Detection of Material Surface Cracks by Infrared Non-destructive Testing

When cracks exist on the surface of the material, there are various risks during the use of the specimen. Surface crack is also an important reason for specimen failure and damage. In this paper, the surface crack of the material is studied by using infrared thermal image microscope and adopting the passive infrared detection which is different from the traditional active infrared detection. The cracks in different directions and sizes were found by qualitative analysis of the chromium plated stainless steel. Because the cracks in the test block were too small and the contrast was not high, Matlab software was used for image processing to improve the contrast. The length of defects was detected by introducing a scale for quantitative analysis of the iron block. The error of the test results was analyzed, and a new test method to reduce the error was designed. The results of the two methods are compared and analyzed, which show that the passive infrared thermal imaging microscope has the ability to detect the size and shape of defects.