Research On Shock Forming Mechanism And Real-time Monitoring System Of Nanosecond Pulsed Laser

Laser shock forming technology uses high-energy ultra-short pulse laser to process materials.The pulsed laser is absorbed in a very short time to generate plasma.The plasma expansion and explosion induce shock waves to change the shape and internal mechanical properties of the material.In complex parts,small curvature bending,forming,Difficult forming and micro-part forming fields have unique advantages such as good controllability,high precision,and dimensional stability,and have good application prospects in aerospace,micro-electromechanical systems and other industries.Due to the extremely short loading time of shock waves,many coupling factors in the forming process,and the complex laser shock forming process,metal parts show different bending mechanisms.It is necessary to carry out further in-depth research on the laser shock forming mechanism and forming process.The paper developed a customized system for measuring deformation of laser shock forming based on digital profiler,tested the deformation law of 2024 aluminum alloy under Nd: YAG high-energy pulsed laser shock,and experimentally studied the concave-convex bending mechanism to characterize the mechanism of pulsed laser shock forming.The specific research content is as follows:1)Design and develop a real-time monitoring system to measure material deformation during laser shock.In order to improve the measurement accuracy of sample deformation in the laser shock forming process,a non-contact,high-precision ultrahigh-speed digital profiler was selected to build a laser shock-deformation real-time monitoring system based on the high-speed profiler.According to the deformation curve measurement requirements of the part impact forming,multiple modules such as real-time acquisition and offline measurement were designed,and a customized software system was developed to monitor the sample deformation process during the laser impact forming process,and successfully obtained the twodimensional and three-dimensional deformation data and curves of the part forming.The research results show that based on the measurement data of the real-time monitoring system,a variety of experimental schemes are proposed to improve the laser shock forming process,which can improve the accuracy of laser shock forming in practical applications.2)The experimental study of the concave-convex bending mechanism characterizes the laser shock deformation mechanism of 2024 aluminum alloy.The research results show that during the laser shock forming,keeping the values of other parameters constant,increasing the sample thickness will reduce the size of the sample deformation.When the sample thickness changes from 1mm to 3mm,the deformation mechanism transitions from a concave surface to a convex surface formation mechanism,and the transition interval is between 1.2mm and 1.6mm.The laser intensity and spot overlap rate are proportional to the magnitude of the deformation.The area impacted by the laser will also affect the deformation of the sample.When the laser impact area is large,the sample bends into a parabolic shape.As the laser impact area decreases,the sample bending gradually becomes "V-shaped".Increasing the laser intensity will increase the roughness of the processed sample,the increase of the sample thickness will reduce the roughness of the sample,and the increase of the spot overlap rate will reduce the roughness of the sample.The theoretical model and monitoring system of laser shock forming proposed in this paper realize the effective monitoring of material deformation process,and lay the foundation for the reasonable optimization of laser shock forming parameters and industrial application.