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Title: Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses

Abstract

An eddy current testing (ECT) system with multi-coil type probes is applied to size up cracks fabricated on austenite stainless plates. We have developed muti-channel ECT system to produce data as digital images. The probes consist of transmit-receive type sensors as elements to classify crack directions, working as two scan direction modes simultaneously. Template matching applied to the ECT images determines regions of interest in sizing up cracks. Finite element based inversion sizes up the crack depth from the measured ECT signal. The present paper demonstrates this approach for fatigue crack and stress corrosion cracking.

Authors:
; ;  [1]; ; ;  [2]
  1. Institute of Fluid Science, Tohoku University, Katahira 2-1-1, Aoba-ku, Sendai (Japan)
  2. Power and Industrial Systems, R and D Laboratory, Hitachi, Ltd., Hitachi, Ibaraki (Japan)
Publication Date:
OSTI Identifier:
20798264
Resource Type:
Journal Article
Resource Relation:
Journal Name: AIP Conference Proceedings; Journal Volume: 820; Journal Issue: 1; Conference: Conference on review of progress in quantitative nondestructive evaluation, Brunswick, ME (United States), 31 Jul - 5 Aug 2005; Other Information: DOI: 10.1063/1.2184598; (c) 2006 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
36 MATERIALS SCIENCE; AUSTENITE; AUSTENITIC STEELS; CRACKS; EDDY CURRENT TESTING; FATIGUE; FINITE ELEMENT METHOD; IMAGE PROCESSING; STRESS CORROSION

Citation Formats

Endo, H., Uchimoto, T., Takagi, T., Nishimizu, A., Koike, M., and Matsui, T. Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses. United States: N. p., 2006. Web. doi:10.1063/1.2184598.
Endo, H., Uchimoto, T., Takagi, T., Nishimizu, A., Koike, M., & Matsui, T. Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses. United States. doi:10.1063/1.2184598.
Endo, H., Uchimoto, T., Takagi, T., Nishimizu, A., Koike, M., and Matsui, T. Mon . "Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses". United States. doi:10.1063/1.2184598.
@article{osti_20798264,
title = {Natural Crack Sizing Based on Eddy Current Image and Electromagnetic Field Analyses},
author = {Endo, H. and Uchimoto, T. and Takagi, T. and Nishimizu, A. and Koike, M. and Matsui, T.},
abstractNote = {An eddy current testing (ECT) system with multi-coil type probes is applied to size up cracks fabricated on austenite stainless plates. We have developed muti-channel ECT system to produce data as digital images. The probes consist of transmit-receive type sensors as elements to classify crack directions, working as two scan direction modes simultaneously. Template matching applied to the ECT images determines regions of interest in sizing up cracks. Finite element based inversion sizes up the crack depth from the measured ECT signal. The present paper demonstrates this approach for fatigue crack and stress corrosion cracking.},
doi = {10.1063/1.2184598},
journal = {AIP Conference Proceedings},
number = 1,
volume = 820,
place = {United States},
year = {Mon Mar 06 00:00:00 EST 2006},
month = {Mon Mar 06 00:00:00 EST 2006}
}
  • The eddy current field perturbation due to a thin crack may be described as the field generated by a current dipole layer located on the surface of the crack. In this paper the spatial Fourier-transform of the eddy current field Induced by a known dipole layer Is evaluated analytically It the dipole layer density function Is given as, for example, a Taylor`s or Fourier series. This result Is used for the calculation of the impedance change of the exciting coil due to a crack by solving an Integral equation. In the case of an unknown crack the measured Impedance Ismore » used for reconstruction. By zeroth order optimization the shape of the crack is varied to fit the calculated Impedance data to the measured ones. Several local minima of the objective function are found and statistically processed to give reliable approximation of the crack shape even in the case of sparse and noisy data.« less
  • This paper deals with the electromagnetic nondestructive testing performed by SQUID magnetometry on stratified aluminum alloy plates as those commonly encountered in the aircraft industry. The anomalous magnetic fields generated by flaws wit h known electromagnetic characteristics have been modeled by a three-dimensional specific code based on a finite element formulation. The numerical solution has correctly predicted the shape of the complicated magnetic field response due to the defect. Once accuracy and reliability of experimental data taken by superconductive probe have been tested, a benchmark-like problem has been faced. Measurements performed by conventional probes like fluxgate and inductive coil havemore » been compared with the ones taken by innovative device based on superconductive materials.« less
  • A new three-dimensional (3-D) finite element scheme for eddy-current nondestructive evaluation (NDE) problems is described that calculates directly the perturbation of the electromagnetic field due to defects in metallic specimens. The computational costs of such problems are usually very high using available finite element schemes, and the new scheme is supposed to lower these costs. The basic concept, the direct calculation of the field distortion due to the flaw, is provided for rather general defects, but the detailed finite element scheme is discussed for zero-conductivity flaws. The source terms of the formulation are determined from the unperturbed field, and themore » impedance change due to a defect can be calculated as an integral over the flaw. A finite element scheme for solving problems with crack-type defects is also presented as a limiting case of the formulation for zero-conductivity flaws. Solutions of a benchmark problem from the testing electromagnetic analysis methods (TEAM) workshop series (problem number 15/2) and of tube problems with artificial slots are presented and compared to experimental data.« less
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