Abstract
The paper deals with eddy current non-destructive evaluation of partially conductive cracks. Especially, uncertainty of a depth estimation of such cracks from eddy current testing signals is considered here. A plate specimen having the electromagnetic parameters of a stainless steel SUS316L is inspected in this study by numerical means. A crack with variable depth, width and conductivity is positioned in the middle of the plate. One of the most utilized eddy current probes so called pancake probe is employed for the inspection. Response signals of the crack with different parameters are numerically calculated and further analysed. Presented results clearly demonstrate that the uncertainty of a crackdepth estimation considerably increases when conductive cracks are evaluated comparing to non-conductive cracks.
Highlights
Many structures require periodical inspection to keep safety, reliability as well as quality of various processes
Degradation detection of the construction material must be accompanied by interpretation of the measured data in order to estimate the extent of the degradation and predict future development thereof
The dependencies of the crack response signals are calculated for each crack in such b) dependences of the imaginary part on the real part of the detected signal with respect to the phase of exciting voltage
Summary
Many structures require periodical inspection to keep safety, reliability as well as quality of various processes. Degradation detection of the construction material must be accompanied by interpretation of the measured data in order to estimate the extent of the degradation and predict future development thereof. The damage tolerance approach includes four phases – detection, evaluation, analysis and prediction. In case a degradation of construction material is detected, the extent thereof is evaluated along with influence on the behaviour of the whole system and future development. One dimensional signal gained by scanning just above the crack along its length is taken as an input to the evaluation procedure. Three variables of the crack are estimated, i.e. a depth, a length and a position of its centre, while a profile, a width and the electromagnetic properties of the defect have to be adjusted in advance. The paper deals with evaluation of uncertainty in depth estimation of a detected partially conductive crack
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