Research On Rectangular Micro Shear Clinching Of Metal Foils By Laser Shock Forming

In view of the micro joining requirements of the similar or dissimilar kinds of new lightweight metal foils in the manufacturing process of micro devices,this dissertation combines the advantages of multi-stage shear clinching and laser shock forming to propose rectangular micro shear clinching of metal foils by laser shock forming.The joining process provides a new micro joining method for similar or dissimilar metal foils.This dissertation studied the theoretical basis,basic process parameters,joint deformation process,process windows of similar or dissimilar metal foils,mechanical properties and failure modes of the joints,modeling and optimization on process parameters for the process.The main research work and achievements are as follows:Firstly,the formation of plasma in the interaction between laser and materials in the process was discussed.The simplified mathematical model of laser power density and laser induced shock wave peak pressure were determined.The pressurization effect of the soft punch and the impedance matching principle were investigated.The plastic deformation yield criteria under the complex load were introduced.The multi-stage shear clinching process was analyzed.The theoretical basis studies provided the foundation for subsequent experimental researches for the process.Secondly,the experiment system was built on Spitlight 2000 Nd-YAG laser.The experimental studies on the joint appearance and cross section were conducted to determine three basic process parameters.The soft punch thickness was 100 ?m,and the numbers of laser pulses on the upper and lower foil sides were respectively set as 2 and 1,which could facilitate joint deformation and process efficiency.The experiments determined the three stages of joint deformation,namely stage 1-drawing and shearing,stage 2-flattening,stage 3-restriking and fitting,and revealed the rule of joint deformation and thickness distribution in the process.The process windows of different process parameters including spacer thickness,laser energy for stage 1 and stage 2,and laser energy for stage 3 with total thickness of aluminum foil combinations were established.The mechanical properties and failure modes of aluminum foil combination joints were studied by single lap shearing test.It was found that the perpendicular shear force is always greater than the parallel shear force,and the perpendicular shear curve has greater load stiffness than the parallel shear curve.The parallel shear test has only one failure mode and the perpendicular shear test has four failure modes.In addition,experimental investigations on the combination of copper foil and aluminum foil,titanium foil and aluminum foil,stainless steel foil and aluminum foil metal foil showed that the process is also suitable for the micro joining of dissimilar metal foils.Their process windows,mechanical properties and failure modes were further studied.The above researches provided the foundation for further optimization of process parameters.Finally,the experiments based on single-factor method revealed the influence of voltage percentage of laser pulses on upper foil side,the voltage percentage of laser pulses on lower foil side,spacer thickness and the width of shearing molds on the joint deformation,and obtained reasonable optimization range of process parameters.The center composite design(CCD)method was used to acquire the four-factor five-level experimental design matrix and the responses were also obtained by experimental researches.Based on the response surface methodology(RSM),the mathematical models of two kinds of shear force were established,and the interaction effects of the four process parameters were studied by analysis of variance.Based on the maximum shear force optimization criterion,and the maximum shear force under the small power and joint size optimization criterion,the optimization results of the process parameters are obtained and verified by experiments.The predicted results of the models are in good agreement with the experimental results.It is found that the design and optimization model for rectangular micro shear clinching of metal foils by laser shock forming based on the response surface method is effective.This research proposed rectangular micro shear clinching of metal foils by laser shock forming providing a new process for micro joining of metal foils.The research of this paper provides the guidance for further industrial application of the process.