Research On Quantitative Detection Of Defect Depth Through Reflection Method And Transmission Method Of Infrared Thermal Imaging Technology

After years of research and development, infrared thermal imaging nondestructive testing technology gradually matures. With a large detection area, inspection in-service easily, non-contact detection, safety and convenience and many other advantages, infrared thermal imaging nondestructive testing technology is widely used. Currently, the focus of development of the technology has been changed from evaluation and diagnoses of defects to the quantitative measurement of defects. However, the accurate measurement of defects depth remains difficult. This paper will study that the quantitative measurement of defects by reflection and transmission methods of infrared thermal imaging.A physical model to detect the buried depth by infrared thermal imaging detection technology was established, and the method of quantitative detection of defects was derived according to the heat conduction theory.The experiments of reflection method and transmission method of infrared thermal imaging detection on PVC specimens which contain chutes were conducted. The effects of the sampling point size and the defect width on the temperature field of the surface of the specimens was analyzed through the experimental data to guide the settings of sampling area of data processing, and detect the buried depth of the defects. And the influence of the motivation time on the measurement accuracy was analyzed.The simulate experiments of the groove defects inspection by reflection method and transmission method were conducted by the software of ANSYS, the effects of defects width and buried depth on simulation results and the effects of the motivation time on measurement of the buried depth of defects were analyzed.The results show that both the reflection method and transmission method can achieve the detection of defects and quantitative measurement of the defects depth. As to the nearly surface defects, in the same measurement accuracy, the motivation time of transmission method is shorter, the data processing is easier, and the defect detection is faster. As to the deeper defects, in addition to the advantages of the faster detection, the transmission method has higher accuracy.