Magnesium alloy inner ring bars are widely used in the fields of military industry,aviation and aerospace.Reasonable streamline distribution can not only enhance the strength of forgings,but also reduce the weight and improve the design limit.The traditional forming process of inner ring bars generally has some shortcomings such as low mechanical properties and poor bearing capacity of bars.The forward extrusion technique can improve the formability of the component and make the streamline of the inner ring bar intact.Based on rare earth magnesium alloy as the research material,the streamline distribution and the inner ring steel bearing capacity as the research target,by controlling the inner steel forming process on the basis of intensive parameter for structural optimization design,to optimize the die and the blank after the structure parameters of the influencing factors,and discuss its influence on the forming quality,and connecting with the product requirements to obtain the best experimental parameters.Finally,physical experiments are carried out to verify the results.The research content mainly includes the following aspects:(1)Analyzes the problems existing in the forming process of the inner ring reinforcement member and the unreasonable distribution of the metal streamline at the key part of the inner ring reinforcement root,and simulates the factors affecting the unreasonable metal streamline in the forming process by using the Deform-3D finite element simulation analysis software.(2)The distribution law of metal streamlines in the forming process of inner ring bars was analyzed by finite element simulation.The results show that the reasonable distribution of metal streamlines has a great relationship with the structural parameters of the die.Deform-3D finite element simulation software was used to analyze the metal flow rule in the forming process of the inner ring bar member.Taking the die structure parameters as the design variables,the equivalent strain and forming load as the objective function,the R-value optimization design of the die was carried out to obtain the best structural parameters of the die.According to these parameters,a set of reasonable extrusion forming die is designed.(3)The central composite design method(CCC)was used to complete the experimental design of forming parameters optimization.The three factors of rib root R value,rib thickness H value and extrusion speed V were selected as the design variables,and the equivalent strain S.D index was selected as the objective function.Through the surface response analysis and multi-objective optimization design,The optimal metal streamline distribution process parameters of the inner ring bead were obtained: the R value of the fillet corner at the root of the bead was 3mm,the thickness of the bead was 20 mm,and the extrusion speed was V=0.5mm/s.(4)On the basis of theoretical analysis and simulation,the extrusion experiments of inner ring bars were carried out,and the microstructure and mechanical properties were analyzed.The results show that the average tensile strength of inner ring bars with complete metal flow line is 294.83N/mm2,the average elongation is 9.8%,and the maximum normal stress is495 MPa.Compared with the traditional cutting process,it is increased by 18.1%,38.5% and150%,respectively.The advancement of extrusion process and the effectiveness of process parameter control are verified.Finally,through the bending experiment,the maximum bearing capacity of the inner ring bars with complete metal streamline is 12575 N,and the maximum bearing capacity of the inner ring bars obtained by the traditional cutting process is 10060 N.Through the above results,the performance of the inner ring bars formed by extrusion is better than that of the machined components.The main reason for the performance improvement is that in the forming process,the metal streamline of the inner ring bar member is complete and continuous,so that the bearing capacity of the root of the bar is improved.After forming and deformation,dynamic recrystallization occurs at the root of the metal,and the grain refinement is obvious.At the same time,there are also a large number of grain boundaries which hinder the grain growth and promote the grain refinement.The proportion of DRX reaches 56.1%,and almost half of the grains have been transformed into DRX grains.The whole alloy shows obvious bimodal texture,which can also bring strong mechanical properties. |