Decay time analysis in pulse thermography

Abstract

Pulse Thermography is being used since several years for rapid detection of subsurface defects. This method is well suited for industrial applications because no physical contact to the test object is needed. Within a short measurement time robust results are obtained. Besides phase evaluation the decay time of surface temperature can be analyzed. In this paper the idea was to investigate the temperature half-life period of each surface point. The sample is assumed to be composed of small elements having the same surface area but different lengths. In a simple model, heat propagation in between these elements is neglected (local one dimensional model). Only changes in mass, heat capacity, and volume are considered. If the material has homogeneous thermal properties, the length (e.g. thickness) has a strong impact on the cooling down process. The concept takes the decay time for each element as a parameter for imaging.