Research On Coating Thickness Measurment Based On Infrared Nondestructive Testing Technology

Under the premise of preserving the properties of the substrate material,the coating has the characteristics of increasing ability that are not belong to substrate,such as high temperature resistance,corrosion resistance and wear durable,is widely used in the aerospace,automobile,construction and other industries.Complex manufacturing process and terrible service environment makes the coating easy to produce thickness deviation,wear,cracks,debonding,porosity and other defects.Coating thickness is a significant indicator in coating design and service.Coating thickness has a serious impact on the coating’s key performance if it is too thin or too thick,which is the quality assurance of the coating that needs to be controlled.Due to the complex thermal properties of the coating structure,the current research on infrared non-destructive testing technology of coating thickness is still in its infancy.This dissertation starts with the continuous heat wave transmission mechanism in the coating structure,simulates and analyzes the coating structure under different conditions,constructs the continuous heat wave excitation infrared non-destructive testing platform,processes temperature signal filtering algorithm,and fits the filtered temperature signal,research coating thickness detection and other aspects of in-depth research based on continuous heat flow excitation.According to the theory of heat transfer,the heat flow transfer process inside the coating structure is analyzed,a two-dimensional temperature field model is constructed,and the relationship between the material or thickness and the surface temperature of the coating structure is determined.Based on the related knowledge of finite element method,the structure of the coating was simulated and calculated.By controlling the thickness of the coating,the thickness of the substrate,the coating material and the substrate material respectively,the factors affecting the trend of the temperature signal on the surface of the coating were analyzed to provide a theoretical basis for the experiment.The continuous heat flow excitation infrared non-destructive testing platform and the preparation of the specimen were established.The thermal image video stream was obtained through experiments.The original data is processed based on the Savitzky-Golay filtering algorithm and the Leave-One-Out Cross-Validation fitting.Respectively,based on the temperature curve of the coating thickness measurementmethod,based on k-range temperature rate of change of coating thickness detection method,based on k-range temperature change rate of intersection of the coating thickness detection method to extract the coating thickness-related characteristic information from temperature data.The accuracy of each method was tested separately,and finally the validity of the three methods was verified.