Theoretical And Process Research On Cold Forming Metal Sheets Through Laser Shock

During the manufacturing or maintenance of the metal sheet parts,such as the aircraft skin,automobile body,thin-walled container etc,there are so many occasions needing the technology of curvature adjustment.As an emerging metal forming technology,laser shock forming has been widely researched by scholars because of its advantages of non-contact,no mold,high flexibility and cold processing.And there will be beneficial residual compressive stress on the surface of materials after laser shock to extend the service life of materials.In this paper,the theory and experiment prove that this technology can also be used in the adjusting the shape of metal materials.And we took 6061-T6 aluninum alloy as the research object,the related technical rules were studied,and the main mechanism of laser shock cold forming was studied through theoretical simulation.The main work and conclusions are as follows:(1)Numerical simulation study on the dynamic process of laser shock cold forming.ABAQUS finite element simulation software was used as the platform.The influence of different process parameters of laser shock cold forming,such as laser energy,shock area,coverage rate and the initial shape of sheet were investigated.The results show that when the laser-induced shock wave act on the convex surface of curved sheet metal,the deformation can be obtained in two ways by controlling the laser parameters.And the deformation is mainly influenced by laser energy,when laser energy is small,curved sheet will be more curved and when the laser energy is larger,the curved sheet will tend to be more flat.After the laser shock cold forming,the deformation of the curved target will become lager with the increase of the laser shock area or increase the coverage rate,but changing the laser shock area or the coverage rate will not change the deformation mode of the curved sheet.The initial shape of the sheet will also affect the laser shock cold forming,which is mainly determined by the angle of irradiation direction of the laser beam with the target surface.(2)Experimental study on the technical rules of laser shock cold forming has been conducted.The influence of laser energy,laser shock area,coverage rate and initial shape of sheet on laser shock forming of curved 6061-T6 aluminum alloy sheet were studied experimentally.Under this rule,straightening is achieved successfully.The results show that the experimental rules of laser shock cold forming is basically consistent with that of simulation.The deformation mode changes from lager curvature to smaller curvature with the increase of energy.Increasing the laser shock area or increasing the coverage rate will increase the deformation.Using this technology,the straightening of the curved plate is achieved successfully.(3)Study on the mechanism of laser shock cold forming.Two mechanisms of laser shock cold forming were studied through finite element simulation software ABAQUS.The research shows that:there are two mechanisms of laser shock cold forming:the stress gradient mechanism(SGM)and the shock bending mechanism(SBM).When the laser energy is small,the peak pressure of the laser-induced shock wave is small,and only a shallow plastic deformation area is formed on the surface of the plate to induce the stress gradient.The curved plate will be deformed in the way of larger curvature with the release of the stress gradient.When the laser energy is large,the peak pressure of the laser-induced shock wave is large and directly "penetrates" the curved plate.The moment of inertia under laser loading will make the curvature of the curved plate become smaller.The mechanisms will also have the coupling effect,the dominant one will determine how deformation of curved plate.