Crack detection for metallic materials based on eddy-current pulsed-phase thermography

The surface and near surface crack of metallic materials can be detected efficiently and accurately by eddy current thermography. In this paper, combining with eddy current thermography and pulsed phase analysis, 45# steel with surface and subsurface cracks were studied by inductive heating simulation and experiments, which were aimed to solve the problem of the phase spectrum distribution and the influence of temperature distribution on the phase spectrum. It shows that, the phase spectrum distribution has nothing to do with temperature value, but is closely related to temperature trend. The phase image has good suppression to inhomogeneous heating, and can also broaden the detection range. Crack can be easily detected when frequency is below 12.5 Hz. The conclusions are experimentally verified, in order to provide guidance for quantitative crack detection with the phase information in the future study.