Theoretical Analysis And Experimental Research On Deformation Of Cantilever Sheet Induced By Laser Peening

As a novel surface strengthening technique, laser peening (LP) has a great application prospect in several industries, including aerospace, automotive, medical industry, etc. It has been proved that strong shock wave induced by pulse laser can make complex thin-walled parts deform and affect shape and dimension precision. The quality of strengthening should be guaranteed, and at the same time, the deformation needs to be controlled within the error range. Both of them are the imperative problem which should be solved. In this dissertation, the process of sheet bending deformation induced by laser shock has been studied and the main factors influencing the deformation have been discussed. In addition, the effect of the LP on the material was studied. The main research work is listed as follows:(1) Based on the Fabbro shock pressure model and impact dynamics, the analysis model of cantilever sheet deformation induce by laser impact was established. During the process of LP, laser loading history is extremely short and the sheet deformation in laser loading stage was ignored. The forming process was simplified into two stages and the deformation of two stages was analyzed and calculated. Selecting 2Cr13 stainless steel sheet as the shock object, accuracy of the analytical model was verified by the experiments.(2) Simulation model of laser shock cantilever plate was established. The deformation process of sheet was researched by using ABAQUS explicit dynamic analysis module. The key problems in the process of numerical simulation were concluded, and some influence factors on sheet metal deformation were discussed.(3) On the basis of theoretical analysis and numerical simulation, laser peening 2Cr13 stainless steel cantilever sheet was implemented and the effect of different process parameters on impact deformation was studied. The main influence rule of the factors, including the laser energy, pulse width, the material size etc., on the sheet deformation, have been illustrated on the basis of theory analysis, combined with simulation results and experimental results. The deformation of sheets can be predicted with these parameters. Moreover, the laser peening process parameters can be determined according to the deformation error range of the target material.(4) Influence of laser peening on 2Cr13 stainless steel sheet material surface morphology and mechanical properties was studied. The effect on the material surface residual stress and micro-hardness induced by laser peening with different power density and impact times were investigated. Combined experiments and numerical simulation, the residual stress field induced by laser peening with the square spot was studied.