Experiment And Simulation Analysis On Laser Peening Convex Forming Of 2024-T351 Aluminium Alloy Sheet

Laser peening forming is developed from the basis of cognition and research in the mechanism of laser shock processing.It is a new type of flexible precision forming method for sheet metal.In the process of laser shock peening,the high residual compressive stress field has generated in the workpiece surface is distributed along the thickness direction,which drives the plates bending deformation with smaller curvature.Based on this phenomenon,the concept of laser peening forming is gradually developed.Laser peening forming has remarkable advantages in the field of sheet metal forming:high grade deformation pressure?GPa?,high strain rate(10⁶¹0⁷s^-1),short duration,sheet metal forming without mould,laser parameters can be precisely controlled to predict the shape of sheet metal,so it is expected to replace the traditional mechanical shot peening forming.In addition,the residual compressive stress is retained on the surface after using laser peening forming technology,which can improve the plastic forming ability and other related mechanical properties of the material,and can effectively improve the performance of the metal parts.This paper takes 2024-T351 aluminum alloy as the research object,and carries on laser peening convex forming experiment and simulation analysis.The distribution of residual stress field in the deformation zone of the sheet is analyzed from the laser parameters,the impact routs and the thickness of the plate,and the bending angle of the plate is analyzed quantitatively after laser peen.A laser shock forming model was established by using ABAQUS finite element analysis software,and the distribution of the residual stress field and the deformation of the plate after forming were simulated and analyzed.The main research work and conclusions are as follows:?1?2024-T351 aluminum alloy sheet has good capability of laser peening forming.Different combinations of laser processing parameters?such as laser energy,impact frequency,etc.?and plate thickness will result in different bending deformation characteristics.In this experiment,the smaller thickness of the plate?1mm?shows a concave deformation under the larger laser energy?5J?,and the thickness of the plate?3mm?shows a convex deformation under the small laser energy?3J?.When the plate is concave deformation,the deformation of the sheet is proportional to the laser energy.But there is no definite correlation when the deformation of the sheet metal is convex.When the laser parameters are fixed,it is found that there is a thickness threshold,less than that is concave deformation,greater than that is convex deformation.?2?The distribution of residual stress field in the impact zone of 2mm thickness2024-T351 aluminum alloy plate after laser impact convex forming is analyzed,and the influence of the number of laser scanning times and the number of impact rows on the size and distribution of residual stress field after the sheet forming is obtained.The results show that residual compressive stress induced by laser peen increases with the increase of impact scanning times,and increases with the increase of laser energy.There is a certain residual compressive stress on the surface and back of the impact zone of the plate,and the residual stress value of the laser shock zone is larger than that in the unaffected zone,and the residual compressive stress of the impact surface is higher than the residual compressive stress value at the unimpacted surface of the back surface.?3?Combined with the experimental results,the simulation software ABAQUS is used to simulate the distribution of residual stress field and the process of plate deformation,the experimental results and simulation results of laser shock convex forming are compared and analyzed.The simulation results show that the simulation method can effectively predict the forming angle and residual stress field distribution of laser shock forming.