Pulsed inductive thermal wave radar (PI-TWR) using cross correlation matched filtering in eddy current thermography

Major problems in eddy current thermography include the compromise between depth dynamic range and resolution, the influence of surface emissivity variation and the low defect detectability. This paper presents pulsed inductive thermal wave radar (PI-TWR) by introducing the cross correlation (CC) matched-filtering in eddy current pulsed thermography (ECPT). CC phase and CC peak phase delay are used as characteristic features. The proposed method was verified through numerical and experimental studies, where steel sample and carbon fibre reinforced polymer (CFRP) sample were tested under transmission and reflection modes. The results illustrate a significant improvement in the dynamic range, depth resolution, emissivity variation reduction and detectability of subsurface defects and inside delamination for the nondestructive testing applications.