Detection And Experimental Study Of Coating Structure Through Pulsed Infrared Thermal Wave Testing Technology

Functional coating materials are widely applied in the environment of high temperatureand high heat flux because of their advantage of high strength at high temperature, etc. Toprevent the serious results caused by the damage at high temperature, it is necessary to takedetections during service. Pulsed infrared thermal wave nondestructive testing technology hasthe unique advantage of high excitation speed, etc., especially its application in comparativelysmooth thin plate component is better than the conventional detection methods.This thesis focuses on the application of the pulsed infrared thermal wave nondestructivetesting technology in testing functional coating materials specimen, and researchessystematically on theory and simulation and experiment. Firstly, thermal wave transfersmechanism in the coating structure has been studied according to the heat conduction theory,analytical model of the temperature field of coating structure containing defects, the analyticrelationships between surface temperature difference of defect and non-defect region andinternal defects characteristics in the coating have been ascertained. Secondly,three-dimensional discrete temperature distribution model has been set up and simulationanalysis has been carried on, influences of pulse width, sampling frequency, pulse strength,coating thickness, defect size and depth on the specimen have been researched. Finally, apulsed infrared thermal wave nondestructive testing system has been established and an imagesequence processing software including database has been developed, which is then used tomake quantitative analysis on the image sequences of prefabricated high temperature alloycoating and graphite coating test specimen.As the research result shows, this theoretical model can instruct the simulation andexperiment, the heat flow transfer effecting process in which is consistent. The optimumtesting parameters are obtained by comparing the theory, simulation and testing results. Thetemperature difference, the polynomial fitting coefficient difference and Fourier transformcharacteristic difference can be used as the evaluating indicator in the defect judgment.Especially wavelet analysis can be applied to the pulse detection, which can get a bettertreatment effect. Furthermore, there is a very close tolerance between the calculated data andthe actual data in the process of quantitative analyses.