| The development trend of industrial manufacturing miniaturization poses new challenges to the joining process.It is of great significance to optimize the structural components of micro-components and enhance their application value by joining dissimilar metal materials with different performances.However,the difference in material properties such as plasticity,strength and elastic modulus of dissimilar metal materials restricts the stable implementation of existing micro-joining processes.Thus,it is urgent to develop the theory and process of micro-joining precision forming of dissimilar metal materials.Laser shock micro-clinching is a new joining process based on the principle of plastic forming combined with laser shock micro-forming.The process uses the shock wave effect of laser-induced explosive plasma to plastically deform the material to form a mechanical undercut structure.In this paper,the deformation mechanism of laser shock micro-clinching process is studied by numerical simulation method.The influence of process parameters on clinching process and results is analyzed.The experimental design and optimization method are used to obtain the best combination of process parameters.The characteristics of laser shock micro-clinching were analyzed,and the key techniques of numerical simulation such as shock wave pressure loading,material constitutive model establishment and solution time determination were solved.The numerical simulation model of laser shock micro-clinching was established,and the reliability of numerical simulation model was verified by experimental results.The dynamic response of the stress,strain and thickness of the foil in the numerical simulation results was analyzed.The temperature rise during the deformation process was studied.The results show that the forming process can be divided into three stages:axial bulging deformation,radial expansion deformation and forming the clinching undercut structure.The areas in which the thickness was severely reduced are the area in the upper plate that is in contact with the round corner area on the lower plate and the area in which the upper plate is in contact with the bottom plate.In the forming process,the temperature rise caused by shock wave propagation and plastic deformation is small.The effects of laser process parameters,material parameters and tooling structure parameters on the clinching process and results in the laser shock micro-clinching process were studied.The results show that the thickness distribution of the connected upper plate is mainly affected by the degree of deformation,regardless of the laser power density.Increased laser power density enables faster formation of clinching undercutting structures.The clinching result is best when the diameter of the laser spot is the same as the diameter of the pre-made hole of the lower plate.Selecting the appropriate thickness of the upper plate can improve the laser shock micro-clinching process to a certain extent.When the height of the spacer is 150?m,it is helpful to obtain a clinching joint with good forming quality.The matching relationship of the process parameters in the laser shock micro-clinching process is optimized by the optimization method.The results of orthogonal experimental design show that the number of laser shocks is a significant factor affecting the undercut value,and the spot diameter is a significant factor affecting the maximum thinning rate.Based on the central composite experimental design and response surface methodology,the response surface function model between the laser energy,the number of shocks and the spot diameter and the optirrized target was established.The genetic algorithm programmed by Matlab is used to optimize the response surface function model,and 32 non-inferior Pareto solution sets are obtained.The optimal satisfaction solution in the pareto solution set is found through the satisfaction function,and the optimization result are verified by the experiment. |
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