Infrared Thermal Wave Imaging For Identifing Different Subsurface Defects

For the demands of nondestructive evaluation (NDE) of kinds of materials, several samples were designed and produced, and the quantitative identification and measurement of the defects in materials were studied by using pulsed heating thermal wave imaging.According to typical subsurface defects in materials, metal and nonmetal samples with intentionally planted subsurface defects were simulated. And different experimental conditions were designed for the detection of the samples by using pulsed heating infrared thermal wave NDE. By analyzing the thermal wave theory and the experimental thermal curve which based on the thermal graph of the simulated samples, we proved that, the corresponding cooling curve of the area which has dissimilar interface will deflect from the cooling curve of the non-defective area through the ad hoc mode on the ad hoc time. The study of ascertaining the deflecting objective criterion, the deflecting time and the deflecting mode will help us determine the depth and quantitative identification of defects.The experimental result of the simulated samples proved that the subsurface defects identification algorithm can effectively identify different defects in stainless steel and plastic material, such as, water, oil, air and plasticene inclusion. And different slopes for the four kinds of defects in the stainless steel sample and black plastic sample are given. The algorithm of subsurface defects identification in materials can be extended to other kinds of defects in materials. And the corresponding program in VC++ will be a practical application software for the quantitative identification of defects.