Research On Defect Recognition Technology Of Stealthy Materials Based On Laser Shear Speckle Interference

Stealth performance plays a crucial role in the combat capabilities and defense capabilities of modern fighters,while the performance of stealth materials and the coating of stealth materials play a key role in stealth performance.Among them,the stealth multi-layer material coating process is complicated and the thickness is thin,during the production,maintenance,spraying and flight of the aircraft,the stealth coating is susceptible to factors such as human factors,process level and flight environment,which cause the stealth material to fall off damage such as stickiness and cracks,which affects the stealth performance of the fighter.In particular,the debonding damage of the multi-layer heterogeneous stealth coating is difficult to detect because of its location specificity and the thickness limitation of the stealth material.Therefore,in order to improve the reliability of the stealth performance of the fighter,it is very necessary to carry out the detection and identification of the stealth coating debonding defects.Debonding defects are generated inside stealth materials,which are highly concealed,harmful,and difficult to detect.Infrared thermal imaging and ultrasonic testing have limitations,which can't detect debonding defects.Laser shear speckle interference technology is a large-area,non-contact optical measurement technology.When the stealth material containing the debonding defect is hot-loaded,the debonding defect area will cause an abnormal strain distribution on the surface of the stealth material.We need to collect two speckle interference images before and after the deformation of the stealth material and make a difference to obtain a fringe image characterizing the abnormal deformation.By identifying and locating the abnormal fringes of the speckle interference fringe image,the debonding defect information of the stealth material can be obtained.The main work of the article are as follows:1.This article deeply studies the speckle theory and the principle of laser shearing interference technology to detect defects,and establishes a mathematical model of the debonding defects of stealth materials.This article builds a Michelson laser shear speckle interference defect detection platform.The influence of the distance between each component in the defect detection platform on the speckle interference image was studied,and on this basis,the defect detection platform was optimized and improved.This article designs phase shift drive system and image display and processing software platform.This article formulates the defect experiment detection scheme.2.In this article we conduct an experimental test on stealth materials and obtain a speckle interference image;analyze the causes and characteristics of noise,and propose a four time phase shift algorithm to extract phase information and an adaptive median filter algorithm for noise reduction;adopt Contrast-limited adaptive histogram equalization(Contrast-limited adaptive histogram equalization,CLAHE)algorithm improves the contrast of speckle interference images;grayscale enhancement algorithm is used to improve image clarity;and edge detection algorithm is used to extract the fringe edges of speckle interference images.3.This article deeply studies the principle of defect identification YOLO algorithm;in view of the defect identification error of this algorithm,a non-maximal suppression algorithm(Non-maximal suppression,NMS)suppression error is proposed;a defect identification scheme is determined.We conducted defect detection and identification experiments on stealth materials containing debonding defects.The results show that the YOLO algorithm achieves the identification and positioning of speckle interference image defects.