Methods for suppression of the effect of uneven surface emissivity of material in the moving mode of eddy current thermography

Uneven surface emissivity will cause illusory temperature variations in eddy current thermography, which has an adverse effect on defect detection. Although some methods have been proposed to eliminate the effect, they are not suitable for the moving mode of eddy current thermography. In this study, a hypothesis is proposed and based on this hypothesis two methods are put forward to remove the influence of uneven surface emissivity: (1) temperature gradient based method and (2) wavelet transform method. The experimental results show that the hypothesis is correct under certain conditions and the two methods can be used to suppress the effect of the uneven emissivity. The two methods can be applied to the moving mode of eddy current thermography. The defect information can be extracted from temperature fluctuations by using the two methods.