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1

Characterization of material defects using active thermography and an artificial neural network

Dudzik S.

Metrology and Measurement Systems

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2013

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Vol. 20, nr 3

491--500

EN

In the paper a method using active thermography and a neural algorithm for material defect characterization is presented. Experimental investigations are conducted with the stepped heating method, so-called time-resolved infrared radiometry, for the test specimen made of a material with low thermal diffusivity. The results of the experimental investigations were used in simulations of artificial neural networks. Simulations are performed for three datasets representing three stages of the heating process occurring in the investigated sample. In this work, the simulation research aimed to determine the accuracy of defect depth estimation with the use of the mentioned algorithm is descibed.

2

Solution of Inverse Problems in Electromagnetic NDT Using Neural Networks

Ayad A., Benhamida F., Bendaoud A., Bihan Y. L., Bensetti M.

Przegląd Elektrotechniczny

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2011

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R. 87, nr 9a

330-333

EN

This paper presents a technique for solving inverse problems in electromagnetic nondestructive testing (NDT), using neural networks (NN). They are trained to approximate the mapping from the signal to the defect space. A crucial problem is signal inversion, wherein the defects profiles must be recovered from calculated signals by using finite element method (FEM), this method give good results by using the refinement mesh but in very long time. The idea of this paper is the exploitation of the FEM but with a middle mesh where the results are approached in short time. This signal was exploited in the inversion problem, where the maps represent the defects in the plate. The inversion results obtained with the NN are presented. The presented approach has permitted to realize good maps in a very reasonable training time with respect to others approaches.

PL

Przedstawiono metodę rozwiązania odwrotnego z wykorzystaniem sieci neuronowych stosowanego w defektoskopii. Sieć jest trenowana na podstawie próbek z defektami. Pozwala to na stosowanie metody FEM ze znacznie mniejszą liczbą oczek.

3

Two-level approach for solving the inverse problem of defects identification in Eddy Current Testing - type NDT

Putek P., Crevecoeur G., Slodička M., Gawrylczyk K. M., Van Keer R., Dupré L.

Archives of Electrical Engineering

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2011

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Vol. 60, nr 4

497-518

EN

This work deals with the inverse problem associated to 3D crack identification inside a conductive material using eddy current measurements. In order to accelerate the time-consuming direct optimization, the reconstruction is provided by the minimization of a last-square functional of the data-model misfit using space mapping (SM) methodology. This technique enables to shift the optimization burden from a time consuming and accurate model to the less precise but faster coarse surrogate model. In this work, the finite element method (FEM) is used as a fine model while the model based on the volume integral method (VIM) serves as a coarse model. The application of the proposed method to the shape reconstruction allows to shorten the evaluation time that is required to provide the proper parameter estimation of surface defects.

4

Use of pulse IR thermography for detection and quantitative description of subsurface defects in austenitic steel

Wysocka-Fotek O., Oliferuk W., Maj M.

Rudy i Metale Nieżelazne

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2009

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R. 54, nr 11

684-687

EN

Pulsed IR thermography is a non-destructive method that allows detection of subsurface defects in material. In this method the surface of the tested specimen is stimulated by heat pulse and its self-cooling process is analyzed. The temperature decrease rate is different for surface over defect with comparison to that over the sound material. It is caused by difference between values of heat diffusivity of defected zone and sound one. The purpose of this work is to determine the size and depth of the defects in austenitic steel on the basis of thermal contrast analysis. Because the thermal contrast is dependent on both these parameters, two independent experimental methods of defect size and depth determination were proposed.

PL

Termografia impulsowa jest nieniszczącą metodą badań, stosowaną do wykrywania defektów w warstwie podpowierzchniowej materiału. Polega ona na analizie rozkładu temperatury na powierzchni badanego materiału podczas jej stygnięcia po nagrzaniu impulsem cieplnym. Szybkość stygnięcia obszaru powierzchni nad defektem jest różna w porównaniu z szybkością stygnięcia powierzchni materiału jednorodnego. Jest to spowodowane różnicą pomiędzy wartościami dyfuzyjności cieplnej wymienionych obszarów. Celem pracy jest oszacowanie wielkości i głębokości defektu w stali austenitycznej na podstawie analizy kontrastu termicznego. Kontrast termiczny zależy od tych dwóch parametrów, dlatego w pracy zaproponowano dwie niezależne metody eksperymentalne ich szacowania.