Automated characterisation of subsurface defects by active IR thermographic testing - Discussion of step heating duration and defect depth determination

The paper deals with two aspects of the automatic processing of thermograms visualising the front surface of object with internal defects. The material examination is done with active thermography. To assess the duration of step heating of the material tested and estimate the defect depth the 1D analytical model of temperature rising of the material surface was involved. Its applicability was examined by comparing temperature rises in time with those obtained for a 3D numerical model of material with hidden subsurface defect. Furthermore, method was validated with real measuring data. The conclusions are limited to the case of step heating.