabber. The main aim of this system is NDT of metallic pieces, specially oriented to welding Quality Assurance.

 

The mechanical assembly integrates two motorized linear stages, both vertically positioned, and a motorized horizontal rotary stage. This assembly allows a synchronized linear translation of the x-ray tube and the sensing line, while rotating the object of interest. The rotary stage is mounted on another horizontal linear stage, to be able to adjust manually the radiation source – object distance in order to obtain a variable magnification. This multiaxial positioning system of flexible configuration is programmed in CNC using a PID controller, and it is integrated with the acquisition system via a software programmed in LabVIEW in a dedicated personal computer.  

The system allows three different acquisition modes: planar radiography, single axial slice and complete multislice computerized tomography. An automated calibration algorithm (air scan) was implemented, which corrects detector signal for individual channel gain and offset.

 
 
 

Figure 1. Planar radiography of a weld (left) and developed CT system prototype (right).

 
 
 
 
 
 
 
 
 
 
 
 
 

A demonstration prototype with a 50 cm long (0.8 mm pitch) linear array and a 50 kV X-ray tube of 100 W and 0.1 mm focal spot has been built. Image resolution in planar radiography and tomographic slices has been analyzed. Detector spectral sensivity, crosstalk signal from adjacent channels and direct signal from photodiode semiconductor wafer have been measured and characterized.

 

 

    Non-destructive compositional analysis and materials characterization with portable X-ray fluorescence analyzer��s (XRF)

 

T. Houlahan1, B. Allen2 

1Thermo Fisher Scientific, Niton Europe GmbH, Munich (Germany); +49 89 3681 380

Niton.eur@thermo.com, www.thermo.com/niton

2Niton LLC, Billerica (USA) 

ABSTRACT 

Portable X-ray fluorescence analyzer��s versatility and accuracy have made it the standard for on-site non-destructive compositional analysis and materials characterization in a variety of materials. Their portability and speed allow for rapid testing wherever it may be needed. It is also popular for quality control of alloys, ceramics and for prohibited materials screening (e.g. for tin whisker prevention) of electronics.  

Recently, the European Union (EU) has mandated a switch to the use of lead-free solder in the electronic assembly process. A date of July 2006 has been set as the deadline for all electronic products sold in EU member countries to be lead-free. In addition to verification of lead-free solder, the NITON analyzers can also be used as screening tools for toxic elements (lead, mercury, cadmium, chromium and bromine) in plastics as part of the same EU directive. 

Flow-accelerated corrosion, or FAC is a well-known source of problems in nuclear and fossil-fuel power plants. Small quantities of alloying elements - particularly chromium - greatly reduce the rate of FAC. Recent advancements in handheld XRF technology have resulted in dramatically improved detection limits, which now make XRF a valid alternative method for FAC analysis application. These applications and a brief history of portable XRF will be offered.   

In addition a new portable XRF instrument with an internal helium purge system has been developed.  This invention expands portable XRF��s compositional analysis capabilities into alloys containing critical amounts of the lighter elements like Al, Si, Mg, and P.  The technology, capabilities, and limitations will be presented and discussed as well.

 

 

    DEVELOPMENT OF NEW X-RAY RADIOSCOPY & Tomography EQUIPMENT FOR NDT ANALYSIS

 

Mihai Iovea1, Gabriela Mateiasi1, Marian Neagu1, Vassilis Georgiou2,

Panagiota Tsagkari3, Antonios Antonakakis3 

1ACCENT PRO 2000 Ltd., www.accent.ro; office@accent.ro

2�������� SA

3Public Power Corporation, KDEP, Greece 

ABSTRACT 

Based on previous simple X-Ray tomograph developed at PPC some years ago, we continue the R&D program by building new Radioscopy & Tomography equipment based on using a new 1280 x 0.4 mm X-Ray Linear array detectors and 300 keV/5mA X-Ray generator. The vertical translation with 250 mm range and a 200 mm diameter-rotating table allows tomographic reconstruction (slices) at any height and also digital radiography scans at any angle. The paper presents the general design and the main features of the new system together with the preliminary tests. 
 
 
 
 

 

    Successful conversion from Film to Computed Radiography

 

Peter Deschepper 

Technical Support Management - Digital Systems

GE Inspection Technologies, ��De Veldekens�� Roderveldlaan 5, B-2600 Berchem, Belgium

Tel: +32(0)34562820, Mobile: +32(0)479640075, Fax: +32(0)34562870

Peter.deschepper@ae.ge.com, www.GEInspectionTechnologies.com 

ABSTRACT 

Digital Radiography using storage phosphor plates is known as ��Computed  Radiography�� or CR for short.  This ��film-less�� technique is an alternative for the use of medium to coarse-grain X-ray films.   In addition to having an extremely wide dynamic range compared to conventional film, CR-technique is much more sensitive to radiation, thus requiring a lower exposure dose.  This results in shorter exposure times and a reduced safety area. 

In addition to the reduced cost on consumables, the return on investment of CR systems is strongly determined by savings in exposure time, processing times and archival times. But also intangible costs like plant shutdown, environment safety and longer usability of isotopes are increasingly important when considering replacing film by Storage Phosphor systems. 

More than in traditional radiography, the use of digital images is a trade-off between the speed and the required quality. Better image quality is obtained by longer exposure times, slower phosphor screens and higher scan resolutions. Therefore, different kinds of storage phosphor screens are needed in order to cover every application.  

Most operations have the data, associated with the tests to be performed, centrally stored in a database. Using a digital radiography system gives not only the advantages of the manipulation of digital images, but also the digital data that is associated with it. Smart methods to associate cassettes and Storage screens with exposed images enhance the workflow of the NDT processes, and avoid human error. Automated measurements tools increase the throughput in different kinds of operations.  

During the fall of 2005, the ASTM 2445/2446 and the European Standards EN 14784-1/2 have been published after long years of discussion. The standards describe a measuring method and a classification for CR systems, together with the different test classes in function of the material thickness and used energy. These publications broaden the application field of Computed Radiography. One of the applications waiting for standardization is the radiographic inspection of welds. Weld inspections cover more than half of the applications in the oil and gas market, and replacing film by Computed Radiography would bring total cost savings to the inspection company.

 

 
 
 
 
 
 
 
 
 

 

SESSION 3

ARTWORKS AND MONUMENTS NDT  
Laser profilometry and flash thermography for surface roughness assessment of Pentelic marble

 

    A.Moropoulou, E.T. Delegou, N.P. Avdelidis  

    National Technical University of Athens, Laboratory of Materials Science & Engineering, Iroon Polytechniou 9, 15780 Zografou, Athens, Greece 

    ABSTRACT 

Laser Profilometry is one of the most recently developed approaches for the description of surface micro-topography and roughness. In this work, tree dimensional laser profilometry (LP) was employed for the assessment of surface topography of Pentelic marble samples. Quarry samples differently abraded and /or processed, as well as collected monument samples after pilot cleaning interventions, were evaluated in lab. The surface topography assessment was characterised by the Rq roughness value that is the root mean square deviation of the assessed profile. Moreover, 3D micro-topography plots from the LP were obtained. Results indicated that the performed quantitative analysis by the LP scanning approach can be used for the assessment of surface roughness and micro-topography on Pentelic marble samples.  
 

 

 

    NDT of Wood, for a real Sustainable Development

 

Jean-Luc Sandoz, Yann Benoit

 

    Monitoring of Fissures on Constructi on Trogir's Cathedral of St Lawrence (Sv Lovro), Croatia

 

Tanja Roje-Bonacci 

University of Split, Faculty of civil engineering and architecture, Matice hrvatske st. 15

HR – 21000 Split, Croatia 

ABSTRACT 

Building of Trogir's Cathedral of St Lawrence (Sv Lovro) started in 1193 and finished around 1500. The most notable features of the church is an Romanesque door carved around 1240 by Master Radovan. The Cathedral features a 14th century bell tower 47 m high. In the Cathedral is the Renaissance Chapel of St. Ivan. The decorations within the chapel were created from 1461 to 1497 by Firentinac and Duknovic.

On the walls of the Cathedral multiply repaired fissures were noticed.  These fissures are still existent. As it was decided that the construction needs a major repair, the works were preceded by instrumental monitoring of most obvious fissures. At the same time, air temperature and humidity within and outside the construction were measured. Devices used enable permanent reading of the fissure parameters, but the readings are taken only with period of one day or less. Devices were set up by the Italian Company SER.CO.EC. of Trieste. Monitoring was organized and conducted by regional office of the Croatian ministry of culture in Split. At first observations were recorded daily, but as it was found out that this was too frequent, this frequency was reduced. Initially, eleven sensors were used.

Recorded data are presented as statistically observed time series. The results of this observations points on issue of the fissures. Some where connected with air temperature, some with past reparations works on construction.

 

    Non destructive identification of the colouring substances on the monuments

 

M. Kartsonaki1, M. Koui1, P. Callet2 , E. Cheilakou1 

1National Technical University of Athens, School of Chemical Engineering, Section of Materials Science and Engineering, Iroon Polytechniou 9, 15780 Zografou, Athens, Greece.

2Ecole Centrale Paris, Systems Applied Mathematics Laboratory,Grande Voie des Vignes F-92295 Châtenay Malabry. 

* Corresponding Author, email: markoue@chemeng.ntua.gr 

Abstract 

The identification of the colouring substances of historical monuments and masterpieces, is of great interest to archaeologists and historians of art allowing in a first place its right positioning back in time and in a second place the comparative contemplation of painting procedures and materials used in different places and periods. However, the anciennity and the historical interest of monuments, sometimes do not allow the possession of samples and thus for such a study we should refer to analytic non destructive methods.  

Our work was carried out in the frames of a complete effort of maintenance and restoration of the colours of the monument of Philippe Dagobert (1222-1232) exhibited in the cathedral of Saint Denis in Paris, the greatest necropolis of the medieval times. It��s about one of the most characteristic samples of medieval funerary art, still presenting coloured traces referring to the stimuli of blue, red, green and yellow. 

For the determination of its chromatic identity we used in situ and in lab a UV-VIS-NIR  spectrophotometer (Ocean Optics USB2000), a method visualising the result of the interference of the light with a coloured surface and capable of reproducing correctly the three primary stimuli R (red), G (green), B (blue) responsible for the erection of human optical cells.  

The bibliographic research provided information about the colouring substances used in Middle Age and their preparation before their application on the working surface that we reproduced in the laboratory. The measurements carried out represent the distribution of the intensity of the reflected  light by the coloured surface. Conclusions were carried out by comparing the calculated distributions of the measurements taken in the laboratory and in situ.   

From the results related to the chromatic identity of the monument, we concluded that the blue stimuli comes from a mixture of equal concentrations of azurite and malachite, the green ones are due to a mixture of malachite and green earth (equal concentrations too) and the red and yellow ones, are probably related to a red and yellow ochre presenting signs of aging.

 

    Recordings and analysis of electric signals emitted during bending processes on rock (marble) beams

 

C. Anastasiadis, D. Triantis, I. Stavrakas, A. Kyriazopoulos, P. Kyriazis 

Materials Research Laboratory, Department of Electronics, Technological Educational Institution of Athens, 12210, Athens, Greece 

Abstract 

Laboratory experiments for the detection of electric signals (Bending Stimulated Currents - BSC), have been conducted on marble beams by application of a three point bending technique. Twelve successive abrupt stepwise loadings at a rate of 1kN/s were applied upon the samples under investigation up to final failure with simultaneous recording of the emitted BSC using a pair of electrodes positioned on the lower surface of the beam. ��he BSC measurements were achieved using a sensitive programmable electrometer. During each abrupt stepwise loading a BSC peak appeared and while the load was getting a stable final value the BSC relaxed decreasing at an exponential law. The peak value and the time constant of the BSC relaxation for each stepwise loading are correlated with the corresponding individual load. The qualitative results of these correlations push forward a fatigue criterion of the sample.

 

    Evaluation and mapping of concrete and rebar condition with the GPR method of an old building facing daily extreme strain

 

Michael S. Arvanitis 

Geomorph Instruments, Tsamadou 38, 18531, Piraeus, Greece  info@geomorph.gr 

ABSTRACT 

We employed Ground Penetrating Radar (GPR) technique in order to assess firstly and then to map the concrete condition and the rebar of an old building, used as a coach house by an important cars importer in Greece. The owners wanted to build a new section on the top of the existing building in order to store hundreds of cars and trucks. The building was erected by the mid of 1970��s and has responded quite well to the big earthquakes of 1981 and of 1999. 

We used a GSSI Ground Penetrating Radar, which gives data of high quality and precision and processed this using the Radan 6 post-processing software. The antenna of the GPR had a frequency of 1600 MHz, assuring a depth penetration of 20 – 50 cm depending on the material. With this high-resolution antenna, we could locate even small targets in real-time. Only single sided access is required to perform GPR surveys, and thousands of square meters can be inspected in one day. This method is also extremely safe and does not require evacuating areas as with radiography (X-ray) while X-ray can not find non-metallic utilities buried within concrete like GPR technology can, and measuring depth of targets with X-ray can be difficult. We employed 30 GPR sections all over the building, focusing mainly on the most important parts, like pillars, flat roof surface and joints. 

The final results showed accordance with the samples that have been taken and indicated with accuracy the points that need restoration. 

References: 

Davis, J., Huang, Y., Millard, S.G., Bungey, J.H., Determination of dielectric properties of insitu concrete at radar frequencies. BAM International Symposium (NDT-CE 2003).  

Robert, A., 1998. Dielectric permittivity of concrete between 50 MHz and 1 GHz and GPR measurements for building materials evaluation, Journal of Applied Geophysics, 40, 89-94.  

Annan, A.P. and Davis, J.L., 1977. Radar Range Analysis for Geological Materials. In Report of Activities, Geological Survey of Canada Paper 77-713, 117-124.  

Topp, G. C., Davis, J. L. and Annan, A. P., 1980. Electromagnetic Determination of Soil Water Content: Measurements in Coaxial Transmission Lines, Water Resources Research, Vol. 16, No. 3,574-582.

  

 

 
 
 
 
 
 
 
 
 

 

SESSION 4

INDUSTRIAL APPLICATIONS - 1

 

 

Development of a comprehensive in-line quality control system for printed circuit board assemblies 

P I  Nicholson and P Wallace 

TWI Ltd, Cambridge, UK, CB1 6A1

Tel: +44 (0)1639 873100, Fax: +44 (0)1639 864679

Email: ian.nicholson@twi.co.uk 

ABSTRACT 

Printed Circuit Boards (PCBs) are widely used in electronic goods and many applications that require microprocessor controls. The need to increase the population density of components on PCBs, to make the products ever smaller, has driven the move to more complex surface mount assembly technology. This has led to increased use of area array components such as Ball Grid Arrays (BGAs) and other small footprint devices. As a result there are greater demands on Non Destructive Testing (NDT) examination for quality assurance. Using just one inspection technique, it is not possible to reliably detect all types of PCB assembly defects. In this paper we describe the development of a PCB inspection system that combines four different NDT techniques, based on Automated Optical Imaging (AOI), Digital Radiography (DR), Thermography, and Scanning Acoustic Microscopy (SAM). Each technique has been modularised and the final prototype takes the form of a conveyor belted production line. It is the first time anywhere that the four techniques have been combined together in-line to offer the possibility of 100% defect detection. The application of each NDT technique, the integration, the results and the proof in principle are presented. 
 
 
 
 

Figure 1 Conceptual drawing of in-line PCB inspection system

 

    Inspection of turbine blade bolts

 

Carlos Desimone, Pablo Katchadjian 

CNEA, Argentina 

ABSTRACT 

Bolt are coupling the blades on the turbine. Ultrasonic in service inspection is developed from an axial bolt bore hole aiming the beam to the outer surface to detect transversal defects along the bolts. In this presentation are described the techniques used. One is a contact technique employing an angular transducer with manual or automatic driving by a device with oscillating rotation and axial movement. The second one is by immersion technique using an ultrasonic tool with an axial transducer aiming the beam into the material by reflection in a rotational mirror, driving it by a flexible coupling and external motor. The techniques have been applied in several inspections of bolts in Kaplan turbine blades of a hydroelectric power station. Both tests can be fully automated to control scanning parameter, data recording and presentation and post signal treatment.

 

 

    The Hull Inspector Project: An Investigation of technologies for Non-Destructive Testing of ship hulls

 

Joseph M. Buckley1, Bruce Blakeley2, Doug Breeze2, David Parramore3, Ioannis Seisakis4, Dimitrios Korres4 

1Sonatest Ltd, Milton Keynes, England

2TWI, Cambridge, England

3TSC Inspection, Milton Keynes, England

4Zenon, Athens, Greece 

ABSTRACT 

[N.B. This is not a final abstract, It has not yet been approved by the project consortium, It is supplied only for assessment of possible inclusion in the conference. A final approved abstract will be supplied as soon as possible] 

Ship hulls are large, and necessary inspections for corrosion and weld cracking are laborious and time consuming. The ideal would be to have an autonomous robt which can carry out these inspections automatically, and if possible, while the ship is in the water. 

The Hull inspector project was conceived to investigate some of the necessary technologies to progress toward this aim. A ��crawler�� was developed, capable of accommodating a wide range of inspection techniques, including standard and phased-array ultrasound, magnetic flux leakage, and alternating current field measurement (ACFM

This paper will outline the approach taken in the project, discuss what was achieved (and what was not) and detail some of the lessons learned from it.

 

    Integrating Risk Based Inspection into Plant Condition Monitoring Software

 

A.Anastasopoulos & J. Redmon 

ABSTRACT

 
Risk Based Inspection is often used as one-time study as a mean to prioritize inspections for the T/A. Inspection history and NDT data from PCMS are needed for the RBI study. On the other hand, the RBI results are used for the T/A plan but then just sits in a binder or CD, and never used 
again.  Thus the real issue is in the way these two types of data are integrated into one database for maximum use by the customer.  The PCMS Integrator module addresses these issues. Within this framework the paper demonstrates how the NDT and corrosion management data captured on a daily basis are integrated for the RBI assessments and how the RBI results are used for planning

 

    Towards robotic non-destructive inspection of industrial pipelines

 

P. Chatzakos1,2 , Y. P. Markopoulos1, D. Korres1, V. Spais1, G. Sisakis1, N. Chatzinikolaou1 and K.Hrissagis1 

1ZENON S.A, 5 Kanari Str, Glyka Nera Attikis, 15354 Athens, GREECE

 2NTUA, Department of Mechanical Engineering, 15780 Athens, GREECE 

Abstract 

Keywords: mobile robotics, omni-directional robot, external-pipe crawler, automated inspection,

NDT scanner. 

In this paper, the development of a novel omni-directional inspection robot is presented, which is capable of delivering NDT sensors to surfaces on straight pipe, pipe bends and branch connections, overcoming the limitation that a test area over a pipe bend or past a branch or other obstruction raise. The lightweight crawler is attached on the outside of the pipe to the thin metal strip that holds the insulation in place without deforming the insulation through the application of a force controlled clamping mechanism while performing longitudinal, circumferential and arbitrary movements. In order to be able to cope with a range of pipe, materials and coverings, to allow for future modifications and to be able to incorporate a wide range of NDT inspection equipment, a modular approach was considered for the design of the mobile robot. Either two different inspection sensors may be mechanically incorporated into the chassis of the crawler and deployed at the same time or just a double-sided acting sensor (e.g. X-Ray). 
 
 
 

 

    PERFORMANCE ASSESSMENT OF PENETRANT AND MAGNETIC PARTICLE SYSTEMS USED AT HELLENIC AEROSPACE INDUSTRY

 

Roubini Marini1, Paraskevas Ranos2, Athanassios Dimopoulos3

 

1Special Processes & Labs Dept, Hellenic Aerospace Industry S.A. P.O. Box 23, 32009 SCHIMATARI-GREECE

2NDI Shop, QC Engines Dept., Hellenic Aerospace Industry S.A. P.O. Box 23, 32009 SCHIMATARI-GREECE

3NDI Level 3 Responsible, Hellenic Aerospace Industry S.A. P.O. Box 23, 32009 SCHIMATARI-GREECE 

ABSTRACT 

In the aerospace industry, Non-Destructive Testing (NDT) and Inspection (NDI) are vital functions in achieving the goals of efficiency and quality at an acceptable cost. In many cases, such as in Penetrant Testing and Magnetic Particle Testing, where these functions are highly critical, the reliability of the method depends a lot on the performance of the means (penetrant and magnetic system), as well as on operator reliability, because observing of results is made visually.  

The NDI facility is performing process control operations or contracting for their performance with an independent laboratory. On the other hand, all penetrant materials shall conform to the requirements of SAE AMS 2644, whereas all magnetic particles materials shall conform to SAE AMS 3044 or SAE AMS 3045 or SAE AMS 3046. This conformance is verified by a report from the supplier. However, conformance does not always assure efficiency; thus, performance tests are prerequisite to assess the applicability of the systems at the HAI��s NDI facility. 

In the present paper the performance of different penetrant and magnetic particle systems is assessed aiming at the optimization of the method used. The testing efficiency of different products used for everyday NDI in Hellenic Aerospace Industry is discussed. Some results of investigations based on standardized test panels evaluation, which enable increasing the efficiency of both methods, are presented.  

 

 
 
 
 
 
 

 

SESSION 5

COMPOSITE MATERIALS AND NDT 

    EXAMINATION AND MONITORING of CARBON-EPOXY COMPOSITES STRUCTURES

 

Raimond Grimberg1, Adriana Savin1, Sorin Leitoiu1, Nicoleta Iftimie1,

Alina Bruma2, Aurel Andreescu1 

1 Nondestructive Testing Department, National Institute of Research and Development for Technical Physics,47 D. Mangeron Blvd., Iasi, 700050, ROMANIA

2Faculty of Physics, Al.I.Cuza University,11 Carol I Blvd., Iasi, 700506 Romania 

ABSTRACT 

      Given their specific characteristics, the carbon-epoxy composites are used in different application, from airspace industry to sporting goods. As compared to the metallic materials, carbon-epoxy composites show a series of advantages, among which a high tensile strength, low density and thermal expansion coefficient, absence of phenomenon specific to the fatigue state, possibility of a relatively simple manufacturing of large layered structures. Yet, one of their major disadvantages one should mention is the reduced resistance to impacts that can induce- depending on their energy- fiber shift or delamination, even fractures.

      The carbon-epoxy composites present electrical properties that depend on the type of the used carbon fiber in their volume fraction of material.

      To detect the damaged region, we propose the utilization of two complementary methods: eddy-current technique using focused transducers and ultrasound sensors array [1], [2]. In the purpose of a precise quantification of the area of delaminated region as consequence of the impacts, a special technique of data fusion was developed [3].

      For monitoring of the carbon- epoxy composites, we propose the utilization of the Bragg fiber grating, the way of impact positioning and the determination of the delamination area induced by these causes being presented.

      Using the proposed data fusion method, impacts with minimum energies of 2.5 J can be detected, the area of the delamination being different with less that 12% comparing with C- scan U.S.

      This method of monitoring also assures correct estimations, in good concordance with those obtained with the proposed detection methods. 
 

References: 

  1. R. Grimberg, D.Pr��mel, A.Savin, Y. Le Bihan, D.Placko, Eddy Current Holography Evaluation of Delamination in Carbon – Epoxy Composits, INSIGHT 43,4, UK,(2001), p.260-264
  2. R. Grimberg, A. Savin, R. Steigmann, A. Bruma, Eddy current examination of carbon fibres in carbon-epoxy composites and Kevlar, International Journal of Materials and Product Technology,vol.27, nos.3/4,  2006, pp.221-228
  3. Raimond Grimberg, Rozina Steigmann, Sorin Leitoiu, Aurel Andreescu, Adriana Savin Ultrasound and eddy current data fusion for evaluation of carbon-epoxy composites delaminations, Emerging Technologies in Non-Destructive Testing, ETNNDT Fourth International Conference, April 2-4, 2007 Stuttgart, Germany
 

This paper is supported by Romanian Ministry of Education and Research - Research of Excellence Program, Contract No.49/2006 ROLIGHT. 

    acoustic emission inspection and analysis of crimped metal composite joints subjected to bending

 

A. Prenleloup1, T. Gm��r 1*, J. Botsis1, K. O. Papailiou2, K. Obrist2 

1 Ecole polytechnique f��d��rale de Lausanne (EPFL), STI – LMAF, 1015 Lausanne, Switzerland

2 Pfisterer-Sefag AG, Werkstrasse 7, 6102 Malters, Switzerland

* Corresponding author: Thomas Gm��r (thomas.gmuer@epfl.ch) 

Abstract 

Nowadays, mixed composite-metal joints are increasingly used in industrial equipments such as automotive, aircraft, aerospace or electrical components. As a specific application of mixed joints encountered in high-voltage networks, silicon composite insulators with crimped metal end-fittings manufactured for high-voltage transmission lines are now replacing conventional porcelain elements. These structures, however, require two metal end-fittings in order to transfer loads from the high-voltage conductor to the tower.

Among the different issues concerning the reliability of these joints, three are considered very important. These are: (a) the distribution of stresses on the joint, (b) the efficiency of the interface between the metal and the composites, and (c) fatigue and fracture of the composite under different external mechanical loads. In this work, numerical simulations of the stress distributions throughout the joints are performed by means of full 3D finite element models. An experimental setup based upon acoustic emission and strain gauges is also developed in order to validate the numerical models and to follow the damage progress in the joints. The results of the experiments and simulations are used to optimize the mechanical bearing capacity of the insulators.

Experimental bending tests are performed on several joints made of epoxy-glass laminated rods with a diameter between 51 and 88 mm and of two steel end-fittings crimped to the composite component by a radial compression until a sufficient plastic deformation is initiated in the metal. In order to follow the evolution of the local deformations during loading, eight strain gauges are pasted on the composite rod and on the end-fittings at various locations. An acoustic emission set-up with 8 channels is used in parallel for monitoring the damage progress as a function of the applied bending load.

Several finite element models are also developed in order to characterize the internal stresses in the joints. The numerical simulations have highlighted the complexity of the nonlinear stress state in the composite rod and have illustrated the different damage mechanisms which may occur simultaneously or separately (longitudinal crack propagation due to the shearing stresses and/or transverse crack propagation due to the normal stresses). These predictions are validated by the experimental results     as shown in Figure 1 where the two zones of crack propagation can be observed. 

zone 1

zone 2

 

Fig. 1 Longitudinal (zone 1) and transverse (zone 2) crack propagation in the composite rod.

 

    Application of Ultrasonic C-Scan Techniques for Tracing Defects in Laminated Composite Materials

 

Badogiannis E.1, Hasiotis T., Badogiannis E1. and Tsouvalis N. 

NATIONAL TECHNICAL UNIVERSITY OF ATHENS

School of Naval Architecture and Marine Engineering

Shipbuilding Technology Laboratory

1 Corresponding author;  Heroon Polytechniou 9, GR-157 73 Zografos, Athens, GREECE;

  email: badstrat@central.ntua.gr 

ABSTRACT

 

 

In this paper practical ultrasonic C-scan techniques for NDT examination of laminated composite materials are developed and applied, aiming at tracing specific artificial defects. Two types of materials are examined, namely an advanced carbon/epoxy system with unidirectional fibers and a typical marine type glass/polyester system with woven roving fibers.  Both materials were used in association with two manufacturing methods, namely the simple Hand Lay Up method and the more advanced Vacuum Infusion one.  Several artificial defects made of Upilex polyamide material were embedded into the 14 layers test plates.  These defects have varying shape and magnitude, as well as varying through thickness position, overlapping between each other in one case.  A typical layer wrinkle was also manufactured at mid-thickness in each test plate.  Test plates were C-scanned using an UltraPack II ultrasonic system in association with UltraWin software and incorporating different transducers.  The determination and characterization of defects was attempted by applying already known examination techniques, such as layer to layer examination, full width examination, etc.  However, software tuning procedures and appropriate examination strategies were applied, in order to further develop and optimize the scanning procedure.  These efforts resulted in effective C-scan images (see a typical example in the attached Figure), allowing the precise determination of the size and the position of all defects.  Finally, precise determination of specimens�� width was also achieved. 

Key words: Composites, Ultrasonic, C-scan, Defects

 

    Ultrasonic guided waves for health monitoring of high pressure composite tanks

 

M. Castaings, B. Hosten

 

Laboratoire de M��canique Physique, UMR CNRS 5469, 351 cours de la Lib��ration, Universit�� Bordeaux 1, 33400 Talence, France. 

Abstract 

Keywords: Guided waves, NDT, composite tanks. 

Ultrasonic guided wave modes are proposed to control the integrity of high-pressure composite tanks produced by EADS - ASTRIUM, France. The purpose is to demonstrate the potentiality of air-coupled transducers to set-up a contact-less, single-sided technique for testing the moisture content and/or the micro-cracking of carbon epoxy composite wound around a Titanium liner, as well as to detect local disbonds between the composite and the liner. First of all, a laboratory experimental system and numerical tools are used to quantify the sensitivity of specific parameters (wavenumbers or attenuations) of some modes to the moisture content and to the micro-cracking in composite plate samples. These results are then used to set an experimental strategy for testing the carbon epoxy component of a high pressure composite tank, and the use of air-coupled transducers for generating-detecting sensitive wave modes is demonstrated. Secondly, the air-coupled system is employed for detecting a local disbong in the tank, simulated by a Teflon insert. 
 

This work was supported by EADS - ASTRIUM and Conseil Regional Aquitain, France.

 

    Prediction of Polymeric Composites Materials�� Residual Strength after Damage due to Different Damage Sources

 

G.C. Papanicolaou*, A.G. Xepapadaki 

Composite Materials Group, University of Patras, Department of Mechanical and Aeronautical Engineering, Section of Applied Mechanics, Patras-265 00, Greece 

*Corresponding author, email: gpapan@mech.upatras.gr 

ABSTRACT 

All structural components when under working conditions, are subjected to damages resulting to respective deterioration of their mechanical response. The type and the extent of damage depend not only on the materials�� structure, but also on the working and general environmental conditions. The main causes, for damage development in polymeric materials, are: water absorption (or moisture) from the environment, random simple impact, repeated impact, mechanical, thermal or hydrothermal fatigue and any combination of the above-mentioned damage sources. As a result, damage deteriorates polymeric materials�� response and occasionally their fracture behavior. In the present investigation, several factors responsible for damage development in polymeric composite materials as well as their consequences on the mechanical degradation will be studied. In addition, prediction of the said degradation due to damage is presented and predicted by simply applying the RPM model (Residual Property Model). As it will be shown the Model predicts the material��s behavior after damage independently of the source which creates the damage.  The RPM model has already been successfully applied in a series of experiments in order to compare predicted values with experimental findings. For the application of the Model only one experimental point is needed to predict the whole variation of the mechanical properties of polymeric materials as a function of the extent of damage and/or respective energy independently of the damage source. Thus, the model works almost as an NDT method due to the very limited number of input data needed for its application. The prediction is valid up to a limit above which linearity does not apply anymore. 
 
 

 

 

    Semi-Static Crack Detection in Composite Materials by Magnetoelastic Alloy Strips

 

Dionysios E. Mouzakis1 D. Dimogianopoulos,  and Dimitrios Kouzoudis2 

1Department of Materials Science, University of Patras, Greece, RION, GR 26500, email: mouzakis@upatras.gr

2Department of Engineering Sciences, University of Patras, Greece, RION, GR 26500 

ABSTRACTemail: 

Introduction

In Magnetoelastic materials the magnetization is stress dependent. Time dependent stresses such as those produced during crack formation induce corresponding changes to the magnetization of the material which can be detected non-destructively and wirelessly by and external pick-up coil [1]. The induced voltage on the coil is amplified and collected by a digital oscilloscope. The stored signal is filtered for unwanted noise and processed in order to get crack-specific information. 

Materials & Experiental Procedures

A 2 mm thick glass fibre reinforced polyester plaque (GFRP) was cut into two rectangular specimens of mm 4.5 x 20 cm by a diamond saw. Afterwards theThese specimens were pre-cracked half way along their long side by incorporating two identical parallel notches on each side of the specimen edge producing thusmaking them Deeply-Double Edge Notch Tensile Specimens (DDEN-T). Thin 2.5 cm x 6.5 mm x 30 ��m stripes of magnetoelastic alloy Metglass supplied by HITACHI METALS were attached in the vicinity of the cracksBy as cracking sensors by using a two component epoxy glue (BISON) thin stripes of magnetoelastic alloy (Metglass) supplied by��������. were attached in the vicinity of the cracks respectively, as cracking sensors. In one of the specimentsspecimens the sensor was placed along the crack and on the other specimentspecimen it was placed 2 cm away. An Instron Universal Testing Machine was used in order to perform semi-static tensile loading at 1 mm/min on the DDEN-T specimens with the attached magnetoelastic ribbons up to specimen rupture. The EMF signal for all specimens during tensile loading of the specimens was remotely collected (contact-free) by means of a detection coil located over the samples.

.

ResultsMetglass ribbons were attached both perpendicularly and parallel to the initial notching direction respectively.

We have used a magnetoelastic metglass strip to detect the crack propagation in a glass fibre reinforced composite with success. This measurement was performed in a non-contact, remote detection mode. This technique is very promising for the construction of new generation smart composites with self damage detection characteristics.  
 

LiteratureReferences: 

  1. Kouzoudis D. and Mouzakis D.E., A 2826 Metglass Ribbon as A Strain Sensor for Remote and Dynamic Mechanical Measurements, Sensors and Actuators A, v. 127, pp. 355-359, 2006.
 

ResultsIn Magnetoelastic metrials the magnetization is stress dependent. Time dependent stresses such as those produced during crack formations, induce corresponding changes to the magnetization of the material which can be detected non-destructively and wirelessly by and external pick-up coil. The induced voltage on the coil is amplified and collected by a digital oscilloscope. The stored signal is filtered for unwanted noise and processed in order to get crack-specific information.Literature

 

    ELABORATION AND CARACTERISATION OF CARBON/EPOXY AND GLASS/EPOXY COMPOSITE STRUCTURE USED IN AERONAUTICS

 

FACI Youcef, Mme ABIDA Satour1, M.   BADIDI Bouda Ali2, BENREDJEN Djamel3 

Centre scientifique et technique en soudage et contrôle, Bp 64 Route dely Brahim CHERAGA   ALGER ALGERIE

Tel /fax : 00 213 021 36 18 50

Email    : faciyoucef@hotmail.com 

Abstract 

Keywords: Composite materials–ultrasonic sound - fiber of carbon–fibreglass

 

We have fixed as an objective in this work the characterization by ultrasonic method of composite material used in the aeronautic industry.

The work can be resumed as:

       - Elaboration of the composite material in fibreglasses epoxy and carbon epoxy for different thickness (1 to 6.5) mm and for orientation angle of (+ -  45)�� and (+ - 60��).

       -The research of the ultrasonic parameter which  characterise materials such as the velocity  propagation and the coefficient of  attenuation of the ultrasonic waves  in transmission  and reflection mode of the elaborated sample.

 

The results obtained: 

- The  coincidence of our results with those from the literature. 

- The application  of the method for the very absorbing material characterization.  

 

 

 

SESSION 6

ULTRASOUNDS-INDUSTRIAL APPLICATIONS - 2

 

Long Range Ultrasonic Testing of Pipes and Rails

 

Krasimir Staykov, Damyan Ganchev, Svetoslav Kutzarov, Bogomil Yochev 

ABSTRACT 

Application of guided waves for rail inspection in railroad industry is considered in the paper. NDT evaluation of rails using high frequency ultrasound (US) is relatively good developed and used in practice. Basic disadvantage of this technique is connected with the attenuation of ultrasound in the welded zone due to the microstructure of the alumino-thermic weld. Additionally, the working distance of US waves propagation is short and time of inspection is relatively long.

In the paper presented a low frequency US approach is considered. It is shown that operating frequency should be less than 100 kHz. Advantage of these waves is that at such frequencies material attenuation due to grain boundary scattering is very low and weld material can be easily penetrated and tested. US propagates long distances without significant attenuation hence a long range technology (LRT) is used.

The complications of using LRT are connected with the special shape and dimensions of rail. There a number of guided wave modes that can exist in such complex structures. All of them are propagating at different, frequency dependent, velocities. After mathematical and experimental considerations are taken into account, the optimum frequency for the given rail, is estimated to be around 70 kHz.

Dispersion curves and mode shapes for guided waves in rails were calculated using finite element technique. Novel transducers were designed which produce in-plane displacements. For damping of the transducers a specially designed backing material composite was used in order to reduce the ringing effect of the piezo element at low frequencies. Experiments were conducted using a single transducer and array of four transducers. Different materials were evaluated for dry-coupling of the transducers to the rail surface. The experimental prototype system enables the screening of 20 meters of rail from a single array position. 
 

 

 

    ULTRASONIC EVALUATION OF A BETA-C TITANIUM ALLOY

 

     Buitrago B., Irausqu��n I., Mendoza J. 

Department of Industrial Technology, Universidad Sim��n Bol��var, Sede del Litoral.

Apartado Postal 89000, Caracas 1080, Venezuela., e-mail: irausqui@usb.ve  

Abstract 

Beta-C Titanium Alloys are widely used in aerospace industry. Since these components need to be inspected for possible damage due to in-service conditions, and since ultrasound is one of the inspection techniques that can provide a more thorough evaluation, it is necessary to understand the behavior of ultrasonic waves in these media. In order to do this a set of low power transducers, with frequencies of 1.5, 5 and 10 MHz, were used to determine the wave velocity, attenuation and broadening of ultrasonic pulses traversing Ti-3Al-8V-6Cr-4Zr-4Mo plates. Also, the spectral analysis performed on the returned pulses provided the necessary information to understand the pulse broadening observed at low frequencies. In these studies the ultrasonic pulses were generated by a modern ultrasound field equipment, whereas the spectral analysis was performed by a computer connected to a fast oscilloscope that was capturing the signal returning from the plates. The experimental data is presented as well as a discussion on the effects of the interaction of longitudinal ultrasonic waves in the Ti-3Al-8V-6Cr-4Zr-4Mo alloy. From this the proper inspection frequencies was obtained.

 

    CASE DEPTH EXAMINATION BY USING VICKERS MICRO - HARDNESS TEST METHOD AT TRSC

 

P.P. Panagiotidis1, A.S. Antonatos2, G.M. Tsananas3 

1 Testing Research & Standards Centre (TRSC), CEng MIMechE MPhil PgDip MBA

2 TRSC, Manager of Metallurgical Laboratory, 3TRSC, Head of Mechanical and Metallurgical Department, 9 Leontariou Str., 15351, Pallini, Greece  

ABSTRACT 

Keywords: Carburization, Case Depth, Hardness, Microscope, Non Destructive Testing

(NDT), Vickers 

The laboratory hardness tester supported with relative software equipped with a microscope giving magnification between 10 to 40x applied the Vickers Test method on ferrous materials. The hardness difference between the core and the outer surface of a material gives the case depth. Thus it can be easily examined the case depth by measuring the diagonals of the footprint comparing it with the basic metal.  

The aim of this paper is to present our experience on examining the case depth in mechanical equipment and machinery tools of carburised parts providing information on its mechanical properties.  

Testing Research & Standards Centre (TRSC) is the testing organization of Public Power Corporation (PPC) S.A. involved with Destructive and NDT including the Metallurgical laboratory.  
 
 

 

 

    Ultrasonic guided wave tomography for the inspection of the fuel tanks floor

 

L. Mažeika, R. Kažys, R. Raišutis, R.Šliteris 

Ultrasound Institute, Kaunas University of Technology, Lithuani

ABSTRACT 

  The inspection of a fuel tank floor is a time consuming and expensive procedure, mainly due to necessity to empty and to clean the tank before an inspection. For this purpose a long range ultrasonic technique based on Lamb waves may be applied. Such an approach is used for inspection of pipes and can cover the distances up 100m. However, the storage tanks are much more complicated structures from the point of view of ultrasonic inspection due to presence of multiple lap joint welds. Differently from pipes, the tank floor should be inspected and defects detected in 2D plane. The objective of the research presented is investigation of the possibility to detect defects in a storage tank floor without emptying and cleaning it.

  The previous investigations have demonstrated that the s0 mode of Lamb waves, generated at the 50kHz frequency, enables through transmission measurements of the floor of small and medium size storage tanks with diameters 5-30m. The propagation of the s0 mode of Lamb wave in a steel plate and its interaction with non-uniformities, such as artificial and corrosion defects were investigated. It was shown that the most promising approach for detection of corroded areas in a tank floor should be based on the through transmission tomography of Lamb waves. The inspection technique based on such an approach have been developed and tested experimentally.

  The main task of the second stage of investigation was to determine accuracy limits and to optimize necessary parameters of the measurement, minimizing the number of measurements which should be performed on a tank in situ. To achieve this task the scaled physical model of a tank was developed. The measurements were performed at properly scaled higher frequencies. The adequacy of measurement conditions have been verified using modelling and experimental investigations. The experiments carried out on the scaled model and the developed signal and data processing procedures enable to visualise dynamics of ultrasonic fields over the plate and determine the position of various defects. The signals acquired during experiments have demonstrated a good agreement with the numerical simulation. It was shown that the transmission tomography based on the measurement of the Lamb waves, propagating in a tank floor, enables to obtain a spatial distribution of attenuation of Lamb waves in a tank floor, what corresponds to the corroded areas of the floor. The accuracy and the possibilities of the developed technique are demonstrated using the results of the experiments on the scaled model of the tank and the tank in situ.

 

 

    An overview of the predictive maintenance applications of Airborne Ultrasound testing

 

Joseph M. Buckley 

Sonatest Ltd, Milton Keynes England 

ABSTRACT 

Detection of Low Frequency (around 40kHz) Ultrasound is a powerful method for maintenance inspection of plant and machinery. Many failure conditions give early indication by the production of ultrasound. These include pressure leaks, electrical discharge and deterioration of bearings and other machinery. 

Leakage of compressed air has become a particular issue recently with the promotion of energy / CO2 emission reduction initiatives – most estimates suggest that in excess of 5% of industrial energy use represents wasted compressed air. 

This talk will briefly discuss the operating principles and typical equipment, and give detailed examples of industrial, transport, military and aerospace applications.

 

 

    Long Range Ultrasonic Technique for Rail Inspection

 

Krasimir Staykov, Damyan Ganchev, Svetoslav Kutzarov, Bogomil Yochev 

ABSTRACT 

Application of guided waves for rail inspection in railroad industry is considered in the paper. NDT evaluation of rails using high frequency ultrasound (US) is relatively good developed and used in practice. Basic disadvantage of this technique is connected with the attenuation of ultrasound in the welded zone due to the microstructure of the alumino-thermic weld. Additionally, the working distance of US waves propagation is short and time of inspection is relatively long.

In the paper presented a low frequency US approach is considered. It is shown that operating frequency should be less than 100 kHz. Advantage of these waves is that at such frequencies material attenuation due to grain boundary scattering is very low and weld material can be easily penetrated and tested. US propagates long distances without significant attenuation hence a long range technology (LRT) is used.

The complications of using LRT are connected with the special shape and dimensions of rail. There a number of guided wave modes that can exist in such complex structures. All of them are propagating at different, frequency dependent, velocities. After mathematical and experimental considerations are taken into account, the optimum frequency for the given rail, is estimated to be around 70 kHz.

Dispersion curves and mode shapes for guided waves in rails were calculated using finite element technique. Novel transducers were designed which produce in-plane displacements. For damping of the transducers a specially designed backing material composite was used in order to reduce the ringing effect of the piezo element at low frequencies. Experiments were conducted using a single transducer and array of four transducers. Different materials were evaluated for dry-coupling of the transducers to the rail surface. The experimental prototype system enables the screening of 20 meters of rail from a single array position. 
 

 

 

    NDT CARRIED OUT IN POWER PLANTS BY TRSC

 

A.S. Antonatos1, P.P. Panagiotidis2, G.M. Tsananas3  

1 Testing Research & Standards Centre (TRSC), Head of Metallurgical Laboratory

2 TRSC, CEng MIMechE MPhil PgDip MBA, 3TRSC, Head of Mechanical and Metallurgical Section, 9 Leontariou St., 15351, Pallini, Greece  

ABSTRACT  

Keywords: Non Destructive Testing (NDT), Power plants  

Public Power Corporation S.A. is the main electric power producer, transfer carrier, distributor and trader of Greece. Testing Research & Standards Centre (TRSC) is the testing organization of (PPC) S.A. involved with Destructive and NDT. The Mechanical and Metallurgical Section is involved with NDT by means of the Metallurgical laboratory and the Applied Physics laboratory. Finally the Destructive tests executed by the laboratory of strength of materials.

The PPC SA operational duty of the Quality Assurance System manages Non Destructive Testing of materials and welds playing an important role in controlling critical areas in materials, equipment, welding and workmanship for more than 2 decades in power plants.

All the above tests are carried out by qualified engineers and technicians which are ASNT and PCN EN 473 level II and III certificate holders approved by International NDT examination centres.  

The aim of this paper is to present our experience on inspecting the power plants equipment and machinery tools providing information derived from the occurred flows of discontinuities.  

 

 
 
 
 
 
 
 

 

SESSION 7

CERTIFICATION AND ACOUSTIC EMISSION  

    Progress Report on the development of EFNDT Guidelines for an Overall NDT Quality Management System

 

JM Farley1, JR Thompson2

1President of EFNDT 
2Chairman of EFNDT WG1

    Abstract

 

The EFNDT Board has recently initiated work on a new Strategic Plan. Under Action Plan 3, ��Overall NDT Quality System��, it was decided to prepare a Guidelines Document on the European systems for NDT Quality, with the objective of developing a better understanding by users and purchasers of NDT services of the roles of the various measures to ensure quality of NDT, including in-fabrication and in-service inspection.  

The Task Group responsible has  invited acknowledged experts to contribute one or more sections to the document, and a considerable amount of the initial drafting work is complete.  

This presentation will summarise the content of the draft guideline, highlight sectors of our industry that may benefit most from the work, and indicate the likely date when the final document will be published on the EFNDT website as a reference document. 

 

    How to merge EN 473 certification and EN 4179/NAS410 qualification in Austria

 

Gerhard Aufricht1, Roman Wottle2 

Austrian Society for NDT, Wien, Österreich

National Aerospace NDT Board, Wien, Österreich 

Abstract 

The Austrian Society for NDT (ÖGfZP) supervises examinations for the NDT personnel as an accredited, independent certifying body (CB) following EN 473 and as outside agency for  
EN 4179/NAS 410, recognized by the National Aerospace NDT Board (NANDTB Austria). 

ÖGfZP has contracts with 4 established training centres and with 3 recognized examination centres. 

EN 473 certification started with June 1993. Until the end of 2006 more than 6000 certificate-holders were supervised.     

December 2004 the ÖGfZP sector-committee ��Raum- und Luftfahrt�� offered a platform, on which the members of the Austrian Aviation Industry and one observer from the National Aviation Authority (NAA; Austro Control) founded the National Aerospace NDT Board (NANDTB- Austria).    

The NANDTB Austria was acknowledged by NAA with May 19, 2005 as a Committee of the Austrian society for Non-destructive Testing. 

NAA accepted the following statement of NANDTB Austria: 

(1) Operators which are already qualified and certified to EN 473 with a minimum of 3 years NDT    
      experience are eligible for Grandfathers Right.

(2) EN 473 Level 3 operators with a minimum of 3 years NDT experience, but without level 2  
      certification may receive a certificate (not qualified to conduct NDT for acceptance of parts) after  
      a 2 days differential course with specific examination.

(3) EN 473 Level 2 operator with a minimum of 3 years NDT experience need additional differential  
      training course for special aerospace NDT techniques and materials with specific examination  
      including general and specific questions and practical examination. 

There are two lines to receive Level 1 and 2 EN 4179/NAS 410 qualifications.

 

(1) The candidate visits one of the a. m. ÖGfZP contractors as an outside agency, for an  
      EN 4179/NAS 410 course and examination under ÖGfZP supervision.

(2) The candidate visits one of the a.m. ÖGfZP contractors for EN 473 training and examination. In  
      addition he completes differential training course for special aerospace NDT techniques and  
      materials with specific theoretical and practical examination. 

This scheme offers a cost-effective, norm-concurring qualification/certification merging for  
EN 4179/NAS 410 NDT examiners in small countries. 

 

 

    Quality assessment of a laser cut based on captured acoustic emission signals

 

Grum Janez, Tomaz Kek 

    Abstract 

    The paper presents results of an analysis of AE measurement in laser cutting of DC04 steel plate. Laser cutting was evaluated on the basis of monitoring the acoustic emission in the course of cutting by means of a PZT sensor. It was found that that the cutting oxygen gas flow was the primary source of AE in laser cutting. The incidence of the supersonic gas flow in the cutting front is demonstrated as continuous AE signals. The AE signals measured immediately after laser cutting indicate the events in the remelted and heat-affected zones of the laser cut. It was proved that the cutting conditions exerted a significant influence on the amplitude and the square integral of AE signals during laser cutting and immediately after cutting. It was found that there was a relation between the AE signals measured and a dross occurring at the laser-cut edge. The presence of the dross is an important indicator of low quality of the laser cut. This finding was successfully applied to the optimisation of the laser-cutting process in relation to the cutting conditions chosen. 

     

     

      classification of ae signals from composite materials based on parameter-less self organized mapping

     

    Georgios Kalogiannakis1,2 and Danny Van Hemelrijck2 

    1Lab Acoustics & Thermal Physics, Dept.Physics & Astronomy, Katholieke Universiteit Leuven, Belgium

    2Dept. Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Belgium 

    ABSTRACT 

    Composite matetials are characterized by different types of failure mechanisms which are typically associated with matrix cracking, fiber-matrix debonding and fiber breakage. These three mechanisms result in a different AE signature, which can be often recognised with naked eye. In certain cases it is necessary to classify and map the damage types so as to be able to evaluate the accumulated damage and remaining strength of the material. In this framework, neural networks are widely used for damage characterization of composite materials from the resulting AE activity during loading. The neural networks are trained with typical acoustic emission signals originating from the structure in operation and then are used for clustering and mapping the incoming signals during the lifetime of a construction. The typical approach involves recording waveform features like the amplitude, duration, energy and average frequency and try to associate them with the damage source. Nevertheless, very often, it is very hard to draw definite conclusions based on these features.

      In this study, we have used a new type of an unsupervised neural network which is called parameter-less self organized mapping. It is based on Kohonen neural networks but it is not bound to the naturally subjective learning rate, neighborhood function and their annealing with the training progress. Moreover, for the training of the NN, we have used the wavelet decomposed AE signals. Wavelet analysis is perfectly suitable for transient signals like AE because it contains both time and frequency information. Wavelet coefficients can be therefore used much more efficiently for the discrimination of AE signals originating from different damage sources. 

    References 

    1. Ganq Qi, Wavelet-based characterization of composite materials. NDT&E International 33 (2000) 133-144
    2. Mickael Johnson, Classification of AE transients based on numerical simulations of composites laminates, NDT&E International 36 (2003) 319-329
    3. Qing-Qing Ni, Masaharu Iwamoto, Wavelet transform of acoustic emission signals in failure of models composites, Engineering Fracture Mechanics 69 (2002) 717-728.
    4. T. Kohonen, Self-organised network. Proc. IEEE 1990;(43):59-69
    5. T. Kohonen, Self-organisation and associative memory. Springer, 1988
    6. E. Berglund, J.Sitte. The Parameter-Less SOM algorithm. 8th Australian and New Zealand Intelligent Information System Conference (ANZIIS ��03), Sydney, Australia, December 2003
    7. T.P.Philippidis, V.N. Nikolaidis, A.A. Anastassopoulos, Damage characterization of carbon/carbon laminates using neural network techniques on AE signals. NDT&E International, 31(5)(1998):329-340

     

     

      The application of Quality Assurance in NDT Measurements

     

    Dr. Konstantinos Krallis1, Prof. Dr.-Ing. Nikolaos G. Orfanoudakis2 
     

    1Heron Consultants Engineers, 107 H. Trioupi street, GR-11473  Athens GREECE, E-Mail: heron@tee.gr 

2Corresponding Author, Laboratory for Steam Boilers, Turbines & Thermal Plants, TEI-Chalkis,

GR-34400 Psachna Evia, GREECE. E-mail: norfan@teihal.gr

 

ABSTRACT

 

A major task in the industry is the application of NDT methods during the inspection of various pressure equipment (steam boilers, vessels, LPG tanks etc.) For safety reasons according to current EU Directives (PED, simple pressure vessels, TPED) and National Laws all these pressure equipment must be inspected and certified during construction and, of course, subjected to periodic inspections during operation. 

This paper contributes in the field of application of Quality Assurance during various NDT inspections as well as quality plans in such work in order to comply with certain directives and laws, thus contributing in increasing the level of services provided in the industry. The paper describes also practical problems in application of quality plans during NDT inspection of various types of pressure equipment during initial construction as well as during periodic inspection in order to comply to certain standards.

 

    Determination of Uncertainty in Calibration of Acoustic Emission Sensors

 

Keprt, J. - Beneš, P. 

ABSTRACT 

The paper reviews the background, the methodology and the standardization of the primary calibration of acoustic emission sensors. There are discussed the aims and the purpose of the primary calibration. Two basic calibration methods, which were practically realized on our test stand, are closely described and explained. It is the method of reciprocity calibration according to NDIS 2109-91 and the step function calibration according to ASTM 1106.

The reciprocity method makes use of three reversible sensors. Each time must be measured three measurements. One of the sensors works as a transmitter and the others as receivers. The absolute frequency characteristic is calculated from measured data and known transmission function of the test block. Matrix channel switch was developed to automate of the whole process. It allows to increase count of measurement and to decrease the possibility of error made by change of cables.

The step function method of the calibration takes advantage of the knowledge of time behaviour of the displacement of the surface of the test block during the step release of force point wise acting on the surface of the test block. Requested frequency characteristic corresponds to a ratio of image of the output voltage from the sensor and the calculated surface displacement in the frequency area. For the realization of step function calibration the holding metal construction was manufactured and suitable capillary had to be obtained. The construction holds the capillary breaker. Laser interefometer Polytec OFV-5000 with optical head OFV-505 and computing module DD-300 for AE was used for validation of shape of signal generated by capillary break.

As a transfer medium for wave propagation a large steel block was used. For controlling of the whole experiment PC was used. Software was programmed in LabVIEW 8.0 and controls measurement by all of the methods.

The comparison of the results of the both method is presented. Uncertainty of measurement by reciprocity calibration is determined and presented in the paper. Parasitic effect and consequential restriction of each method are presented. Also the main problems, that were solved and have to be solved, are presented in the part of the practise realization description. 

 

 
 
 
 
 
 
 
 

 

SESSION 8

ANALYTICAL METHODS & NDT -1  

    A study of the spectral behavior of Laser-generated Lamb waves using Wavelet transforms

 

T.Pramila*, Rashmi Shukla   and V.Raghuram1

 

Department of Physics, Christ Church College

1Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India

*Corresponding author, Email address: pramilatabeti@yahoo.co.uk 

Abstract 

Keywords: Lamb waves, Laser Generation, Frequency analysis 

This paper deals with the study of the spectral components of Lamb waves generated in thin aluminium plate using pulsed Nd-YAG laser and detected using a He-Ne Laser Heterodyne interferometer.  Laser generation of Lamb waves leads to simultaneous generation of various frequency component as well as multiple Lamb wave modes. The Lamb wave signals are successfully and comprehensively analyzed using Wavelet transform technique. The velocities of various frequencies present in the Lamb wave   signal are calculated and the experimental dispersion curve is plotted. The behavior of various frequency components with respect to reflection from plate ends is explained satisfactorily. 
 

 

 

    Frequency analysis of Laser-generated pressure waves using wavelet transforms

 

T.Pramila, Anita Shukal  and  V.Raghuram1*

 

    Department of Physics, Christ Church College

1Department of Mechanical Engineering, Indian Institute of Technology Kanpur, Kanpur, India

*Corresponding author: Email: vraghu@iitk.ac.in 

ABSTRACT 

Keywords: Laser generation, pressure waves, frequency spectrum 

This paper deals with the analysis of the pressure wave signals generated in an aluminium stepped sample. The ultra sonic signals are generated using pulsed Nd-YAG laser and detected using a He-Ne Heterodyne interferometer.  The  pressure wave signals at constant laser power are recorded at various directions with respect to source laser direction and the   intensity of various frequency components present in these pressure wave signals are estimated with the help of coefficient lines in theirs wavelet transforms. The variation of the intensity of individual frequency components with detection direction and the intensity variation with signal frequency at a given detection direction are studied and the results are presented. 
 
 

 

 

    NONDESTRUCTIVE THERMAL CHARACTERISATION OF THE LAYERS DETACHMENT IN THE ROADWAYS

 

    A. Elballouti, S. Belattar 

    Laboratory of Electronics, Instrumentation and processing of the signal

    Faculty of Sciences, 24000 El Jadida, Morocco

    Corresponding author: E-Mail: belattars@hotmail.com 

    ABSTRACT 

    In this work, we present numerical simulations, in 3 dimensions, it concerns the studying of the aptitude of the thermal nondestructive testing to detect the detachment of layers in the various roadways structures: flexible, semi-rigid and rigid. We will study the position and the size influence of detachment type defect, on the level of the various layers on the simulated thermographical image on the surface. For that, we will consider three parallelepipedic roadways structures, of same dimensions; the one first is of flexible type, the second semi-rigid one and the third rigid one. These structures are excited by a heat flux on the surface, the opposite face being maintained at a constant temperature and other surfaces are thermically isolated. Detachment between two layers of the roadway is materialized by a blade of air. When the steady mode is established, we will take and study the thermgraphical image on the surface. This study is made using computation numerical software, based on the finite element method.

     

     

      Crack Diagnosis in Beams Using Propagated Waves and HHT Transform

     

    M. H. Soorgee1, A. Yousefi-Koma2 

    1Graduate Student, Advanced Dynamic and Control Systems Lab, School of Mechanical Engineering,

    University of Tehran, Tehran, Iran, mhsoorgee@yahoo.com

    2Assistant Professor, Advanced Dynamic and Control Systems Lab, School of Mechanical Engineering,

    University of Tehran,Tehran,Iran, aykoma@ut.ac.ir 

    Abstract 

    Keywords: Piezoelectric, Hilbert Huang Transform, Wavelet, Health monitoring 

    This paper is a numerical simulation and verification of health monitoring of beam structures using propagating waves. The goal is to detect the location of a linear crack in a beam using piezoelectric sensor based on the time-of-flight of propagating waves. The actuation signal is an impact inflicted on a predefined location on the beam. The commercial finite element code (ABAQUS) has been employed to model a beam with piezoelectric sensor and a tiny groove representing the crack. After a transient dynamic analysis, the sensor voltage has been acquired. Using Hilbert Huang Transform (HHT) method, from the time-energy spectrum of sensor response, the arrival time of the incident and reflected waves to the sensor has been computed. Based on the time-of-flight of the propagated waves, the wave speed was obtained by dividing the propagated distance by the arrival time of the incident wave. Having computed the wave speed, the location of the crack was detected by multiplying the wave speed by the time span between the arrival time of the incident and reflected waves to the sensor. A wavelet analysis has also been employed to validate HHT results. There was good compatibility between numerical simulation and the experimental work done by Tua et al (2003).

     

     

      Advanced Neural–Fuzzy and image PROCESSING TECHNIQUES in the AUTOMATIC DETECTION and interpretation of weld defects using ultrasonic Time-Of-Flight-Diffraction

     

    C��Shekhar N. Shitole, O. Zahran and W. Al-Nuaimy 

    Department of Electrical Engineering & Electronics, University of Liverpool,

    Brownlow Hill, Liverpool L69 3GJ, United Kingdom

    Tel: +44 151 794 4580, Fax: +44 151 794 4540

    Email: cshekhar@liverpool.ac.uk 

    ABSTRACT 

    Ultrasonic Time-of-Flight-Diffraction (TOFD) technique has gained significant reputation in the non-destructive testing due to its ability in the accurate detection, sizing and positioning of weld flaws in steel structures. This technique is further endorsed by its reliability, portability and cost-effectiveness in the automatic scanning and data acquisition. Although automatic data acquisition systems combined with robotic scanning being effective depends on the skills, experience, alertness and consistency of the trained operator. Thus, interpretation results suffer errors especially dealing with the large volume of data. The three key issues, due to which fully automatic TOFD interpretation system for the weld flaws, could not be achieved are classification of defects due lack of unique defect signatures in a TOFD data, inconsistent detection of the near surface weld flaws and lack of standard guidelines for the data interpretation. However, a fully comprehensive automatic detection, sizing, positioning and classification TOFD system can be achieved using advanced image processing, signal processing and artificial intelligence techniques, thus reducing time, cost and errors in the interpretation of weld flaws in the steel structures. 

    This paper presents number of advanced methods used for the automatic detection and classification of weld defects in TOFD data. The mode converted wave technique is also investigated in order to detect the near surface flaws. The weld flaw types includes planar, volumetric, threadlike and point flaws, which are subdivided into different subcategories. Advanced signal and image processing techniques are used for the segmentation, classification and characterisation of weld defect types.  In the classification stage three different classification techniques are employed and compared – artificial neural network-based classifier, fuzzy logic-based classifier and a hybrid neural-fuzzy classifier. A neural classifier can learn from data, but the output does not lend itself naturally to interpretation. A fuzzy classifier on the other hand consists of interpretable linguistic rules, but they cannot learn. A neuro-fuzzy classifier is based on a 3-layer feed-forward neural network. The first layer is for input variables, the middle (hidden) layer is for fuzzy rules and the third layer is for output variables. Therefore, using a hybrid classifier is an advanced artificial intelligence approach which has advantages of both neural networks and fuzzy logic. The developed neural-fuzzy classifier exhibits high levels of accuracy, consistency and reliability, with acceptably low computational time and is a promising new development in the field of fully automatic weld inspection.  
     

     

      A Stochastic NDT Method for Damage Identification and Predictive Modeling for Mechanical Properties Degradation due to notch existance in Composite Materials

     

    ABSTRACT 

    K.E. Giannadakis1, P.I. Rokas1, P.G. Michailides2, S.D. Fasois2 and G.C. Papanicolaou1 

    1Composite Materials Group, Mechanical Engineering and Aeronautics Department, University of Patras, Greece

    2Stochastic mechanical systems and automation, Mechanical Engineering and Aeronautics Department, University of Patras, Greece 

    Unlike conventional metallic materials, composite structures fail under different failure modes. The initiation of the damage does not mean that the structure cannot carry any additional load. The residual load bearing capability of the composite structure from the onset of material failure or initiation of damage to final failure can be quite significant. Therefore, it is important to understand the damage initiation and progression in composite structures subjected to combined loading conditions.A cumulative procedure of damage generation is observed which, in turn, results in material property degradation.  

    In the present paper, a vibrational NDT method along with Stochastic Pooled modelling was used for the damage identification due to the existence of edge notches in certain composite materials. Experiments were executed in a series of GFRP composites. Next, the Residual Properties Model (RPM) was applied in order to predict the mechanical properties degradation with the notch length. Finally, theoretical predictions were compared with respective experimental findings and respective damages were correlated with predicted material property values.

     

     
     
     
     
     
     
     
     

     

    SESSION 9

    ANALYTICAL METHODS & NDT -2  

     

      NUMERICAL SIMULATION ANALYSIS OF THE SENSING CAPABILITIES FOR EMBEDDED METALLIC GRID, APPLIED TO COMPOSITE PATCH REPAIR

     

    G.J.Tsamasphyros, G.Kanderakis, A.Christopoulos  

    The National Technical University of Athens,

    Faculty of Applied Sciences, Dept. of Mechanics-Lab of Strength Materials, Zografou Campus,  Theocaris Bld.,GR-015773, Athens, Greece 

    ABSTRACT 

    Keywords : Composite Patch Repair, Structural Health Monitoring, Induction Heating 

    The development of fibers and adhesive systems (cohesive) with high durability, led the last years to the creation of a new repair method of metallic structures by the use of reinforcing patches from composite materials. This technique is reported in the international bibliography as "Composite patch repair" and provides very important advantages compared to the conventional methods of repairs. On the other hand the technology of induction heating constitutes an innovative approach to achieve supply of energy for the curing of resins or for the manufacturing of composite materials.  Induction heating, takes place in the ferromagnetic materials, when these are submitted in periodically varying magnetic field. As a result Eddy Currents are induced in the material,  producing heat  (Joule phenomenon). In the case of curing resins, a ferromagnetic material must be imported inside, to produce the required heat. This may be achieved by importing a metallic grid in the resin. Moreover this metallic grid which remains inside the resin after the curing may serve as sensor by analyzing it��s electrostatic properties, thus providing useful information about the structural integrity of the area (potential increase of the crack below a bonded composite repair).  Every change in grid��s total resistance is translated as deformation. As it was proved via numerical simulations, by the use of a Neural Network it is possible to calculate  plate��s  crack length and the size of the deforming  load, with exceptional precision, receiving only four measurements of intensity I of electric current . 

     

     

     
     

      Bacterial Magnetic Particles for Potential Applications in Nanoscale NDT&E

     

    E. Siores, K. Meramveliotaki and A. Lamb 

    Centre for Materials Research and Innovation, Bolton University, Bolton, BL3 5AB, UK 

    Abstract 

    Current NDT techniques are capable of identifying sub millimetre defects in structural materials. Nanoscale NDT however, necessitates development of new techniques for identifying and sizing surface and more importantly subsurface imperfections. The reliability of micro and especially nano scale components heavily depends on such new developments. This paper presents a first attempt to explore the potential of bactrerial magnetic cells for applications in NDT&E. Such bacteria cells having dimensions of a few microns can form single crystals of iron magnetite encapsulated in a magnetosome membrane. Crystals are structured in a long chain arrangement and polarised in the north / south direction, thus allowing the bacteria microorganisms to behave as magnets. Since their discovery in the 70s, different magnetotactic bacteria morphologies producing various magnetic minerals have been observed and a few have been successfully cultured. At present, emphasis is placed on understanding the mechanism of magnetic synthesis and associated crystalline structure behaviour, while a few applications are beginning to emerge. Such applications include magnetic storage devices, cell separation and magnetic resonance imaging (MRI). A review of available biomagnetic species is provided together with their taxonomy properties. Their behaviour in different environmental conditions is also described. Harnessing their intrinsic magnetic properties for potential applications in nanoscale NDT&E is explained and the benefits and limitations are outlined.   
     

     

      The Influence of Coupled Thermal Fields on the behavior of Cracked Bodies

     

    D. I. Bardzokas, P. N. Lalou 

    School of Applied Mathematics & Physical Sciences, National Technical University of Athens

    9, Heroon Polytechniou str, Zografou, GR 157 80, Athens, Greece 

    ABSTRACT 

    The properties and the quality of materials are determined most of the times under the coupled action of mechanical and physical fields. A most common characteristic in the structure of materials is the appearance of discontinuities such as cracks holes and several types of inclusions that ultimately determine their behaviour. Hence the systematic study of the interplay between the applied coupled fields and the discontinuities is of great importance both in material science and engineering.

    The purpose of the paper is to investigate the action of thermal fields on materials in the presence of two coupled sources: (a) a heat flow coming from infinity, and (b) a heat dipole.

    We derive the singular integral equations and we study the behavior of the stress-intensity factors with respect to the thermal factor. 

     

      Statistical Damage Diagnosis in Smart Systems Using Non-Contact Magnetoelastic MetGlass Sensors and Stochastic Modeling of Input/Output Data

     

    Dimitrios G. Dimogianopoulos1, Dionysios E. Mouzakis2 and Dimitrios Kouzoudis3 

    1Department of Mechanical and Aeronautical Engineering, University of Patras, Greece, RION CAMPUS, GR 26504

    2Department of Materials Science, University of Patras, Greece, RION CAMPUS, GR 26504

    3Department of Engineering Sciences, University of Patras, Greece, RION CAMPUS, GR 26504

    Abstract

     

    The current study aims at using promising magnetoelastic (ME) metallic glass (MetGlass) stripes to evaluate the mechanical response of vibrating polymer slabs and statistically diagnose their health state by means of a contact-free and non-destructive approach. The main property of the ME materials is that their magnetization depends on their mechanical properties and thus remote magnetic measurements can reveal information about their internal state [1]. Such magnetic measurements are contact-free and may, hence, be obtained remotely and non-destructively. In the current case, the ME glasses are used as embedded elements in polymer slabs, accordingly forming smart systems, whose mechanical behavior and current health state is assessed and occurring damage is diagnosed (that is, detected and evaluated).

    The experiment procedure involves the preparation of polymer epoxy resin slabs for series of tests, by attaching a stripe of ME MetGlass alloy to their surface. These smart systems are tested in both ��healthy�� and ��faulty�� states (that is, state involving damage of various levels). This artificial damage is inflicted on the slabs by sequentially drilling, at each test, a number of holes of given diameter. The slabs (in both healthy and faulty states) are dynamically loaded under various frequencies in time–related oscillation amplitudes in a TA Instruments Dynamic Mechanical Analyzer [1].

    The excitation (strain) and output (EMF voltage) signal data for both healthy and faulty system test cases are remotely collected (contact-free) by means of a detection coil located over the sample. The underlying dependencies, between the excitation and output signal data, characterize the structural properties of the smart system in its current health state [2]. These dependencies may be modeled via suitably selected stochastic representations [3], which (being of stochastic nature) are able to account for noise and other disturbance-related uncertainties in the measured data. The key idea of the proposed diagnosis approach relies on the typical system behavior in healthy state being accurately modeled, by using data from healthy test cases to identify the corresponding stochastic representation. Ultimately, diagnosis of potential damage for a given system in unknown health state is reliably achieved by collecting its test-resulting data, and statistically comparing its behavior with that of the benchmark healthy system, modeled via the previously identified stochastic representations.

    References:

    Kouzoudis D. and Mouzakis D.E., A 2826 Metglass Ribbon as A Strain Sensor for Remote and Dynamic Mechanical Measurements, Sensors and Actuators A, v. 127, pp. 355-359, 2006.

    Dimogianopoulos D.G, Hios J.D. and Fassois S.D., Fault Detection and Isolation in Aircraft Systems Using Stochastic Nonlinear Modeling of Flight Data Dependencies, in 14th Mediter-ranean Conference on Control Automation, MED 2006, Ancona, Italy, 2006.

    Fassois S.D. and Sakellariou J.S., Time Series Methods for Fault Detection and Identification in Vibrating Structures, Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences, vol. 365, pp. 411-448, 2007.

     

      Structural health monitoring of composite patch repairs using embedded fiber bragg grating sensors and neural network techniques

     

    G.J. Tsamasphyros , N.K. Fournarakis , K. Kalkanis, A. Christopoulos, G.N.Kanderakis 

    The National Technical University of Athens,

    Faculty of Applied Sciences, Dept. of Mechanics-Lab of Strength Materials, Zografou Campus,  Theocaris Bld.,GR-015773, Athens, Greece 

    Abstract 

    Keywords : Composite Patch Repair, Structural Health Monitoring, Fiber Bragg Grating Sensors 

       Modern developments in the space of aeronautics render explicit the need for exploitation of air structures up to their designed structural life or even further and consequently the need for adoption of maintenance techniques supporting their structural integrity in an acceptable, according to their designed criteria, manner. One of the most promising¶ techniques is the so called ��composite patch repair method��, a method capable to repair cracked metallic structures using adhesively bonded composite patches, that constitutes an effective method for re-establishment of structural integrity. ¶However, even though this method has important advantages, problems concerning the long-term behavior of the adhesive, the appearance of debonds, etc. appear and have led to the considerable delayed widespread acceptance of this method. ¶

      ¶In the present study the realization and implementation of elements of a structural health monitoring system for composite patch repairs is being performed, combining elements from the theory of structural repair mechanics, the theory of intelligent materials and structures and particularly the technology of optical sensors and neural networks.

      The study has been split in two parts.  In the first part a presentation of the experimental set up as well as the subsequent experimental results ¶are presented. Two major potential failures have been considered and studied experimentally: the repaired crack extension despite the repair and the debond of the adhesive bonding of the composite onto the metallic structure.  In the second part, the inverse problem of fault detection, qualification / quantification and life expectancies are studied using neural network techniques. Various network learning algorithms are evaluated for the corresponding failure cases and comparison results are developed. The data taken from the experimental test series (part I of the study) are used as network exemplars for training/test reasons and the corresponding deviations are calculated as well as the network performance metrics.

     

      A Methodology for Vibration-Based Non-Destructive Testing Using Wavelet and Hilbert-Huang Transforms

     

    Joanna Rizou1, Alexander F. Vakakis2

                        

    Mechanics Division, School of Applied Sciences, National Technical University of Athens, P.O. Box 640142, GR-157 10 Zografos, Athens, Greece

    Graduate Research Assistant, jrizou76@yahoo.gr

    Professor, vakakis@central.ntua.gr 

    ABSTRACT 

    Keywords: Hilbert Huang Transforms, wavelets 

    We present a new technique for structural damage detection based on vibration testing and post processing of the measured time series by combined Wavelet and Hilbert-Huang Transforms. The structure tested is a steel hollow cylinder with one edge fixed. By applying short pulse excitation, we show that the applied transforms are capable of identifying small defects. The damage detection is performed by studying the instantaneous frequencies and mode shapes of the intrinsic mode functions (IMFs) resulting from application of the HHT, and comparing these frequencies to wavelet spectra. We show experimentally that certain high-frequency IMFs are sensitive to the presence of defects, and, hence, can be used to detect the presence of damage. 
     

     

     
     
     
     
     
     
     
     

     

    SESSION 10

    EDDY CURRENTS & INDUSTRIAL APPLICATIONS

     

      The use of a SQUID for quantitative magnetic field measurements in the nanoTesla region for eddy current NDE

     

    Nikolaos POULAKIS 1 and Theodoros THEODOULIDIS 1, 2 

    1Technological Educational Institute of West Macedonia, Greece

    2University of West Macedonia, Greece 

    ABSTRACT 

          Eddy current testing traditionally relies on the detection of impedance changes of a pickup coil while this is moved across the inspected specimen. In order to detect deep flaws in conductive materials, low excitation frequencies are required to achieve a sufficient penetration depth. Since the sensitivity of normal pickup coils is proportional to the excitation frequency, standard eddy current techniques are insufficient for deep subsurface flaw detection. In such cases it is more advantageous to measure the magnetic field rather than its rate of change (coil impedance change) and hence magnetic field detectors are used such as Hall sensors, Giant Magnetoresistive sensors (GMRs) or SQUIDs. The latter is the most sensitive one, thus making it ideal for the measurement of very weak magnetic field perturbations resulting from deep lying defects. Although it requires cooling of the device to achieve superoconducting conditions, it has nevertheless gained considerable attention during the last years and much applied research is performed with the ultimate goal of its commercialization in the field of Non Destructive Evaluation.

          Within the funding programme ��Archimedes II�� for the promotion of technological research in Technological Educational Institutes, under the auspices of the Ministry of National Education and Religious Affairs of Greece, we have integrated a HTS SQUID system to a scanning unit and thus developed a complete measuring unit for experimental investigations. Initially, we address a number of issues that arose during the measurements, for example: (i) In order to measure quantitatively we had to evaluate the unique transfer function of the SQUID system (in terms of nT/V) by performing a careful calibration procedure involving a shielded chamber. (ii) In order to reduce the excessive output signal, that was saturating the lock-in amplifier��s electronics, we re-designed the excitation coil as a double-D or double- Printed Circuit Board coil. The study is then focused on the examination of deep penetration and the comparison of experimental results to theoretical ones by using existing eddy current models. Various configurations are examined including conductive plates with or without flaws in the form of cuts and slots. In general, good agreement is observed between theoretical results and experimental measurements.

          In conclusion, in this paper we perform a feasibility study regarding the use of a HTS SQUID magnetometer for quantitative measurements in eddy current NDE. The difference with other studies so far is the use of the SQUID in absolute rather than in gradiometric mode. Thus, we investigate the possibility of taking accurate measurements in ambient noise environments and in this way we demonstrate the unique features of SQUID magnetometry.

     

     

      A TRIO OF TECHNIQUES FOR EDDY CURRENT INSPECTION

      OF TUBES AND BARS

     

    Uday Godbole 

    Director, Technofour, udayg@technofour.com 

    Abstract

     

    Encircling coil eddy current testing has been employed in tube mills since early part of the last century.  This was followed, several years later, by rotating probe eddy current inspection of bars for detection of longitudinal surface flaws.  Availability of powerful computing platforms over the last decade has spurred development of a new technique for inspection of tubular products, employing eddy current arrays. 

    This paper outlines the dramatic evolution in test systems, and goes on to discuss the latest equipment exploiting each of the three techniques.  It also offers an objective evaluation of strengths and weaknesses of each test method. 

     

     

      Ultrasonic and Eddy current Examination of Railway Rolling Stock

     

    Ioannis Tsompanidis1, Vasilios Tsiakas2 

    1ELESYL OE, Athens, Greece

    2Athens Metro Operating Company S.A., Athens, Greece 

    Abstract 

    The major problems that a rail network has to face during operation of rolling stock are wheel RCFs, cracks in wheels, cracks in wheels tyres, cracks in axles, cracks axle box, wheel profile wear and cracks in bogies. If these deficiencies are not controlled at early stages that might cause huge economical problems affecting the rail network (unexpected requisition of spare parts, handling of incident and/or accidents). The early and continuous use of NDTs can save both money and human lives. Talking about ��money��, scheduling of spare parts orders as well as the early repairing of rail components may be performed before they will turn out to be scrap materials. Talking about ��human life�� by performing NDTs human lives can be saved since failure of materials can be easily predicted and evaluated under certain procedures and methods applied.  

    Since 2003 the company ELESYL O.E. performs extended NDT services within the Greek rail network market. These services are consisting of procedures and specifications�� implementation, NDT inspections and Level 3 consultations. For NDT inspections both manual and ��automatic�� systems are used. 

    The company ELESYL O.E. together with the Athens Metro Operation Company S.A. developed and implement ultrasonic and eddy current procedures for examination of rolling stock. The procedures has been developed for detection of RCF type defects along with internal wheel and tyre defects, as well axle defects, providing information of the defected position and depth, without disassembly the components from train. 

    The actual examination procedures and the statistical expected defects will be presented.

     

      Automatic eddy current data analysis

     

    Raimond Grimberg1, Adriana Savin1, Sorin Leitoiu1, Alina Bruma2, Rozina Steigmann1,

    Lalita Udpa3, Satish S.Udpa3 

    1 Nondestructive Testing Department, National Institute of Research and Development for Technical Physics,47 D. Mangeron Blvd., Iasi, 700050, ROMANIA

    2Faculty of Physics, Al.I.Cuza University,11 Carol I Blvd., Iasi, 700506 Romania

    3Department of Electrical and Computer Engineering, College of Engineering

    Michigan State University, 2120 Engineering Building, East Lansing, MI 48824 – 1226, USA 

    ABSTRACT 

          The interpretation of NDT data involves taking a decision as to whether the observed signal response is a flaw signal or noise. The simplest approach to make this decision is to choose a threshold signal level such that all signals above the level are classified as flaw signals and all signals below the level are interpreted as noises. If the signal and the noise probability density functions overlap, the data interpretation process based on threshold detection will invariably involve two types of errors which are of significance: false alarm and false acceptance.

          This problem becomes acute when data amount which must be processed is very large and the time allocated for control is small, and must appeals to automated interpretation and signal classification systems, situation frequently met at eddy-current examination of tube bundle from stream generators, heat exchangers and pressure tubes during in service inspection.

          This paper proposes the development of an automated interpretation method for the eddy-current inspection data of risk components from the nuclear-electrical power plants, based on Neyman-Pearson criterion, which, for the proposed case can be state as following: maximization of the probability of detection of the discontinuities, maintaining the probability of false alarm at least at a previous fixed level. The method is applied for two type of eddy current transducer: inner transducer with rotating magnetic field [1] and rotating probe [2].

          We present the principles of ��extract features�� of the signals selected by procedure described above and those from automatic classification based on a neural system. The data comes from eddy current examination of non-radiated pressure tubes and pipes of stream generator. The results are compared with destructive tests, obtaining a very good correlation, which validates the proposed method. 

    References:

    1. R. Grimberg, Lalita Udpa, Adriana Savin, Rozina Steigmann, S. Udpa, Inner eddy current transducer with rotating magnetic field; experimental results; application to nondestructive examination of pressure tubes in PHWR nuclear power plants, Research in Nondestructive Evaluation, Springer-Verlag New York, LLC, vol 16, issue 2, 65-78
    2. S. S. Udpa, L. Udpa, Eddy Current Nondestructive Evaluation, Wiley Encyclopedia of Electrical and Electronics Engineering, J.G. Webster Ed., vol.6, 1999, 149-163
     
     

          This paper is supported by the Romanian Ministry of Education and Research - Research of Excellence Program, Contract No.6110/2005 SINERMAT and Nucleus Program, Contract No. PN 06 - 38 01 03.

     

     

      CHARACTERIZATION OF EDDY CURRENT SIGNAL FROM QUATREFOIL TUBE SUPPORT PLATE FLOW HOLE BLOCKAGE OF STEAM GENERATOR TUBES

     

    Min-Kyoung Kim and Chang-Jae Yim 

    Korea Advanced Inspection Technology Inc.

    461-61 Jeonmin-dong, Yusong-gu, Daejeon, 305-811, Korea

    minky@kaitec.co.kr / cjyim@kaitec.co.kr 

       Over the past years, several cases of steam generator problems associated with the presence of secondary side deposits have been reported. In case of Westinghouse Model F steam generators, quatrefoil tube support plate design was expected to have better flow path avoiding deposit of particles and the possibility of tube corrosion. But as operating time increases, recent experiences of Model F steam generators reveal that water level oscillation can occur because of quatrefoil flow hole blockage, which causes degradation in the thermal performance of steam generators and necessitates quatrefoil flow path blockage monitoring.

          These oxides which block quatrefoil flow hole or form scaled deposits on tube surface are difficult to remove and require strong cleaning method such as chemical cleaning which needs a lot of time and high cost. Therefore, it would be desirable to measure and analyze the rate of blockage in various aspects to estimate the most appropriate time of secondary side cleaning.

          Technologies to measure and analyze scaled deposits on tube surface have been already developed and applied to field services, but methods to measure tube support flow hole blockage are  still underdeveloped or on trial in several ways.

          In this paper, a mock-up has been set up to characterize parameters of scaled deposit and to generate baseline data as a reference for field data analysis. Also, eddy current data have been acquired through experiment to observe eddy current signal characteristics from various shape of quatrefoil flow hole blockage, suggesting field analysis guidelines for signal calibration and evaluaton.

     

     

      Application of eddy current testing for inspecting condenser tubing in PPC fossil power plants

     

    Panagiota TSAGKARI 1 Antonios ANTONAKAKIS1 and Theodoros THEODOULIDIS 2 

    1Public Power Corporation, KDEP, Greece

    2University of West Macedonia, Department of Energy Resources, Greece 

    ABSTRACT 

          Eddy current testing is traditionally used for inspecting heat exchanger tubing in power plants. These exchangers are of the shell-tube type and eddy currents are preferred due to their great speed and accuracy in flaw characterization. Available standard procedures for such inspections are based on the technique of phase analysis and specifically on the use of ASME (Section V, Article 8, Appendix I). However, the ASME procedure is better adapted to steam generator tubing like those found in PWR nuclear power plants where the flaws originate from the outside (OD) of the tube wall and is not particularly suited to flaws emerging from the inside (ID). Such flaws are uniform thinning or pitting and they are common with fossil power plant condensers made of copper alloy tubes. In this case we have to develop specific procedures following tests of tube mock-ups taking into account the history of the particular condenser. Within the framework of collaboration between PPC/KDEP and the University of West Macedonia we have developed a procedure for the inspection of heat exchanger tubes of the main condenser units of the PPC fossil power plants. In this work we present the main issues arising during such inspections and focus on a specific condenser of the Ag. Dimitrios power plant.

          The specific tube bundles suffered from inlet corrosion which is caused by the turbulence of water entering the Admiralty Brass tubes. Countermeasures that were taken in the past by the plant maintenance involved the installment of either plastic or copper alloy (CuNiAl) inserts. The purpose of the inspection was to check the condition of these inserts and to monitor any additional corrosion that may have started meanwhile. The equipment used was quite sophisticated and allowed inspection at four simultaneous frequencies (sixteen information channels before mixing). Data was gathered on computer hard-disk and was analyzed later off-line. The area of interest where ID thinning was expected was close to tube end, tube expansion zone and also baffle plate. Thus, an additional step in the preparation of the procedure was taken apart from manufacturing similar calibration blocks. This step involved the simulation of the geometry by proprietary eddy current software and helped in understanding the effect of the various parameters prior to both the inspection and also to signal analysis. As a result of the inspection, very small corrosion was observed under some of the inserts, thus proving their adequacy in protecting the tubes. In addition, in some cases, a small but not alarming initiation of further corrosion was observed at the end of the inserts. 

     

     

      Light form of combined Ultrasonic and Eddy current Examination System for Railway Infrastructure

     

    Ioannis TSOMPANIDIS1, Panagiotis TEREZAKIS2, Panagiotis KOUZIS2, Ioannis TZANIS2, Pavlos PAPPAS2 

    1ELESYL OE, Athens, Greece

    2Athens Metro Operating Company S.A., Athens, Greece 

    Abstract 

    The major problems that a rail network has to face during operation are RCFs, cracks in the frog nose, cracks in frog body, cracks in guard rail base plates, defective welds, defects in crossing blades, corrugation and rail profile wear. If these deficiencies are not controlled at early stages that might cause huge economical problems affecting the rail network (unexpected requisition of spare parts, handling of incident and/or accidents). The early and continuous use of NDTs can save both money and human lives. Talking about ��money��, scheduling of spare parts orders as well as the early repairing of rail components may be performed before they will turn out to be scrap materials. Talking about ��human life�� by performing NDTs human lives can be saved since failure of materials can be easily predicted and evaluated under certain procedures and methods applied.  

    Since 2003 the company ELESYL O.E. performs extended NDT services within the Greek rail network market. These services are consisting of procedures and specifications�� implementation, NDT inspections and Level 3 consultations. For NDT inspections both manual and ��automatic�� systems are used. 

    The company ELESYL O.E. together with the Athens Metro Operation Company S.A. developed a rather light form of combined ultrasonic and eddy current examination system. The system has been developed for detection of RCF (head checks) type defects along with internal rail defects, providing information of the defected position and depth. The previously mentioned system is adopted and implemented since August 2006. 

    The actual system and results will be presented.

     

     
     
     
     
     
     
     
     

     

    SESSION 11

    CIVIL ENGINEERING APPLICATIONS  
    INFLUENCE OF STEEL REINFORCEMENT ON ULTRASONIC PULSES VELOCITY

     

    Raffaele Pucinotti1, Luana Hinterholz2 , Alessandro De Lia1, Rita A. De Lorenzo3 

    1Department of Mechanics and Materials, Mediterranean University of Reggio Calabria, Italy

    2Heritage Architect in Reggio Calabria, Italy

    3Architect inReggio Calabria, Italy 

    ABSTRACT 

    In this paper the influence of the steel bars presents in the concrete on the propagation velocity of the ultrasonic waves is reported. In particular a series of 5 specimens of concrete were considered and a series of non-destructive tests were conducted with the objective to assess the influence of both longitudinal and transversal steel reinforcements on velocity measurements.

    The experiment tests has been conducted on an simple concrete 300x300x500-mm specimen and on 4 300x300x500-mm reinforced concrete specimens unlike each other for the longitudinal and transversal spaces of reinforcements.

    Results shows that the steel reinforcements modifies, in meaningful way, the course of the ultrasonic waves and is velocity too. In fact, it is common knowledge, that the pulse velocity measured in reinforced concrete in the vicinity of reinforcing bars is usually higher than in plain concrete of the same composition. This is because the pulse velocity in steel may be up to twice the velocity in plain concrete and, under certain conditions, the first pulse to arrive at the receiving transducer travels partly in concrete and partly in steel. The apparent increase in pulse velocity depends upon the proximity of the measurements to the reinforcing bar, the diameter and number of bars and their orientation with respect to the propagation path.

    The applications have point out the importance of the corrected assessment of the position of the longitudinal and transversal steel bars in the elements investigates. That in order to avoid to carry out measures in the vicinity of reinforcing bars. Finally a series of comments are point out, basing of BS 1881-203/86, on the effect of reinforcing bars.  
     
     

    References:

    BS 1881-2003-1986 – TESTING CONCRETE – Recommendations for measurement of velocity of ultrasonic pulses velocity.

     

      WINDSOR PROBE TESTS: ASSESSMENT OF EQUIVALENT AGGREGATE HARDNESS BY NEURO-FAZZY TECHNIQUES

     

    Raffaele Pucinotti1, Mario Versaci2  

    1Department of Mechanics and Materials, Mediterranean University of Reggio Calabria, Italy

    2Department of Infornatics, Mathematics, Electronics and Transportations Mediterranean University of Reggio Calabria, Italy 

    ABSTRACT

     

        KeyWords: Non-destructive investigations, concrete, Windsor Probe System, Neuro-Fuzzy Systems
     

    In this paper a series of non-destructive and destructive laboratory tests has been performed with the purpose to investigate the influence of the aggregate hardness on the result of Windsor probe tests.

    In fact, the tables relating the exposed length of the probe with the compressive strength of concrete dependently of the hardness of the aggregate as measured by the Mohs��scale of hardness.

    In the practice, the more probable values of mechanicals property are determined by choice of the appropriate aggregates hardness.  

    A series of specimens by aggregates having various Mohs hardness (inert of fluvial origin) and by aggregate with only a class of Mohs hardness (crushed aggregate) has been prepared.

    During the concrete casting a series of cubical specimens has been prepared. The comparison between penetration tests  and cores strength are carried out.

    The tables relating the exposed length of the probe with the compressive strength of concrete dependently of the hardness of the aggregate as measured by the Mohs��scale of hardness.

    The more probable values of mechanicals property are determined by choice of the appropriate hardness of the aggregate.

    The more suitable choice of the Mohs hardness is carry out by Neuro-Fuzzy techniques.

    Fuzzy Surfaces techniques have been exploited in order to reduce the computational complexity and to select the input set of our system. 

     

     

      THE USE OF MULTIPLE COMBINED NON DESTRUCTIVE TESTING IN THE CONCRETE STRENGHT ASSESSENT:

      APPLICATIONS ON LABORATORY SPECIMENS

     

    Raffaele Pucinotti 

    Dipartimento di Meccanica e Materiali, Universit�� ��Mediterranea�� di Reggio Calabria,

    loc. Feo di Vito – 89060 Reggio Calabria, Italy.

    raffaele.pucinotti@unirc.it; fax. +390965875201

     

    ABSTRACT

     

        Key Words:  Non-destructive investigations, concrete, Windsor Probe System, SonReb Methods, Combined Methods 

        In this paper a series of non-destructive tests has been performed with the purpose to investigate on the mechanical properties of the concrete employed in the civil buildings.

        A series of specimens were prepared in order to correlate the ��in situ�� concrete strengths obtained by multiple combinated non-destructive methods with the cubical and cylindrical strength obtained by destructive methods. The multiple combined methods (SonReb Methods + Windsor Probe Tests) were used to quality control and strength estimation of the concrete.

        In particular, a series of specimens by aggregates having various Mohs��Hardness (inert of fluvial origin) and by aggregate with only a class of Mohs��Hardness (crushed aggregate) has been prepared. During the concrete casting a series of cubical specimens has been prepared. The comparison among non-destructive tests, cubical strength and cores strength are carried out.

        With reference to Windsor Probe Systems, the study has evidenced that, when a concrete by aggregate of fluvial origin is employed, the hardness of the aggregate assume a important role in the correct evaluation of strength.

        Besides, the study has evidenced: (i) great variations of the mechanics property of the materials; (ii) the better affidability of the combined method; (iii) the necessity to calibrate the resistance obtained by the non destructive methods with the strength of cylindrical specimens (cores) extract from some structural elements in the proximities of the non-destructive tests; (iv) for all the methods employed, the sensivity decreases with decreasing of actual strength.

         

          An Experimental Research on Three-Dimensional Waves in a Concrete Panel

         

        Helsin Wang1 and Richard J. Finno2 

          ABSTRACT 

          The as-built condition of diaphragm walls (structural slurry walls) or pile foundations can affect the performance of a civil structure supported by these elements.  The quality evaluation of foundations of these structures is most commonly performed by non-destructive testing (NDT) techniques.  The current non-destructive surface reflection techniques, such as impact echo and impulse response methods, are more economical and more conveniently performed than the techniques based on direct transmission methods, such as the sonic logging or parallel seismic methods.  Integrity of concrete piles and drilled shafts has been evaluated in the field by non-destructive surface reflection techniques for more than forty years.  Recently, impact echo methods have been applied to prototype concrete walls to identify the wall dimensions, reinforced bars, and pre-set defects.

          One-dimensional wave propagation is assumed implicitly when interpreting results of conventional non-destructive testing techniques.  In a given pile, the propagation velocity of the input stress waves is regarded as a constant, and is not a function of frequency.  The induced wavelength generally is larger than the dimension of the foundation structure.  As such, a plane wave theoretically is induced into a pile, resulting in a uniform deformation throughout the cross section.  These stress waves thus also pass through small size defects.

          More generally, waves traveling in diaphragm walls and piles include different clusters of waves, named guided waves.  These three-dimensional wave clusters arise from the incidences and reflections of a variety of compression, shear, and surface waves along the boundaries of foundation structures.  The true wave velocity is a function of frequency, and the displacement magnitudes vary along a pile or wall cross-section.  The assessment of existence and types of guided waves propagating in prototype piles has been verified recently.  Presumably, the applicability of guided waves can be extended to the non-destructive evaluations of diaphragm walls by inducing stress waves with high frequencies.

            This research provides an experimental verification of guided waves propagating in a prototype intact concrete panel.  This paper summarizes the physical properties of guided waves (Lamb waves) propagating in a plate.  The physical phenomena of dispersion relation, phase velocity, group velocity, and normalized displacement profiles in a plate are described and interpreted in detail.  To simulate guided waves propagating in in-situ diaphragm walls or precast concrete panels, the dimension of an experimental prototype concrete panel is referred to the related information based on concrete engineering design codes, the design cases of diaphragm walls, and the design cases of non-destructive testing concrete slabs or walls in laboratory.

            Frequency-controlled method is performed in guided wave experiments to induce a specific guided wave at central frequency up to 25 kHz in a concrete panel.  Guided waves are generated by an electric shaker mounted at the central point of the penal top.  The vibration responses of the panel are measured with two triaxial accelerometers set at central line and 0.71 times half thickness, respectively, of the panel top close to the electric shaker.  The group velocities of guide waves at different central frequencies are computed from the measured acceleration signals at the shaker and two triaxial accelerometers.  The time-frequency-signal intensity contour plots are demonstrated with joint time-frequency analysis (JTFA) from the time domain signals. The wave modes with larger relative displacement amplitudes in the three directions are easily excited and detected in guided wave experiments.  The 3 lower wave modes are identified on a group velocity-frequency plot by comparing to the prediction of theoretical dispersive group velocity.

            Keywords: guided wave; frequency-controlled method; mode identification; concrete panel; joint time-frequency analysis.

        1Helsin Wang, Post-Doctoral Fellow, Department of Construction Engineering, National Taiwan University of Science and Technology, Taipei 106, TAIWAN

        2Ricahrd J. Finno, Professor, Department of Civil and Environmental Engineering, Northwestern University, Evanston, IL 60208, U.S.A.

         

         

          IN-SITU TESTING OF THE PERMEABILITY OF CONCRETE

         

        I. Gabrijel, D. Mikulić, D. Bjegović, I. Stipanović 

        University of Zagreb, Faculty of Civil Engineering, Department of Materials, Kačićeva 26, 10000 Zagreb, Croatia 

        ABSTRACT 

        Reinforced concrete is one of the most widely used structural materials, because it offers good durability properties, a range of engineering solutions and a variety of aesthetic opportunities. To obtain required properties of concrete as a structural material in the laboratory and on site is not the same. Placing, compacting and curing often have a greater influence on the durability than the composition of the concrete, which is the reason why the performance of concrete cannot be only determined on the basis of laboratory testing results. Real properties of material which is placed and cured on site in different environmental conditions stay unknown. From mentioned above it is obvious that there is a strong need for the application of the non-destructive methods in testing of concrete structures on site.

             In this paper permeability properties of concrete are measured with the non-destructive methods. Methods included measuring of initial surface absorption and air permeability. Testing was performed with the two instruments developed at the Faculty of Civil Engineering in Zagreb, Croatia. Precast concrete elements and specimens casted during the production of elements are tested. Permeability properties were measured on the precast elements by the use of nondestructive test methods and on the specimens with the standard laboratory tests. Results from NDT methods and laboratory measurements are analyzed and compared, in order to evaluate the measurements techniques and the quality of the concrete. 

         

         

          Samples under repetitive stepwise compressional stress

         

        A. Kyriazopoulos1, I. Stavrakas 2, K. Ninos 2, C Anastasiadis 2, D. Triantis 2 

        1Department of Civil Engineering, Technological Educational Institution of Athens, 12210, Athens, Greece

        2Department of Electronics, Technological Educational Institution of Athens, 12210, Athens, Greece,

        Phone: +302105316525 

        ABSTRACT 

        Cement paste samples were studied using the Pressure Stimulated Current PSC technique while they were subjected to uniaxial repetitive compressional stepwise stress in the Crack Propagation Zone (CPZ) and the current emissions were recorded. Specifically, three distinguished stress steps in the same stress range (in the CPZ) were applied and after each step the stress was maintained constant for a relatively long time. The results manifest that the current is emitted in two stages. Initially, a current spike is emitted concurrently with the stress step and consequently it returns gradually to background level followed by another current emission while stress is maintained constant at the high level of each step. Each stress step causes a current peak of gradually smaller magnitude than the initially emitted. After the third repetition the stress was further increased and maintained constant until the sample failed. During this process an intense current emission was observed that decayed fast slightly before fracture. The recorded currents can be attributed to the crack opening and propagation processes while the decay of the current before fracture can be attributed to the breaking of continuation in the sample bulk preventing the current from flowing. These current emissions can be used as indices of material damage prediction.

         

          THE FIUMARELLA BRIDGE: CONCRETE CHARACTERIZATION AND DETERIORATION ASSESSMENT BY NON DESTRUCTIVE TESTINGS

         

        Raffaele Pucinotti1, Gino Mirocle Crisci2; Milena Tripodo2 , Alessandro De Lia1, Rita A. De Lorenzo3 

        1Department of Mechanics and Materials, Mediterranean University of Reggio Calabria, Italy;

         2Department of Hearth Science, University of Calabria, Italy;

        3Architect in Reggio Calabria, Italy. 

        ABSTRACT 

        In this paper the results concerning a non destructive investigation conduced in situ on a bridge built approximately on thirties in province of Reggio Calabria are reported.

        The study of ��ancient�� concrete is interesting because provides information about materials and technologies available at the time of production and the knowledge of the main physical properties of concrete and its state of conservation.

        The laser scanner technology is applied for measuring the geometrical property of structural elements of concrete bridge and the georadar technique is applied instead to the determination of the intern morphology, to the lack of homogeneity research and defectiveness and to the determination of the location of the steel reinforcements.

        The laser scanner technology allows to reproduce 3D physical models through single succeeding scanning. In this paper the laser scanner technology is utilized for the geometric survey of the concrete bridge and the solid model created by the laser scanner is acquired automatically from a finite element programme.

        Moreover the research is oriented to understand the composition of the mixture used in the casting of concrete bridge and the actual state of its deterioration and  strength.

        In fact, in add to in-situ observation and measurement of mechanical strength of concrete (penetration method, surface hardness method and ultrasonic method), in this work, the help of Hearth Science analytic techniques is considered.

        These are employed to: (i) distinguish the typologies and the composition of inerts and binder fraction and their percentage used in the concrete (ii) obtain the porosimetry of concrete in order to determine total pore volume area (MIP: Mercury Intrusion Porosimetry), (iii) estimate the amount of chemical deterioration with the determination of soluble salts (colorimetry) presents inside the material.

         

         
         
         
         
         
         
         
         

         

        SESSION 12

        INDUSTRIAL APPLICATIONS - 3 

          Use of several impact parameters at testing of compliant and rough metallic articles by the dynamic indentation method

         

        A. Rabtchevich, P. Prokhorenko, O. Matsulevich, V. Rudnitsky, S. Starshinov 

        Institute of Applied Physics, Minsk, Belarus 

            ABSTRACT

            The field of application of modern dynamic hardness testers is limited by the strict requirements for tested articles. These requirements are arisen by the nature of the dynamic indentation method and restrict the minimal local wall thickness and mass of an article around the test area to 8-12 mm (it depends on gauge) and 2.5-3 kg correspondingly. The recommended finish roughness is limited to Ra1.6-2.5. If no followed, these restrictions cause significant measurement error.

        Our investigations has shown the area of application of dynamic hardness meters can be spread if the whole process of impact is recorded and used as initial data and the data is processed by the built-in PDA. This approach is new to portable devices. It allows to develop some techniques on accounting and minimization of influence of such a negative factors. Investigations are conducted with the help of portable hardness and ultimate strength meter Impulse-2M, which records indenter velocity with 5 MHz sampling rate and stores it in the flash memory of the built-in PDA.

        One of the most widely spread factors which decreases accuracy of measurement of metallic articles with dynamic hardness testers is a roughness of tested surface. Modern instruments solve this problem by significant increase of impact energy i.e. indenter velocity or mass. The negative outcome is the increase of minimal local mass and stiffness of an article under test.

        It is possible to decrease the influence of surface roughness by measuring several impact parameters which have different sensitivity to it. We have conducted some investigations on the influence of surface finish on all main parameters of dynamic indentation. This results in a new technique of hardness measurement based on two input parameters – time of indenter intrusion into the material and velocity restitution coefficient. The technique allows to take measurements of articles with surface finish not worse than Ra4-5 with regular gauge having 9 mJ impact energy.

        The other defect of dynamic indentation testers is a restriction of local mass and wall thickness of an article. Testing of an article with insufficient mass which is not attached to sufficient mass causes irreversible article displacement and decrease of velocity restitution coefficient. Testing of an article with insufficient stiffness causes local elastic sag around the indenter. Decreasing of impact energy is not a solution to the problem as it increases accidental error of measurement due influence of surface finish and irregularity of metal properties within a volume.

        Our investigations have shown the influence of article compliance on the impact is changing during the impact. It results in less sensitivity of parameters of active impact stage (time, maximum contact force, dynamic Mayer hardness) to article stiffness, compared to velocity restitution coefficient. The experiments conducted on numerous samples with various local stiffness and mass show that dynamic Mayer hardness suits the best as an input parameter. So the instrument is calibrated in standard Brinell hardness units using dynamic Mayer hardness. Testing different samples we convince the instrument and the technique is able to measure articles with wall thickness of 5.5 mm and upper.

        As the device uses PDA it serves not only for calculation but provides user with additional services. All measurements can be marked with text comments for further identification, statistical calculations are made automatically, measurement results can be transmitted into PC for unlimited storage in specially designed database and for monitoring the state of tested objects. 

         

          Reverse engineering in industrial maintenance component criticality analysis

         

        D. Tsakatikas and G. Kaisarlis

         

        National Technical University of Athens (NTUA), School of Mechanical Engineering,

        Dept. of Mechanical Design & Control Systems, ��M�� Building, Heroon Politechniou 9, 157 80, Zografou (Athens), Greece 

        ABSTRACT 

              The paper presents an investigation of the criticality analysis applied for the classification of industrial spare parts, in conjunction with the implementation of Reverse Engineering (RE) techniques, for prioritizing the need for re-engineering equipment components for maintenance purposes. 

              In industrial manufacturing, a frequently met engineering problem is the maintenance of legacy production facilities and/or existing mechanical equipment that is still in operation and has a considerable residual service life. In most cases, the largest percentage of the total risk of the equipment overall mechanical integrity is concentrated in a relatively small percentage of its components. Therefore, emphasis is on those components which are considered critical for sustaining continuous operation in an industrial production facility. These potential high risk components require greater attention, normally achieved through the application of risk based inspection planning techniques, including NDT, that establish a consistent inspection strategy. In the paper, equipment component criticality is defined through the use of an adapted Failure Mode Effects and Criticality Analysis (FMECA) technique based on the operation and failures history record. A safety stock of the thus defined critical components is of paramount importance and must be readily available.

               

              In order to achieve that, especially in case of mechanical equipment that is out of production and is not currently supported by its original manufacturer, remanufacturing through RE techniques must be considered. One of the most critical RE tasks is the assignment of the dimensional and geometrical accuracy specifications of the reverse engineered components. These technical specifications, are established through the use of the knowledge – based system TORE (TOlerancing for RE). In the framework of a systematic methodology illustrated in the paper, they are considered, along with other relative component information (e.g. cost, delivery time), for determining if it is economically and technically feasible to manufacture and stock critical industrial spare parts.  

         

          Detection of residual curvature in electrical steel strip using a magnetic flux injection technique

         

        JP Hall* 1, AJ Moses 1, D Snell 2 

        1 Wolfson Centre for Magnetics, School of Engineering, Cardiff University, Cardiff CF24 3AA, United Kingdom

        Tel. 44(0)29 20875933, fax: 44(0)29 20879538

        2 Cogent Power Ltd., Orb Works, P.O. Box 30, Newport NP19 0XT, United Kingdom

        (* corresponding author) 

        ABSTRACT 

        A novel magnetic technique has been developed to assess the residual curvature in non-oriented electrical steel strip in the semi-processed condition. The technique is based on differences found in apparent values of the total loss from measurements made on opposite surfaces of strip material using a single yoke, flux injection type of magnetisation system. The single yoke consists of primary and secondary electrical windings wound onto a laminated, soft magnetic C-shaped core. This yoke is placed on, or near, the surface of the strip material (which is held flat) with losses associated with opposing surfaces of the strip assessed in turn. The differences in values of loss measured with the energised yoke placed on each surface have been found to be dependent on the degree of residual curvature held within the strip material. Various parameters have been assessed to optimise the sensitivity. These include the selected peak flux density, frequency of magnetisation and the physical characteristics of the magnetising yoke. Differences in loss between surfaces are also found to be dependent on strip thickness and applied tension. The technique is not strongly dependent on the gap between the yoke faces and the strip surface as loss, rather than permeability, is used as the key parameter. Total loss is not strongly dependent on the inclusion of an air gap in the magnetic circuit. This being so, the technique lends itself to having good potential to be developed as a practical method for the non-destructive evaluation of residual curvature in strip steel. 

         

          Presenting the FilmFree project and the role of HSNT in the consortium

         

        N.P. Avdelidis, K. Argyriadi, I. Prassianakis 

        HSNT - Hellenic Society of NDT, Iroon Polytechniou 9, Zografou Campus, Athens, Greece 

        Abstract 

        FilmFree is a collaborative project among different organizations within the European union. The objectives of the FilmFree project are to make a number of technological advances that will take the digital industrial radiography sector into a new era to effectively replace film as the detecting media. The Project is co-ordinated and managed by TWI Ltd. and is partly funded by the EC under the IP SME programme ref: Number NMP2-CT-2005-515746. The role of the Hellenic Society of NDT (HSNT) is mainly to provide public dissemination of information relating to the Filmfree project. The project has been in effect since October 2005 and this presentation provides details concerning results and other information for the FilmFree project.

         

         

          The effect of the angle of inclination of the exciting coil in electromagnetic-thermal non-destructive inspection

         

        N. TSOPELAS, N. J. SIAKAVELLAS* 

        University of Patras,

        Department of Mechanical Engineering & Aeronautics,265 00 Patras, Greece

        * Tel & Fax: +30 2610 997 243, E-mail address: siakavel@mech.upatras.gr

              Abstract

         

        Electromagnetic-thermal non-destructive inspection combines electromagnetic excitation and transient infrared thermography. It has been proposed as an alternative method to the classical eddy-current non-destructive testing. The effectiveness of the method when various types of coils are employed has been investigated numerically in thin conductive plates. Besides the widely used circular coils, square coils have been considered, as well as planar circular and planar square coils. This investigation has been limited till now to cases where the coil axis is perpendicular to the inspected surface. In the present work we investigate how the angle of inclination of the axis of the exciting coil affects crack detection.

           For the computations, two idealized types of coils have been considered: (i) Coils of finite length, for which it is assumed that the difference between outer and inner radius (circular coil) or outer and inner side (square coil) is very small and (ii) planar coils, for which it is assumed that the coil length is very small. We give here some results concerning the excitation of a square plate with dimensions 15 cm x 15 cm x 1 mm by: (a) A circular coil, with diameter 4 cm and length 2 cm, which will be referred as C4; (b) a square coil with side 4 cm and length 2 cm (S4); (c) a planar circular coil with inner diameter 2 cm and outer diameter 6 cm, i.e. mean diameter equal to 4 cm (PC4) and (d) a planar square coil with inner side 2 cm and outer side 6 cm, i.e. the mean length of its side is again 4 cm (PS4). The current flowing in each coil is 690 A and the number of wire-turns is 20. The plate is aluminium and lies in the (x, y) plane. The inclination angle �� of the coil axis is measured with respect to the z-axis, which is perpendicular to the faces of the plate.

           The main features that diversify two extreme cases, �� = 0o (i.e. the coil axis is perpendicular to the plate surface) and �� = 90o (i.e. the coil axis is parallel to the plate surface), are illustrated in Figures 1 and 2. Figure 1 illustrates the y-component of the current density versus x in a meridian plane and induced within the plate by each of the four coils (i.e. C4, S4, PC4 and PS4) for two angles of inclination: �� = 0o and �� = 90o. Notwithstanding the coil lift-off is always 1 mm, the coil distance from the plate varies, depending on the coil dimensions. At this point, we wish to clarify that by the term distance we indicate the distance of the mid-point of the axis of the coil from the plate. So, in the case �� = 0o, which is illustrated in Fig. 1a, the distance of the finite length circular and square coil is z = 10 mm, while the distance of the planar circular and planar square coil is z = 1 mm. In the case �� = 90o, which is illustrated in Fig. 1b, the corresponding distances are z = 21 mm for the finite length coils and z = 31 mm for the planar coils (i.e. the coil lift-off is 1 mm). Figure 1 makes clear that, when �� = 0o, the current density takes high values within a region corresponding nearly to the projection of the coil section on the plate and smaller values outside it (Fig. 1a). On the contrary, if �� = 90o, the current density takes its maximum value at the plate center (Fig. 1b). The current density distribution affects immediately the heat power, which is proportional to the square of the eddy current density, and consequently, the temperature distribution. The temperature field (isotherms) is illustrated in Figure 2, at t = 1 s. It is clear that the plate heating is most effective if �� = 0o than for �� = 90o. However, when �� = 0o, cracks situated within the central region of the projection of the coil section on the plate, may have very short detection periods. On the other hand, in most cases their shape is not clear. For the detection of these cracks, an angle of inclination of 90o must be employed. Then, the detection period increases and the crack shape become clearer. Comparing now the performances of the four coils when �� = 0o, we could say that the planar coils are most effective here. On the contrary, if �� = 90o, the coils of finite length are most effective. For that case, the square coils give better results. Intermediate angles of inclination, e.g. 45o, give worthy results only in some specific cases.


           
        (a) (b)

          Fig.1. Variation of the y-component of the current density (in A/m2) in a meridian plane and induced within the plate by each of the four coils, when the coil inclination is (a) �� = 0o, (b) �� = 90o.

           
        C4 (�� = 0o) C4 (�� = 90o)
           
        S4 (�� = 0o) S4 (�� = 90o)
           
        PS4 (�� = 0o) PS4 (�� = 90o)

          Fig.2. Comparison of the temperature distributions at t = 1 s, created by the circular, the square and the planar square coil, for angles of inclination �� = 0o and �� = 90o.

         

          The faults in Thermoelectric Power Station and the Role of Non Destructive Tests in the diagnosting processing

         

        Prassianakis K.I.1, Papadopoulos Myron2, Giorziatos Nicola3 

        1Professor, NTUA

        2ElectMech.eng.P.P.C

        3Naval eng.P.P.C 

        ABSTRACT 

        Generally, the preventive/prognostic maintenance of Thermoelectric Power Stations through Non Destructive Tests (N.D.T.) has been demostreted a very strong tool for the Turbomachine and Electromachines Technology.

        The preventive, prognostic & intervening maintenance improves also the reliability, the safe functionality, the efficiency and the economy of conventional and nuclear Thermoelectric power stations.

        The present work refers on two great categories of Faults of Power Stations:

        1. Faults/Damages from Corrosion and Erosion
        2. Faults/Damages from Fractiomechanical Fracture, specially in the below ELECTROMECHANICAL SYSTEMS:
          1. In Streamtubing of Boilers
          1. In Blades of Turbomachines
          2. In Shafts of Electromachines and Turbomachines

        We will also analyse the above faults microphenomena via the relatives micro-mechanisms. 

         

         
         
         
         
         
         
         
         

         

        SESSION 13

        THERMOGRAPHY AND DYE PENETRANTS – NDT METHODS 

          IMPACT DAMAGE CHARACTERIZATION OF GLARE® SPECIMENS BY ACTIVE THERMOGRAPHY

         

        C. Ibarra-Castanedo1, N.P. Avdelidis2, E.G. Grinzato3, P.G. Bison3, S. Marinetti3, A. Bendada1, Z.P. Marioli-Riga4, X.P. Maldague1 

        1 Laval University, Computer Vision & Systems Laboratory, Department of Electrical & Computer Engineering, Quebec City, G1K 7P4, Canada.

        2 EBETAM - Metallurgical Industrial Research & Technology Development Centre, RTD Department, A�� Industrial Area of Volos, Volos 38500, Greece.

        3 CNR – Consiglio Nazionale delle Ricerche, Corso Stati Uniti 4, Padova 35127, Italy. 

        4 Hellenic Aerospace Industry, Department of Research & Product Design, Composite Materials & Processes Laboratory, P.O. Box 23, 32009 Schimatari, Greece. 

        ABSTRACT 

        Glass Reinforced Aluminum or GLARE® is an aluminum/glass fiber laminated material whose improved physical properties confer it an interesting advantage over monolithic aluminum and composite materials for a number of aerospace applications. Nondestructive evaluation (NDE) of GLARE® however, is still a challenge, especially considering that large structures are typically sought (e.g. aircraft fuselage). In this paper, we investigated the use of infrared thermography for the assessment of impacted GLARE® specimens of several thicknesses and using different impact energy. The experimental results presented herein demonstrate that is possible to characterize the impact severity on GLARE® through active thermography techniques. 

         

         

          Making Infrared spectrum visible with infrared cameras: Advantages and applications

         

        Stelios j. Kouridakis 

        Telecommunications Systems and Applications Laboratory - Department of Electronics

        ������ of Crete - Branch of Chania, Romanou 3 – 73133 Chania, Greece, kouridakis@chania.teicrete.gr 

        Abstract 

        As a general physical rule, every system produces heat as the part of losses during the operation. The basic problem in engineering is the method and technique to detect the heat of the system and especially on specific points.

        On early years the heat control and measurement was accomplished with the use of thermal detectors. They were placed on carefully sellected positions of the system. With this method any inspection and estimation of the system was made by distributed local points. This means we don��t know what happens to every point of the system. This is sometimes unreliable or very complex during testing to estimate the behavior of the system.

        The problem has overcome last years by the development of infrared (IR) cameras. An IR camera is a useful tool for modern applications because we have images of the system produced by the distribution of heat on the surface. For the first time the heat becomes visible. We can see all the points of a system which may be in thermal stress. Thermal test and control becomes precise and reliable and each part of the system acquires its own thermal identity.

         

          the use of Grating Lock-in IR thermography for the determination of thermal properties

         

        G.Kalogiannakis1,2,H.Zhang1,J.Ravi3,S.Longuemart4,D.Van Hemelrijck2 and C.Glorieux1 

        1Lab Acoustics & Thermal Physics, Dept.Physics & Astronomy, Katholieke Universiteit Leuven, Belgium

        2Dept. Mechanics of Materials and Constructions, Vrije Universiteit Brussel, Belgium

        3Centre for Excellence in Lasers and Optoelectronic Science (CELOS), Cochin University of Science and Technology, India

        4Laboratory of Thermophysics of Condensed Matter (group of UMR CNRS 8024), University of Littoral Cote d��Opale, France 

        ABSTRACT 

        In this study, we demonstrate the use of grating lock-in IR thermography for the determination of the thermal diffusivity of composite materials. This technique is based on the use of a spatially modulated heating pattern. The latter results in the formation of a similarly modulated temperature field and the thermal properties are determined due to their influence to the modulation depth. In lock-in thermography, the excitation source is also temporally modulated at a certain frequency which results in a higher signal-to-noise ratio. This method leads to the simplification of the ill-posed problem of the thermal properties�� determination. Moreover, the right placement of the grating allows separating the influence of the diffusivities in each direction in order to obtain better accuracy.  
         

        References:

        1. Krapez, J-C, Spagnolo, L., Friess, M., Maier, H-P, Neuer, G. Int. J. Therm. Sci. 43(2004) 967-977
        2. Vaez Iravani, M. and Nikoonahad, M. Appl.Phys. 62(10) (1987) 4065-4071
        3. Kalogiannakis, G., Longuemart, S., Ravi, J., Van Hemelrijck, D., and Glorieux, C. J.Appl.Phys. 100 (6) (2006)

         

         

          Use of IR thermography for Photovoltaic Panels Performance Assessment

         

          A. Moropoulou, J. Palyvos, V. Panagopoulous, M. Karoglou

        National Technical University of Athens, School of Chemical Enginering, Zografou Campus 15780, Athens, Greece, amoropul@central.ntua.gr 

        Abstract 

        In this work infrared thermography is used for the assessment of the performance of photovoltaic panels at the façade of NTUA's Chemical Engineering building. On the southern façade and roof of the NTUA's Chemical Engineering building complex, under the Thermie Project (SE-142-97-GR-ES), it is installed a grid-connected 50 kWp solar photovoltaic array, in a standard and hybrid PV-Thermal configuration, meant to save conventional energy. 

        The thermographic system used was of 8-12�� wavelength. The thermographs obtained during the day continuously, using a standard video PAL.  The thermal images obtained showed that there are temperature differences on the PV panels, which may be attributed to PV material defects or PV malfunction.    

         

         

          The science principles of  ��dye�� penetrant��s ��building��

         

        M.L. Kazakevich 

        Institute of Physical Chemistry (SE ��KOLORAN��) NAS of Ukraine 

        ABSTRACT 

             In science literature are known a lot of ��dye�� penetrant��s compositions.  As a rule they differs each from other by the type of the dye. The first desire during new penetrant��s ��building�� is to choose the dye with bright colour and success will be provided. But the real picture is not so simple. The main part of industrial dyes are intended for cloth��s, hair��s and so on painting in necessary colour.  Thus dye is used as a constructional material. In the case of ��dye�� penetrant testing we don��t paint the controlled surface for a long time. The next operation is cleaning of the surface from dye. Thus the penetrant is better if it doesn��t paint the controlled construction. From the other side penetrant  must very active interacts with the surface to have the best penetrate properties. Such contradictions make penetrant��s ��building�� a very complicated task.

            We suggested a new approach to ��dye�� penetrant��s elaboration, which include the optimization penetrant��s properties by the dye with special chemical structure. Synthesis of the  dye allows to influence almost on all main properties of the penetrant:

        • spectroscopic characteristic and consequently the sensitivity of capillar control;
        • the faculty to penetrate into defects. The decisive influence on this property depends on the solvent��s nature. And one of the main tasks of penetrant��s ��building�� is the dye��s modification to combine it with different solvents;
        • adhesion of the dye to the controlled surface, which too depends on  it��s chemical structure. The adhesion lowering permits to increase the quality of surface��s cleaning and to use the water wash technology;
        • toxic and ecologic safety.

            After use of such approach we elaborate the dye, which possess a complex need properties:

            -     bright raspberry colour;

        • extinction coefficient near 50000;
        • simply washed by water;
        • solve in different solvents in high concentration.
        • one  of  the  main  advantages  of  the  dye  is the full absence of any harm and ecological cleanliness of the dye because it��s synthesized from medicine raw materials.

            Complex decision of the task allowed us to ��build�� the set of dye penetrants for different branches of industry and energetic. For control of welding in vessels on nuclear power stallions and ships we suggest the nontoxic penetrant on water base, for NDT of airspace and aviation constructions - penetrant on kerosene and lubricants, for aerosol products – on alcohol and so on. Among this set there are ��dye�� penetrants with the record sensitivity of control – defects with the breadth about 0,5 m��m can be detected.  All of them are certificated and standardized in Ukraine and produced by state enterprise ��KOLORAN�� of National Academy of Science of Ukraine. 

         

         

          Near infrared (NIR) imaging for NDE

         

            DIAMOND – G.G, D.A. HUTCHINS, P. PALAV

         

             
         
         
         
         
         

         

        POSTER SESSION – 1

         

         

          Application of Acoustic Emission Method for Contact Damage Identification

         

        Pavel Mazal, Luboš Pazdera

         

        Brno Unversity of Technology, Brno, Czech Republic 


         
         
        Fig.1 Exemple of pitting on the surface of experimental specimen (bearing steel)

        One of important reasons for loss of decisive properties of all types of bearings and gear transmissions is the inception of point contact damage, so called pitting (Fig.1), on some of the elements in contact. This type of damage is caused by cyclically repeating processes in surface layer of material by mutual dynamic load of two bodies. Damage of surface layers causes inception of micro-cracks in places of maximum sheer stress by progressive separating of damaged surface layers and by inception of holes on the surface. In the beginning, this fatigue damage results in decrease of functional properties of the damaged part; however, emerged surface hole may gradually create a centre of fatigue crack, which successively enlarges to the whole section of the part. In some applications, damage of these elements might cause considerable material loss and most importantly it might endanger lives of people.

        Taking into account the importance of contact damage, attention is paid to chosen types of elements in contact; their warming is measured, total level of noise and vibration of the system are analysed. One of promising possibilities of observing the damage course of material exposed to cyclic contact loading is using the acoustic emission technique (AE). In the signal monitored on the surface of elements, it is possible to identify the course of a number of processes that appear both on the surface and inside the material of the construction.

        This contribution will summarise the experimental experience of authors with acoustic emission method application in the area of improved contact damage stages identification on material testing stations Axmat and Rmat types (fig.2) and first results received from real bearings measurements.

        The results prove the AE technique enables reliable recognition of running-in period, stabilised run and exact definition of origin stage of surface damaging, leading to the pitting. It is verified very important direction of AE analyzers utilisation not only in research area, but that the AE technique may be successfully used even in routine industrial practice.


         
        Fig.2 Illustration of AE signal activity in contact fatigue test (AE counts vs.time).
         

        Method of acoustic emission may offer another possibility of deepening of diagnostics of real actual state of bearing and gears; it is, without doubt, one of the new perspective areas of automated diagnostics.

        Presented results are carried out in the framework of the project of Grant Agency of the Czech Rep. nr. 106/06/0343 „Research of stages of contact damage using the AE method�� and partly the project of MPO CR F1-IM3/136 „Research of new methods of measuring and evaluation of Acoustic emission signal...��.

         

          MONTE CARLO SIMULATIONS FOR NON-DESTRUCTIVE ELEMENTAL ANALYSIS OF LARGE SAMPLES BY NEUTRON ACTIVATION ANALYSIS

         

        F. Tzika1 and I. E Stamatelatos 

        Institute of Nuclear Technology and Radiation Protection, NCSR 'Demokritos', Aghia Paraskevi Attikis, 15310, Greece

        1email: faidra@ipta.demokritos.gr 

        ABSTRACT 

        Instrumental Neutron Activation Analysis (INAA) is an established nuclear analytical technique with applications in a broad range of scientific and technological fields. Typically, conventional INAA involves analysis of small material portions of 10 to 100 g in mass. However, analysis of samples of a larger mass implies a number of additional advantages such as (a) analysis of objects too precious to remove small parts from and (b) minimization of representative sampling problems of heterogeneous materials.

              In this work, a method to perform in depth, non-destructive, multi-element INAA of samples of large volume (up to 1 L) is presented. The technique has been developed at the Research Reactor Laboratory of NCSR 'Demokritos'. The Large Sample Neutron Activation Analysis (LSNAA) technique involves sample irradiation in the reactor��s thermal neutron column and subsequent measurement of the induced radioactivity in the sample employing a HPGe based spectrometry system. Correction algorithms, to compensate for the effects of (a) thermal neutron self-shielding within the sample, during sample irradiation and (b) source geometry and gamma ray attenuation by the sample material during gamma ray counting, have been developed. The correction methods were based on Monte Carlo simulations of both the irradiation and counting facilities using the MCNP computer code. Correction factors for neutron self-shielding, gamma-ray attenuation and volume distribution of the activity in large volume samples representing industrial and archaeological materials are presented and the application of the LSNAA technique is demonstrated.

        Large sample neutron activation analysis compliments and significantly extends the analytical tools available for applications requiring in-depth, non-destructive, multi-element analysis of materials too precious to damage for sampling purposes (whole object analysis), representative sampling of heterogeneous materials, or analysis of samples of arbitrary shape. Potential applications of the technique are environmental protection, industrial waste, advanced technological materials, as well as cultural heritage and authentication studies. 

         

          Modelling of time reversal focusing techniques in pipes

         

        C. Ennaceur, T-H Gan, R. Sanderson, P. Mudge 

          CHARACTERIZATION OF RADIOACTIVE WASTE DRUMS

          BY NON DESTRUCTIVE GAMMA SPECTROMETRY

         

        A. Savidou*, F. Tzika and I. E. Stamatelatos 

        Institute of Nuclear Technology and Radiation Protection, NCSR ��Demokritos��,

        15310 Aghia Paraskevi, Attiki, Greece

        Corresponding Author: savidou@ipta.demokritos.gr 

        ABSTRACT 

        Assay of the radioactive content of waste drums is important for inventory and waste disposal purposes. The sampling of the drum content is a difficult, time and labour consuming procedure, involving special radiation protection considerations. On the other hand the characterization of waste drums containing radioactivity by measuring the drum as a whole (without opening) offers overall simplicity while minimizes labour and radiation protection requirements.

        In the present work a non destructive technique based on gamma spectrometry was used to assay radioactive waste in drums.  For this purpose a portable NaI detector was utilized. The Gamma ray detector efficiency for the volume source was derived by Monte Carlo simulations using the MCNP code. The code was used to perform numerical simulations taking into consideration the energy of the gamma ray emitter, the matrix material, the detector efficiency, the geometric configuration employed, the size of the drum, and the wall material and thickness of the drum.

        The technique was verified by estimating radioactivity levels in drums containing ion exchange resin waste from the water demineralization system of GRR-1 open pool-type research reactor facility at NCSR ��Demokritos�� as well as in drums containing solidified radioactive sludge. Satisfactory agreement was observed by comparing the results of the non destructive method against analytical results of samples obtained from each drum.

        The simulations of the present study can easily be extended to model other materials and container types and sizes as well. Therefore, the technique can also be applied in other radiation protection applications such as biological radioactive waste from hospitals or other physical forms materials that can be met in radioactive waste.

         

          NON-DESTRUCTIVE ANALYSIS OF BULK CONCRETE SAMPLES USING PROMPT GAMMA NEUTRON ACTIVATION ANALYSIS

         

        I.E. Stamatelatos, D.��. Nanopoulos, K. Kasviki, F. Tzika and A. G. Youtsos 

        Institute of Nuclear Technology and Radiation Protection, NCSR ��Demokritos��

        Aghia Paraskevi, Attikis, 15310, Greece

        1E-mail: ion@ipta.demokritos.gr 

        ABSTRACT 

        The calibration and evaluation of a prompt-gamma neutron activation analysis (PGNAA) system for non-destructive elemental analysis of bulk concrete samples is discussed. The system incorporates a 185-GBq Pu-Be radionuclide neutron source within a graphite neutron collimator and moderator assembly. Prompt-gamma rays produced by neutron capture reactions in concrete were detected by a HPGe semiconductor detector of 10% relative efficiency. Two C25/30 concrete samples of 151515 cm3 were obtained from the National Technical University of Athens and analyzed. Silicon and calcium were quantified by analysis of the 4.935 and 6.420 MeV lines, respectively. Appropriate corrections for neutron and gamma-ray self-attenuation in the sample were applied. The corrections were based on Monte Carlo simulations of the source, collimator, sample and detector configuration performed using the Monte Carlo Neutron Photon code MCNP-4C2 with nuclear data from the ENDF-B/VI library. An excellent agreement was observed between the lime/silica ratio determined by PGNAA and calculated from the sample ingredients in the pre-mix phase. Further capabilities of the technique related to quantification of hydrogen and chlorine in concrete by analysis of the gamma lines at 2.22 and 6.11 MeV, respectively, are discussed. The results of this study demonstrated the feasibility of developing an ��in situ�� PGNAA technique facility for non-destructive bulk elemental analysis of concrete.

         

          The state equations for the first and second fundamental problems of elastodynamics for a cracked medium

         

        Bardzokas D.I., Sfyris G.I. 

        Abstract 

        In our work we will derive the state equations the first and second fundamental dynamical problems in the frame of linear elasticity.  In the first fundamental dynamical problem we will consider an infinite medium that contains a crack, on the lips of which, the stresses are considered to be known. The second fundamental problem has the same formulation, but in this case, the displacements on the crack lips are known. Beginning from the equations of motion, Hooke��s law and the compatibility equations we will derive the state equations for the above mentioned problems. The derivation of the equations will be based on the Muskhelishvili method of the Complex Potentials, the use of the Sohotsky – Plemely formulas and finally we will get two singular integral equations that are the state equations for the problems. These equations may contribute to better and further study of problems of seismic and fracture mechanics, composite, cracked or multiply connected media.

         

         

          Application of cross-correlation and wavelet de-noising techniques for the reduction of dispersion effects in guided ultrasonic signals

         

        TAT – HEAN GAN, ROBIN MALLETT, PETER MUDGE

         

          EXPERIMENTAL APPLICATION OF 3-D TERRESTRIAL LASER SCANNING AND ACOUSTIC TECHNIQUES IN ASSESSING THE QUALITY OF STONES USED IN MONUMENTAL STRUCTURES

         

        Casula1,  Fais S.2, Ligas P.2 

        1INGV- Istituto Nazionale di Geofisica e Vulcanologia – Centro Nazionale Terremoti - Bologna (Italy)

        2 Dipartimento di Geoingegneria e Tecnologie Ambientali - University of Cagliari – Cagliari (Italy) 

        ABSTRACT 

        Early identification of damage and degradation of monumental structures is essential in assessing and monitoring their status and in planning their restoration. Therefore an effective non-destructive evaluation (NDE) is urgently required. This paper briefly describes the preliminary results of an experimentation aimed to test a new non-destructive methodology based on the integrated application of 3-D terrestrial laser scanning and acoustic techniques in the ultrasonic range (54 kHz) in evaluating the quality of stone materials. Our target is to evaluate the state of conservation of stone building materials by correlating ultrasonic longitudinal pulse velocity and frequency spectra with the reflectivity or reflectance of the reflected 3-D laser scanner beam pulse transmitted to the target of an investigated surface. 
         

        Sonic or ultrasonic methods are very effective in detecting the elastic characteristics of stone materials and thus their mechanical behaviour even though data interpretation is very complex as elastic wave velocity heavily depends on moisture, heterogeneity, porosity and other physical properties. Accurate ultrasonic signal processing procedures based not only on pulse velocity analysis but also on frequency spectra analysis have improved the results of our analysis and given objective and quantitative information on the condition of the investigated materials.

        The 3-D laser scanners used in terrestrial and airborne applications can be considered highly automated total stations with lasers optimised for high speed surveying as sensors. By means of these instruments point clouds can be acquired densely sampled from the surface of a target object. The travelling time of the laser pulse is converted into the distance between the instrument and the investigated object. The distance and direction of the acquired laser pulse are then converted into coordinates of the part of the target surface at which the scanning pulse is reflected.

        The 3-D automated total stations whose sensors are lasers optimised for high speed surveying, by means of these instruments points cloud can be acquired densely sampled from the surface of a target object. In particular, the travelling time of the laser pulse is converted into a measure of distance between the instrument and the object to investigate. The distance and the direction of the laser pulse acquired are then converted into coordinates of the target surface part at which the scanning pulse is reflected. 

        As a matter of fact, the result of a laser scanning survey is a very dense cloud of points whose positions are known in an arbitrary reference frame. The X, Y, Z coordinates and the reflectivity value for each point are acquired and recorded, providing the area coverage necessary for the 3-D reconstruction and characterisation of the surveyed object. 
         
         
         

        The data processing of the laser scanning technique consists of the set of operations needed to obtain a digital model of a surveyed object starting from the different point clouds. A two-step procedure is needed, including the pre-treatment of the data followed by the solid modeling of the point cloud.

        In this paper, the integrated interpretation of the acoustic and 3D laser scanner data acquired in an interesting sector of an old church built mainly in limestone of different chemical-mineralogical composition and mechanical properties, and restored over the past decades, is useful due to peculiarities of the two methods. The integration of the data of a different nature provided a good knowledge of the investigated monumental structure and an evaluation of the effectiveness of the restoration.

         

         

          A non destructive study on Albanian Byzantine and post-Byzantine icons

         

        E. Franceschi1, D. Nole1 and L. Glozheni2 

        1Department of Chemistry and Industrial Chemistry, University of Genoa, Italy

        2 National Museum of Medieval Art, Korçe, Albania 

        Abstract 

        X-ray fluorescence and spectrophotometry techniques were used to study the inorganic pigments in several Albanian Byzantine and post-Byzantine icons. This work is a part of a project regarding a non destructive study carried out on the icons collected in an important Albanian Museum, the Museum of Medieval Art of Korçe in the south-east of the Country. The artworks are of various periods and artists, some named and others anonymous. Amongst them, we may single out icons of the 13th and 14th century and masterpieces executed by leading painters such as Onufri, Nicolas, Onufri Qiprioti, Konstantin the Teacher, Konstantin the Hieromonk, Konstantin of Spatheia, David of Selenica, and the çetiri brothers, a family of painters from Korçe, as well as other pieces created by painters who worked in Albania and elsewhere. Any withdraw of painting samples was not taken. From ten to twelve measurements for each painting have been performed to characterize the different pigments. The results obtained during this work allowed us to identify the palettes of the authors of the icons studied. 

        References:

        Artist��s pigments. A Handbook of their history and characteristics, vol. 2,  Ashok Roy Editor, Oxford University press, 1986

        N. Civici, O. Demko, R.J.H. Clark, Journal of Cultural Heritage 6 (2005) 157-164

        N. Civici, Journal of Cultural Heritage 7 (2006) 339-343

        C. Franceschi, L: Glozheni, I. Cascone, D. Nole, E. Franceschi, Non-destructive and Microanalytical Techniques in Art and Cultural Heritage Research, Lisboa, Portugal, 25-28 April 2007.

         

         

          ELASTIC WAVES IN SOLIDS WITH PROTECTIVE LAYER

         

        A. Baev, P. Prokhorenko, K.Filippov, O.Karabukhina 

        Institute of Applied Physics, Minsk, Belarus 

              ABSTRACT 

              There are many articles belonging to the layered objects and it is actually to inspect the contacting materials structure and detect the volume discontinuities and cracks in them.   In our work new distinctive features of the elastic wave propagation in solids with protective layer (PL) have been studied experimentally and the results are considered for application in ultrasonic inspection.  The first part of the work is devoted to the experimental research of the acoustical path of ultrasonic echo-method when a probe is moving in x direction along the article surface with PL and a defect (reflector) is under protective layer in steel base. It is proposed that the PL thickness hp, where p is the length of ultrasonic wave in the layer.  For this case the function of the signal propagation can be presented as ND1D212, where D1 and Dare the coefficients of the sound transmission from the probe into the steel body base (through the PL) and back, 1 and 2 are the directivities of the probe and the reflector in steel.

              We have obtained dependencies of the echo-signal amplitude PA vs. PL thickness, wave frequency f=1.8_5 MGC, exit angle in the steel base of the specimen =0_600. The obtained data show that the dependence of PA on h*=h/p for longitudinal, transverse and head waves, excited and propagated in the steel, have substantial oscillations (up to10 dB) caused by interference phenomena. It should be noted that there are conditions (h*, f, ) at which function PA(x) have two maximuma. This effect is explained by concurrence of the factors, described by coefficients Di and i incoming in expression for N. The method of the acoustical path stabilization when interference phenomena in protection layer are to be appear has been developed. To diminish oscillation of PA vs. h* we suggest to use the additive acoustical echo-canal (path), created by the additive probe installed in a common corps. An optimal frequency fc of the second probe is determined from the derived formula and depends on the former parameters (h*, f, ) as well as boundary conditions at the interfaces probe-PL-steel.

              The second part of our work is devoted to the method development of head waves apply for measure h, cracks depth H0 and acoustical properties of contacting materials with PL thickness varying. To increase the methods sensitivity and accuracy the small aperture probes (as receivers) have been developed and used. Let the coordinate of a crack is x=0, of  receivers probes - xand x2 , emitter probe – x3.  Then the theoretical and experimental data of the H0  measuring show that if   x3>x1> 0,  x2 <0  the sensitivity is obtained when {x3, x1, x2 }0.  But when x3>0, x2<x1<0 the maximum sensitivity is when {x3,  x1}0 , and x2 . Using the suggested method and the developed arrangement it is possible to expand the range of the cracks depth, measured by ultrasonic, from 20_30 mm up to 0.5_1 mm.

         

          REFLECTION OF ACOUSTIC BEAM FROM THE SOLID SURFACE WITH INHOMOGENEOUS BOUNDARY CONDITIONS

         

        P. Prokhorenko, A. Baev, M. Asadchaya 

        Institute of Applied Physics, Minsk, Belarus 

        ABSTRACT 

        There are different amplitude, spectral, phase methods of ultrasonic inspection and their combinations to evaluate quality of adhesion or cohesion of joints of layered solid materials. Some difficulties of the former methods application are to be arise when contacting materials have varied structure and ultrasonic attenuation in a volume, substantially various elastic properties  (for example resin-metal), high roughness of the exit surface, one-sided access and etc. Sometimes it is necessary to decrease inspection time and to simplify methods used. To overcome the former difficulties the idea [1], based on peculiarities of the simultaneous beam reflection from the joints surfaces with various boundary conditions,   have been proposed [1].

        This work is devoted to theoretical and experimental study of the new distinctive features of the elastic waves reflections from the interface S of two contacting materials with inhomogeneous boundary conditions: free-rigid; free-slip; slip-rigid; rigid-slip, where S= and Si is proper to uniform boundary conditions. Acoustical field () of reflected ultrasonic waves may be imagined as a sum of acoustic fields of two or more imaginary coherent ultrasound emitters with different phase shift i and wave amplitude Ai, and aperture Di, depending on the ultrasonic probe position too.  It was shown that there are such conditions, including Di, beams incident angle I and reflected one , signal frequency , time duration of ultrasonic pulses , at which acoustical field of reflected beam undergoes substantial modifications: shift of the () angle maximum and appearance of two or more additive maximums (minimums); ��rotation�� of the beam incidence plane and etc. So, it is possible to create conditions when amplitude of the signal, reflected from the inhomogeneous boundary (part of which is defect), falls down by 20-40 dB. The same or more amplitude variations can be achieved when small adhesion defect Si is inside S region and =Si /S=*. It should be noted that laboratory findings are in good accordance with theoretical data.

        The conducted studies have revealed that volume; surface; subsurface, plate and etc. waves can be used for implementing the high-sensitive method for control of adhesion of materials that is based on the principles of creating optimal conditions for superposition of fields of imaginary coherent sources.

        This material is based upon work, supported by Fond of Foundation of Republic Belarus. 
         

        References:

        Baev, A., Abstracts of Int. Conf.: Ecology and waves. – Belarus, Minsk, 1993. p.95.

         

         

          PHYSICAL ASPECTS OF THE CAPILLARY CONTROL THEORY

          (LIQUID PENETRANT TESTING)

         

        Peter Prokhorenko 

        Institute of Applied Physics of the National Academy of Sciences of Belarus,Minsk, Belarus  

        ABSTRACT 

        The liquid penetrant testing, and its capillary variety, and control of airtightness, are based on the filling by the liquid defectoscopic substances of capillaries and capillary-porous bodies. Physicomechanical interaction on the boundary liquid - solid body influences seriously the eventual result of control. We investigated phenomena, as interaction in the capillary of two chemically nondestructive liquids, mechanism of double-sided filling of blind capillaries, ultrasonic capillary effect, size effect of viscosity. Their role in an increase of the effectiveness of the development of defects and productivity of control is shown.

        The knowledge of laws governing these phenomena does make it possible to create the theory of the motion of liquids in capillaries from macro to micro sizes, does make it possible to govern the operations of control, gives possibility for creating of new defectoscopic materials and new testing methods.

        Some scientific positions were partially reported at the World Conferences on the nondestructive testing: Delhi (India, 1996), Rome (Italy, 2000), Montreal (Canada, 2004) and the European conferences: Nice (France, 1994), Copenhagen (Denmark, 1998), Barcelona (Spain, 2002), Berlin (Germany, 2006) and also at the American Conferences on the nondestructive testing "Review of Progress in Quantitative NDE" (1998-2004). Basic principles of the capillary control theory, including physical aspects and bases of hydrodynamics of liquid media in the capillaries are presented in the monograph (Prokhorenko P, Migoun N, Stadthaus M. "Theoretical Principles of Liquid Penetrant Testing" Berlin, 1999, 252 p. (book). 

         

             
         
         
         
         
         

         

        POSTER SESSION – 2

         
         

          Crack Diagnosis in Plates Using Propagated Waves and HHT Transform

         

        M. H. Soorgee1, A. Yousefi-Koma2

         

        1Graduate Student, Advanced Dynamic and Control Systems Lab, School of Mechanical Engineering,

        University of Tehran, Tehran, Iran, mhsoorgee@yahoo.com

        2Assistant Professor, Advanced Dynamic and Control Systems Lab, School of Mechanical Engineering,

        University of Tehran,Tehran,Iran, aykoma@ut.ac.ir 

        Abstract 

        Keywords: Piezoelectric, Hilbert Huang Transform, Wavelet, Health monitoring 

        This paper is a numerical simulation and verification of health monitoring of plate structures using propagating waves. The goal is to detect the location of a linear crack in a plate using a piezoelectric actuator/sensor pair based on the time-of-flight of propagating waves. The actuation signal is selected due to the dispersion curve of the aluminum plate. The commercial finite element code (ABAQUS) has been employed to model a plate with piezoelectric actuator and sensor and a tiny groove representing the crack. After a transient dynamic analysis, the sensor voltage has been acquired. Using Hilbert Huang Transform (HHT) method, from the time-energy spectrum of sensor response, the arrival time of the incident and reflected waves to the sensor has been computed. Based on the time-of-flight of the propagated waves, the wave speed was obtained by dividing the propagated distance by the arrival time of the incident wave. Having computed the wave speed, the locus of the crack was determined as an ellipse with the actuator and sensor as the foci. Changing the location of the actuator/sensor pair, three ellipses were obtained and their intersection was considered as an approximation of the crack location. A wavelet analysis has also been employed to validate HHT results. There was good compatibility between numerical simulation and the experimental work done by Tua et al (2004).

         

          VERIFICATION OF COMPUTATIONAL ELECTROMAGNETIC PROGRAMS – THE SPECIAL CASE OF TEAM WORKSHOP PROBLEM 15 (RECTANGULAR SLOT IN A THICK PLATE): PRESENTATION OF A PROBLEM IN NON DESTRUCTIVE EVALUATION

         

        John K. Sakellaris, , I.N. Prassianakis1, G. Tsamasphyros1, Y. Hoon Shin2, H. Young Seo2 

        1National Technical University of Athens, Greece

        2Korea Eddy Current & Ultrasonic Co. Ltd., Korea 

        ABSTRACT 

        Inversion of eddy-current data and the reconstruction of flaws is the preeminent problem in electromagnetic nondestructive evaluation (NDE). This places a premium on developing good forward models for computing field-flaw interactions, because all inversion algorithms must, of necessity, rely on such calculations. There has evolved in recent years several sophisticated computational models for the forward problem [1-4], but these models differ significantly in their theoretical and numerical approaches. For example, [1-3] use a volume-integral approach that incorporates fast Fourier transforms with conjugate gradients to solve the resulting linear system of equations, whereas [4] uses finite-elements. Because of this diversity of theoretical-computational approaches, it has become clear that there is now a great need to present experimental data from benchmark problems, whose purpose is to not only validate individual models and codes, but to also allow comparisons between competing models and codes. In this paper we present two such problems for the calculation of impedance change, Z. These problems,

        1. Rectangular slot in a thick plate (900 Hz)

        2. Rectangular slot in a thick plate (7 kHz), have the common feature of being based on practical eddy-current testing techniques, and of utilizing simple geometries.

        Additional problems of this genre, including cracks in a thin plate, cracks in a double plate system, and cracks in a thin plate with a tangent coil, are collected together in [6]; further details of each experiment can be found in the references cited in this paper.

        PROBLEM NO. 1

        The experimental arrangement is shown schematically in Figure 1. Here, a circular air-cored coil is scanned, parallel to the x-axis, along the length of a rectangular slot in an aluminum alloy plate. Both the frequency and the coil lift-off are fixed and Z is measured as a function of coilcenter position. The parameters for this test experiment are listed in Table 1. This problem is completely described in [7], and is also included in [5]. Solutions appear in [3,8], where a volume-integral equation is used. Preliminary calculations for this case were first reported by Dunbar [9].

        PROBLEM NO. 2

        The rectangular slot geometry for this problem is identical to that of Problem No. 1. The experimental arrangement uses a larger coil, at a higher frequency. The skin depth at this frequency is one-fifth of the slot depth, which makes this problem differ from No.1 by nearing the thin-skin limit. Theoretical calculations for this problem have been published [8].

        OBJECTIVE

        The objective is to compute the change in the inductance and resistance of the driving-point

        impedance of the coil (compared to its value over an unflawed portion of the plate) as a function of coil position, and compare the computed results to the experimental results. This is to be done for each problem. In addition, the computed and experimental results are to be compared by plotting the magnitude and phase of each versus coil-center position. Plot the magnitude and phase (in degrees) on separate graphs, for each test. The magnitude and phase are given by: 

        where XL=L. 

        REFERENCES

        1. J. R. Bowler, L. D. Sabbagh, and H. A. Sabbagh, "A Theoretical and Computational Model of Eddy- Current Probes Incorporating Volume Integral and Conjugate Gradient Methods," IEEE Trans. Magnetics, Vol. 25, No. 3, May 1989, pp. 2650 2664.

        2. H. A. Sabbagh, L. D. Sabbagh, and J. R. Bowler, "A Volume-Integral Code for Eddy-Current Nondestructive Evaluation," COMPEL-The International Journal for Computation and Mathematics in Electrical and Electronic Engineering, Vol. 9 (1990), Supplement A, pp. 67-70.

        3. J. R. Bowler, S. A. Jenkins, L. D. Sabbagh, and H. A. Sabbagh, "Eddy-Current Probe Impedance Due to a Volumetric Flaw," J. Applied Physics, Vol. 70, No. 3, 1 August 1991, pp. 1107-1114.

        4. W. Lord and R. Palanisamy, in G. Birnbaum and G. Free, eds., Eddy, Current Characterization of Materials and Structures, ASTM STP722 (Amencan Society for Testing and Materials, Philadelphia, 1981), pp. 5- 81.

        5. H. A. Sabbagh, ed., "The ACES Collection of Canonical Problems: Set 1," The Applied Computational Electromagnetics Society, Spring 1990, pp. 3-8.

        6. Applied Computational Electromagnetics Society Newsletter, Volume 6, No. 1, March 1991, pp. 17-34.

        7. S. K. Burke, "A Benchmark Problem for Computation of Z in Eddy-Current Nondestructive Evaluation (NDE)," J. Nondestructive Evaluation, Vol. 7, Nos. 1/2,1988, pp. 35-41.

        8. D. McA. McKirdy, J. Nondestructive Evaluation, Vol. 8 (1989), pp. 45-51.

        9. W. Scott Dunbar, J. Nondestructive Evaluation, Vol. 7 (1988), pp. 43-53.

         

          Damage prediction using response surface metamodels and electromechanical admittance signatures

         

        C. P. Providakis and M. E. Voutetaki 

        Applied Mechanics Lab, Department of Applied Sciences

        Technical University of Crete, GR-73100 Chania, Greece

        Email: cpprov@mred.tuc.gr, URL: http://www.mechanics.tuc.gr 

        ABSTRACT 

        In the present work, a health-monitoring technique based on the electromechanical admittance approach is numerically presented and applied to civil engineering structures using statistical metamodeling methods. A procedure is developed for damage detection and identification as applied to a concrete sample. The detection and identification of damage is accomplished by using statistics surfaces to build the metamodels.

        Piezoceramic transducers (PZTs) are extensively used in vibration and noise control, and damage detection of various engineering structures. The last decade has been applications of PZT-host structure interaction models in electromechanical impedance (EMI) techniques. In the EMI techniques, the PZT is either surface bonded or embedded inside the host structure. The governing principle in these techniques is that the PZT actuates harmonically in the presence of the electric field to produce a structural response which is known as ��admittance signature��.  The changes in the admittance signature, which is the inverse measure of the mechanical impedance of the structure, are indicative of the presence of structural damage.

        Metamodels have been used with success in many areas of engineering for decades but there is a limited amount of work in the field of damage detection. In this case, a metamodel is a reduced order model constructed by fitting a model to a set of points in the design space using a statistically design of experiments approach. Then a polynomial-type model is fit to the points using a multiple regression fitting technique. This fit allows models to be constructed that relate damage parameters of interest (such as damage severity and its location) to measurable output features (e.g. electromechanical admittance signatures).

        In the present paper, the proposed damage prediction and identification methodology has been demonstrated and its success quantified for the case of a 3-D numerical specimen of a concrete cantilever plate. 

         

          X-ray microtomography as a nn-destructive tool for stone characterization in a conservation study

         

        Elke Van de Casteele1, Simone Bugani2, Mara Camaiti3, Luciano Morselli2, Koen Janssens4 

        1SkyScan, Belgium

        2Department of Industrial Chemistry and Materials, University of Bologna, Italy

        3CNR - Institute for Conservation and Enhancement of Cultural Heritage, Italy

        4Department of Chemistry, University of Antwerp, Belgium

        elke.vandecasteele@skyscan.be 

        ABSTRACT 

        Calcareous stones such as Lecce stones have a high porosity which results in a readily uptake of rainwater. Due to the atmospheric pollutants dissolved in the water these stones, used in a lot of historical buildings, are constantly under attack which leads to a decay of the stone. Different kind of organic hydrophobic products such as Paraloid B72 and fluorinated rubber are often applied as protectives with the aim to reduce the corrosion of the material. In order to study the manner in which these treatment products fill the pores a desktop X-ray microtomography system was used. This technique allows the 3D investigation of the internal structure of the stone in a non-destructive way. In this research morphological parameters such as the total porosity, pore size distribution and wall thickness distribution were calculated before and after treatment in order to evaluate the changes induced by the polymer application. 

        Keywords: X-ray micro-CT, Lecce stone characterization, conservation products

         

         

          A PRELIMINARY ESTIMATION OF ANALYSIS METHODS OF VIBRATION SIGNALS AT FAULT DIAGNOSIS IN BALL BEARINGS

         

        P.N. Botsaris, D.E. Koulouriotis  

        panmpots@pme.duth.gr, jimk@pme.duth.gr

        Democritus University of Thrace

        Polytechnic School

        Department of Production Engineering and Management

        Building of Library, 67100, Kimmeria, Xanthi 

        ABSTRACT

              In this paper a preliminary estimation of the most common analysis methods of the vibration signals of a ball bearing is tried. The tested methods are the typical statistic analysis method, the Fourier transform, the frequencies spectrum analysis and the Wavelet method. Further testing under variable and/or radial loads is under investigation by the present research team before a final conclusion can be made.

         

        Key words: bearings vibration, vibration analysis methods

         
         

          THEORETICAL EVALUATION OF THE ELASTIC MODULUS OF PARTICULATE COMPOSITES BY THE CONCEPT OF INTERPHASE AND COMPARISON WITH DESTRUCTIVE AND NON-DESTRUCTIVE EXPERIMENTAL RESULTS

         

        E. Sideridis, G. D. Bourkas, V. N. Kytopoulos and I. N. Prassianakis

         
         

        National Technical University of Athens, Faculty of Applied Sciences

        Department of Mechanics, Lab. of Strength and Materials

        Zografou Campus,

        GR-157 73, Athens, Greece

        ABSTRACT

         

             In this work the elastic modulus of particulate composites is evaluated by taking into consideration the existence of an interphase between matrix and filler.

              For this purpose basic models as cube-within-cube and square-into-square formations are used. It has been found that by considering the interphase as a third phase, consisting of a zone between matrix and filler with mechanical properties varying between those of filler and matrix, the elastic modulus value increases. The theoretical values are compared with tensile experimental results and ultrasonic measurements as well as with those derived from existing formulae in the literature. Although the elastic modulus values increase by considering the influence of an interphase, however remain close to the tensile experimental results that are situated well below the values derived from ultrasonic measurements. 

         

          AN INTERMEDIATE ADHESION QUALITY MODEL FOR THE EVALUATION OF STRENGTH AND INHERENT FLOW OF RESIN / FILLER SYSTEMS

         

        G. Bourkas 

        National Technical University of Athens, Faculty of Applied Mathematical and Physical Sciences, Department of Mechanics, Laboratory of Testing and Masterials

        Zografou Campus, GR – 15773, Athens, Greece 

        ABSTRACT 

        The tensile strength of particulate composites has been evaluated for the case that adhesion exists between matrix and filler by using a model consisting of four components, on the basis of cube-within-cube formation. Additionally the ��inherent flow�� of the composite has been estimated with respect to the ��inherent flow�� of the matrix , for the case of resin / filler systems. By comparing the theoretical results of the strength with experimental data for untreated particles in epoxy / filler systems, the model under consideration has been characterized as corresponding to intermediate adhesion quality between matrix and filler, since a satisfactory agreement between theory and experiments has been observed for the case of untreated particles of intermediate strength values. The systems used to compare the strength were resin / iron and resin / glass beads particulate composites. The strength values predicted by the present procedure are in agreement to those provided by an existing evaluation method in the literature. 

         

          STRENGTH OF RESIN / FILLER SYSTEMS USING

          TWO MODELS i) OF PERFECT and ii) OF LOW ADHESION QUALITY

         

        G. Bourkas, E. Sideridis, C. Younis, J. Prasianakis, V. Kitopoulos 

        National Technical University of Athens, Faculty of Applied Mathematical and Physical Sciences

        Department of Mechanics, Laboratory of Testing and Masterials, Zografou Campus

        GR – 15773, Athens, Greece 

        ABSTRACT 

        The tensile strength of particulate composites has been evaluated for the case that adhesion exists between matrix and filler. Two models, each of three components on the basis of cube-within-cube formation, have been used as representative volume elements. By comparing the derived theoretical results with experimental data for treated and untreated particles in epoxy / filler systems, the first model can be characterized as corresponding to perfect adhesion quality between matrix and filler while the second one to low adhesion quality. The strength predicted by the first model is close to that of treated particles corresponding to high strength. This model corresponds to an upper bound of the strength in cube-within-cube models. The strength predicted by the second model is close to that of untreated particles corresponding to low strength, but this model does not correspond to a lower bound of the strength. The systems used for comparison were resin/iron and resin/glass beads particulate composites. For the case that adhesion exists between matrix and filler, the strengths predicted by the present models are in agreement to those provided by an existing evaluation method in the literature.

         

         

          SHEAR PROPERTIES OF LAMINATES MADE OF ISOTROPIC PCBA AND PMMA LAYERS AS DETERMINED THROUGH SHORT BEAM BENDING TESTS

         

        G.A. Papadopoulos, E. Sideridis and H. G. Papadopoulou

        Section of Mechanics, The National Technical University of Athens, 5 Heroes of Polytechnion Avenue, GR-157 73, Zografou, Athens, Greece.

        E-mail: gpad@central.ntua.gr 

        ABSTRACT 

        In this work shear properties of symmetric or asymmetric sandwich type laminated were obtained from the properties of the constituent laminae made of isottropic layers of Lexan (PCBA) and Plexiglas (PMMA). An investigation concerning mainly the influence of the stacking sequence of the laminate, which affect the mechanical properties was carried out. A brief theoretical analysis based on lamination theory and mechanics of materials was made in order to obtain some mechanical properties such as modulus of elasticity, deflection, etc. in order to compare with experimental results.

              Short beam bending tests with specimens made of sandwich type laminates made of various stacking sequences were performed. If multiple isotropic layers of various thickness are arranged symmetrically about the middle surface, from both a geometric and a material property standpoint, the resulting laminate does not exhibit coupling between bending and extension. However, some applications of laminated composite materials require asymmetric laminates to achieve design requirements. 

         

         

          EVALUATION OF THE ELASTIC MODULUS OF PARTICULATE COMPOSITES BY MEANS OF A SPHERE-WITHIN-CUBE AND A CIRCLE-INTO-SQUARE MODELS AND THE EFFECT OF FILLER SHAPE

         

        G. Bourkas, E. Sideridis, V. Kytopoulos, I.N. Prassianakis 

        National Technical University of Athens,Faculty of Applied Sciences, Department of Mechanics, Lab. of Strength and Materials, Zografou Campus, GR-157 73, Athens, Greece 

        ABSTRACT 

              In this paper the elastic modulus of particulate composites is evaluated, by means of two models, namely the sphere-within cube and the circle into square formations. The theoretical results predicted by the above representative volume elements are compared with formulae existing in the literature as well as with experimental results carried out through tension experiments and ultrasonic measurements in iron/epoxy particulate composites. The tensile experimental values of the elastic modulus (Ec) were found well below those of ultrasonic measurements. The theoretical values of Ec predicted by the first model are close to those of ultrasonic measurements for high filler volume fractions, while the respective ones predicted by the second model are close to those obtained from tensile experiments.

         

         

          DETERMINATION OF THE DYNAMIC MODULI OF PARTICULATE COMPOSITES BY MEANS OF THE BASIC THREE COMPONENTS MODELS IN CUBE-WITHIN-CUBE FORMATION

         

        G. Bourkas, V. Kytopoulos, E. Sideridis, C. Younis 

        National Technical University of Athens, Faculty of Applied Mathematical and Physical Sciences, Department of Mechanics, Laboratory of Testing and Masterials, Zografou Campus, GR – 15773, Athens, Greece 

        ABSTRACT 

        In this work, the dynamic elastic moduli of particulate composites are evaluated, by means of two models in cube-within-cube formation, each consisting of three components. For this purpose the correspondence principle is applied to the existing equations which provide the static elastic modulus of particulate composites, by means of these two models. Two general equations providing the storage and loss modulus respectively, of particulate composites which are valid for both models, are obtained. The theoretical results are compared with dynamic experimental results in iron / epoxy particulate composites as well as with existing formulae in the literature. Since the dynamic experiments and ultrasonic measurements have as a common parameter the frequency, an extrapolation of the storage modulus curves, predicted by dynamic experiments, is made as far as the respective values of ultrasonic measurements in iron / epoxy particulate composites. 

         

        Defect detection using capacitive imaging 

        G.G. Diamond and D.A. Hutchins 

        Univ of Warwick, School of Engin, Coventry,U.K.

        W. Mids, T. H. Gan, TWI Ltd, U.K  

          PREDICTION OF THE ELASTIC MODULUS OF PARTICULATE COMPOSITES BY MEANS OF A GENERAL EVALUATION METHOD USING A FOUR COMPONENTS MODEL

         

        G. Bourkas, C. Younis, B. Kytopoulos, E. Sideridis 

        National Technical University of Athens, Faculty of Applied Sciences, Department of Mechanics

        Lab. of Strength and Materials, Zografou Campus, GR-157 73, Athens, Greece 

        ABSTRACT 

              In this study, the elastic modulus of particulate composites by means of a model cube-within-cube is evaluated. The R.V.E. is consisted by four components, of which one component corresponds to the filler and the rest three conponents correspond to the matrix. Because of the different composite geometry in the three directions, 3 submodels are created, one in each direction, providing 3 different values for the elastic modulus. The evaluation procedure considers triaxial stress situation in each part of the model and the elastic modulus is evaluated by means of the governing stresses and elongations equations of the model. The theoretical results are compared with those derived by existing equations in the literature as well as with experimental tensile results and ultrasonic measurements in iron/epoxy particulate composites. 

         

         

         

          THE EFFECT OF INTERPHASE ON THE ELASTIC MODULUS OF PARTICULATE COMPOSITES USING TWO MODELS

          i) OF SIX and ii) OF SEVEN COMPONENTS

         

        E. Sideridis, G. Bourkas, V. Kitopoulos, J. Prasianakis, C. Younis 

        National Technical University of Athens,Faculty of Applied Mathematical and Physical Sciences, Department of Mechanics, Laboratory of Testing and Masterials, Zografou Campus, GR – 15773, Athens, Greece 

        ABSTRACT 

        In this paper the elastic modulus of particulate composites is evaluated by using two models: i) a six-component square-into-square model and ii) a seven-component cube-within-cube model. The R.V.E.s take into consideration the existence of the interphase between matrix and filler, which is a third phase in the composite whose thermomechanical properties vary between those of the inclusion and those of the matrix. The theoretical results are compared with those resulting by existing equations in the literature, as well as with tensile experimental results and ultrasonic measurements.


        1 Corresponding author;  Heroon Polytechniou 9, GR-157 73 Zografos, Athens, GREECE;

          email: badstrat@central.ntua.gr

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