Infrared Nondestructive Testing Of GFRP Laminates And POD Analysis

Glass Fiber Reinforced Polymer/Plastic(also known as GFRP)is a combination of two kinds of non-metallic materials.Due to its excellent corrosion resistance and high temperature resistance,it can play a good heat insulation effect,which can be used for the preparation of heat insulation layer.At the same time,it plays a protective role in the internal matrix,and is widely used in the military and aerospace fields.Linear frequency modulation infrared thermal wave nondestructive testing(NDT)technology has many advantages,such as convenient detection,quick response,simple operation and wide detection range,which is superior to the traditional infrared nondestructive testing technology.In this paper,the linear frequency modulated infrared thermal wave NDT technology is used.The theoretical analysis of thermal wave conduction,numerical simulation,testing test and POD(probability of detection)detection probability are studied systematically..According to the basic theories of material science and heat transfer,the heat transfer equation is established.The excitation process of Chirp frequency modulated heat flow in GFRP laminates was numerically simulated.The influences of defect plane size,defect diameter-depth ratio,scanning period and CHIRP modulation frequency on the surface temperature field of GFRP specimens were studied,and the influences of different factors on the temperature difference were obtained.The first step of the test is to build a linear frequency modulated infrared thermal wave nondestructive testing system.The experimental data are processed by Discrete Fourier transform,fractional Fourier transform,Hough transform and corrosion expansion algorithm were used to process the image,and the SNR of the defect area was calculated.The influences of defect size,heat source power,scanning time and Chirp modulation parameters on the detection results were studied,and compared with the results of numerical simulation analysis.The results show that there is a slight deviation between the two results,and the influence law of parameters has no great change.The influence of test parameters and image algorithm on detection probability is studied.The Hit / Miss method is used to analyze the probability of faultiness check,.The response value and threshold value are calculated according to different divided areas.On this basis,the defects with different depth ratio are calculated;The obtained values were processed according to parameter estimation and normal distribution mathematical theory,and POD curves were drawn.The influences of heat source power,scanning time,initial frequency,termination frequency,defect determination threshold and different image algorithms on detection probability were analyzed,and the detection methods were evaluated.It lays a foundation for the quantitative nondestructive testing and the study of linear frequency modulation NDT.