Investigation On Three-dimensional Forming Of Metal Sheet With Multistep Laser Shock

Since the technology of laser shock forming(LSF)started up late,the relevant research literatures are quite limited at home and abroad.Its fundamental is to shape the metal sheet by utilizing a high-pressure shock wave induced by the interaction between the high-energy and short-pulse laser beam and the absorbing layer attached on the surface of the metal sheet.By controlling the relevant conditions such as laser pulse parameters,loading paths,die dimensions,etc.,the dimensions and accuracy of the deformed metal sheet can be controlled.So LSF technology has the advantages of good forming flexibility,high forming efficiency and simple mold required,and has a broad applications in the fields of aerospace,automobile,microelectronics,etc.In the present article,metal sheets with the material 2024-T351 aluminum alloy was employed,and the deformation processes of multistep LSF were researched.The main contents of the article are as follows:(1)Firstly,several metal sheet forming methods by utilizing laser beam as the processing tool were introduced,and their respective characteristics,fundamentals and distinctions were analyzed systematically.Then,the advantages of LSF technology as well as its development trend at home and abroad were explained in detail.Later,the LSF device and its main components including laser generator,absorption layer,confinement layer,and die were discussed in the respects of their characteristics,functions and selection.(2)The finite element model applied to LSF was established by using the finite element analysis software ABAQUS.Firstly,the formula of laser-induced shock wave pressure was estimated,and the usage of the formula was introduced by using the simulation of the onepoint and one-step LSF process as the research object.Then,some factors that will influence the deformed shape and the thickness distribution of the treated metal sheet such as the magnitude of shock wave pressure and the depth of die cavity were analyzed detailedly.The results show that the forming precision of metal sheet decreases with the increase of die cavity depth when the laser energy keeps constant,and increases with laser energy when the die cavities are the same.But the forming accuracy of metal sheet is limited because the plate will fracture when the laser energy exceeds a certain threshold.(3)On the basis of the study of the one-point and one-step LSF,a one-point and multistep LSF method was proposed in this paper.Firstly,the deformation processes of one-point and multistep LSF was analyzed.Then,dies with various cavities in depth applied in the first forming step was analyzed,and the predicted results were compared and discussed with that from the simulation of one-point and one-step LSF.The results show that,compared with the one-step LSF method,the multistep LSF measure can increase the forming limit and improve the forming precision of metal sheet.(4)In order to deform metal sheet with larger deformation area and deeper depth,a multipoint and multistep LSF method was proposed based on the previous analysis of onepoint and multistep LSF.And then,the deformation processes of metal sheet shocked by multipoint and multistep laser beam was predicted and discussed by using the finite element analysis software ABAQUS.The results show that with the method of multipoint and multistep LSF,the deformed area is larger and the forming precision is higher.