Research On Nondestructive Testing Method Of Part Crack Defect Based On Infrared Laser Excitation

Engines and other components in the aerospace field have a harsh working environment.During their service,they are prone to fatigue cracks,pits and other defects caused by reciprocating alternating stress and impact load,which greatly reduces the mechanical properties of the specimen.In order to carry out non-destructive testing of defective parts,this thesis studies a non-destructive testing method for cracks and defects of parts based on infrared laser excitation,and realizes non-destructive testing of mechanical parts.The main research contents of the thesis are as follows:First,a non-destructive testing simulation model of TC4 titanium alloy based on laser excitation is established.The flat-bottom hole defect is selected as the simulation specimen,the laser power is 100 W,the excitation time is 3s,and the simulation research is carried out.At the same time,an experimental laser excitation experiment was carried out,and multiple surface temperature values such as the excitation point and the defect center were selected as reference values to correct the simulation model.Secondly,based on the TC4 simulation model,carry out non-destructive testing simulation research.For flat-bottom hole defect specimens,vertical line crack defect specimens and inclined line crack defect specimens,parameters such as laser excitation time,laser power,defect depth and different inclination angles were changed to analyze the temperature change trend of the regions on both sides of the defect to reveal the defect The law of influence on the temperature distribution of the specimen;compare the temperature values ??on both sides of the defect,and analyze the temperature resistance effect of the defect.Finally,using the same parameters as the simulation model,the experimental study of TC4 titanium alloy was carried out.Under the laser excitation,the experimental detection of different defect specimens is carried out,and the consistency of the simulation results and the experimental results is verified according to the temperature distribution on the line connecting the defect center of the specimen and the excitation point.The fitting curve between the experimental parameters and the maximum temperature difference ΔTmax at the temperature measurement point is obtained by the method of data fitting,and the quantitative relationship between the experimental parameters and the maximum temperature difference value ΔTmax at the temperature measurement point is quantitatively analyzed.