Process And Mechanism Study On Laser Shock Progressive Forming Of Copper Foil

Laser shock micro-forming technology is a technique that utilizes laser-induced plasma shock wave pressure to dynamically plastically deform a material to obtain a desired microscopic geometry.Compared with the traditional micro plastic forming technology,laser shock micro-forming is a non-punch forming technology,which avoids the problems of difficulty in processing fine micro punches and poor neutrality.Moreover,the high strain rate plastic deformation characteristics make the technology have the advantages of fast forming speed and the good quality of formed parts,and thus have broad prospects for development in the field of micro-manufacturing.At present,the research on laser shock micro-forming technology is mainly focused on some basic processes such as micro-bulging,micro-bending and micro-punching.The position of the laser pulse on the workpiece is fixed,and the shape of the workpiece is also simple and small.However,there are not many studies on micro-parts with complex shapes and large forming areas,such as fuel electrode plates.Based on this,a new process is proposed in this paper,defined as the laser shock micro-progressive forming process.The micro-progressive forming process of laser shock is a multi-physics comprehensive process.There are many factors that affect the forming effect.In addition,the progressive forming process is relatively complex,and it is more difficult to study the forming law and mechanism of the laser shock micro-progressive forming.This article chose T2 copper foil as the experimental material,and used the method of combining simulation and experiment.We systematically studied the laser shock micro-progressive forming process,and analyzed the deformation and the characteristics of the laser shock micro-incremental forming process,and revealed the influence of different process parameters on the forming results.The key technologies for numerical modeling of laser shock micro-progressive process are solved,including the establishment of material constitutive model,the mechanical model of shock wave pressure,and the application of moving loads that are closely related to the process.We established a numerical model of laser shock micro-progressive forming and verified its reliability.The displacement,stress,strain and other changes of the micro-progressive forming of the copper foil by laser shock were analyzed.The deformation process and the thinning characteristics of the formed part were analyzed.The propagation of the stress wave in the axial and radial directions were analyzed and the attenuation characteristics of the stress wave were discussed.In addition,parameters such as laser energy,spot diameter,impact strategy,spot overlapping ratio,and mold structure were changed to analyze the differences of forming depth and forming angle of the foil along the shock direction and the differences of fluctuation values along the forming direction.On this basis,the comprehensive stamping performance of the copper foil under different process parameters were investigated.Based on numerical simulation,the best process conditions for mold-sticking are determined as:high laser energy local shock one time,a spot diameter of 2.5mm,a laser power density of 2.99GW·cm-2,a spot overlapping ratio of 60%,a die entrance fillet radius of 0.3mm and a die bottom fillet radius of 0.3mm.The influence of laser energy,spot overlapping ratio,foil thickness and grain size on the forming results were studied.The forming angle,thickness distribution and micro-hardness distribution of the formed parts were investigated.The research shows:With the increase of laser energy,the forming angle of the foil gradually decreases to the mold angle of 90° and the forming ability of the foil increases.With the gradual increase of the spot overlapping ratio,the foil becomes more and more flat and the forming angle gradually decreases.The flatness and the forming angle of the foil tend to be stable when the spot overlapping rate increases from 60%to 80%.After the laser shock micro-progressive forming,the micro-hardness of the formed part improves significantly,and it is consistent with the thickness reduction distribution.With the decrease of the thickness of the foil,the forming ability of the shaped part is better,and the forming angle reduces,and the thinning rate of the shaped part increases,and the micro-hardness improves.With the increase of the grain size,the forming ability of the shaped part increases,and forming angle reduces,and the thickness of the formed part reduces more severely,but the micro-hardness reduces due to the increase of the grain size.