Application Of Anisotropy Lemaitre's Damage Criterion In Hot Power Backward Spinning Of Cast Aluminum Alloy Tube

7075 aluminum alloy has the characteristics of high strength,low density and corrosion resistance etc,it is widely used in the fields of aviation,space and automobiles.Hot power backward spin process has the advantages of eliminating casting defects,grain refinement,improve the performance of the organization,it has become one of the main methods for manufacturing thin-walled tube parts of brittle materials.However,due to the hard deformation of the cast 7075 aluminum alloy at room temperature and the poor fluidity of the material,it is very easy to crack during the spinning process that seriously affects the improvement of the quality of the workpiece.Therefore,an improved Lemaitre damage model is established in this paper and based on the ABAQUS finite element platform,a hot power backward spinning cracking model of the tube part is established,the cracking behavior during the spinning process of the tube part is systematically studied.The main contents and results of this paper are as follows:?1?The anisotropic behavior of plastic deformation of 7075 plate is experimentally studied,which are obtained the initial yield strengths(?₀,?_{4 5}and?₉₀)of 7075-T6aluminum alloy sheet,the anisotropy indices(₀r,r_{4 5}andr₉₀)and the six anisotropy coefficients a,b,c,f,g,h for the Barlat91 yield criterion.Then based on Barlat91anisotropic yield criterion and Lemaitre ductile damage criterion is improved,in the end,the anisotropic Lemaitre anisotropic ductile damage criterion considering the anisotropy of the material is established.?2?Based on the established Lemaitre anisotropic ductile damage criterion then the VUMAT heterosexual damage subroutines suitable for the ABAQUS application platform are developed that based on the Fortran language.To verify the established anisotropic damage criteria and the VUMAT subroutine,by using deep drawing method.And then based on the developed damage fracture subroutine,a prediction simulation model for multi pass strong thermal reverse spin damage and cracking of cast 7075aluminum alloy is established,and the reliability of the finite element simulation model is verified by the simulation.?3?The damage distribution of the workpiece during the spinning process is obtained through the established model.In the axial direction,the non-spinning area at the bottom of the workpiece has the least damage value compared with the other two areas,and the damage value in the central stable area changes greatly.In the circumferential direction,the damage value inside and outside the workpiece changes unevenly,that is,the workpiece damage is unevenly distributed.In these three directions,with the increase of spinning pass,the degree of damage inside and outside the workpiece tends to be consistent.?4?Taking damage and cracking as the research object,the optimum design of the forming process is carried out,and the optimum spinning process parameters are obtained through virtual orthogonal experiment.The optimal values of the feed rate,the speed of the mandrel,the friction between the mandrel and the workpiece,the friction between the roller and the workpiece,the temperature of the mandrel and the thinning value are obtained under different passes.