Research On High Precision Forming Process And Characteristics Of Microstructure Induced By Laser Shock Imprinting

Laser shock imprinting,with the advantages of high precision,high efficiency and low cost,can induce controlled ultrahigh-strain rate forming of metal material by high energy plasma shock wave.At present,metal microstructures have a wide range of applications,including microelectronics,sensors,optical devices,and other fields,so the high-precision manufacturing technology of microstructures is one of the key research fields in manufacturing industry.Though combining experiment and numerical simulation methods,the paper systematically analyzed the microstructure forming micro-process and forming law induced by laser shock imprinting.Besides,the changes and reasons of the formed microstructures comprehensive properties were explored.Firstly,the generation,propagation and effect of plasma shock wave induced by laser were summarized.The theoretical model for laser shock imprinting was established,and the parameters in the shock process were quantified,which provides theoretical basis for the numerical simulation.The paper also analyzed the effect of material size effect and dynamic yield strength during microscale ultrahigh-strain rate deformation.The size effect mechanism on formed parts was analyzed for laser shock imprinting technology,and a method for estimating dynamic yield strength of materials under ultrahigh-strain rate was proposed.Secondly,the paper set up an experimental platform for laser shock imprinting.Though adjusting the experimental parameters,including the forming scale,laser pulse energy,material,and forming shape,the forming law of microstructures was explored.The influence rule of size effect and dynamic yield strength on the forming results was analyzed.Experiment results showed that laser shock imprinting could fabricate high precision microstructures with complex shapes on various materials by adjusting the experimental parameters.In addition,Filling Rate and Vertical Degree were defined as the measurement index of forming accuracy.By observing the cross-section characteristics of formed microstructures and analyzing the internal unit stress,the high precision forming micro-process was divided into three stages: elastic deformation,plastic stretching,and plastic compression,and the characteristics of each stage were analyzed one by one.Then,through the ABAQUS non-linear analysis platform,the simulation model of laser shock imprinting was established,the material model and loading mode were defined,and the internal parameters changes of the formed microstructures werecalculated.The internal stress distribution,cross-section stress,profile change,and material thickness change law of the formed microstructures in different parameters were analyzed.By analyzing the parameter changes of three stages in the process of high-precision microstructure forming,it was concluded that the high-precision microstructure forming is a process of material flow "filling" and "stacking".Finally,the paper designed a series of experiments to explore changes of the comprehensive properties of the formed microstructures,and compared the properties,including roughness,corrosion resistance,hardness,and high temperature stability,between the complete formed microstructures,the incomplete formed microstructures,and the original surface of the material.The reasons for the changes of microstructural properties were explained by analyzing the macro-stress effect and the micro-grain change.Experiment results shows that laser shock imprinting can effectively improve the comprehensive properties of microstructures,which technology with functions of "forming" and "strengthening".