Research On Magnesium Alloy Wheels Of Nearly Uniform Forming Technology By Expansion-closed Extrusion

With few natural resources and the increasingly strict requirements of environmentalprotection, lightweight become the inevitable trend of auto industry development. Magnesiumalloy is the best material equipped with a lightweight, in automotive applications canimprove the comfort and safety, and can realize energy conservation and emissions reduction.Wheel hub as an important part of a car, high comprehensive mechanical performancerequirements, however, magnesium alloy wheel hub fatigue performance difference isdifficult to meet the requirements become the bottleneck of restricting its application.Therefore, how to improve the magnesium alloy wheel hub fatigue performance become animportant task to the plastic forming technology research.In this paper, by using finite element numerical simulation method and test the extrusionforming process of magnesium alloy automobile wheel is studied.The main works havingbeen carried out are as follows：(1) Through the analysis of automobile wheel hub parts structure characteristics,combined with the deformation characteristics, magnesium alloy wheel expansion-closedextrusion forming process is put forward, the metal deformation process are analyzedtheoretically, and the results show that the expansion-closed extrusion which can get rid ofdifficult deformation zone obviously, also known as the high stress zone, extrusion stressrequired is reduced, the overall deformation more evenly.(2) Using finite element simulation software simufact for magnesium alloy wheeltraditional forming process and expanding-closed extrusion forming new technology for thedigital simulation, Two kinds of metal flow is studied in the process, stress and straindistribution and metal flow distribution, the results show that: the expansion-closed extrusion process can obviously improve the spoke of the equivalent strain, deformationuniformity is good; Traditional craft in spokes place metal streamline curve, straight arm partwith a small amount of streamline outcrop, and the expansion-closed extrusion processworkpiece metal streamline basic outline shape distribution along the wheel hub, streamlineshape is good, can satisfy the requirement of wheel hub to streamline.(3) Using simufact simulation software for expansion-closed extrusion forming underdifferent process parameters and billet size structure is simulated, and study the technologicalparameters of extrusion and the size of billet deformation uniformity and the influence law ofmetal flow line distribution, the results show that:(a) Mold temperature increase, extrusiontemperature and the overall temperature distribution is improved, reduce the flow stress andforming load, improved uniformity of deformation of the workpiece, good for improve thequality of extrusion, using isothermal extrusion, the workpiece deformation uniformity isgood;(b) When the velocity increasing, the uneven distribution of extrusion temperature andoverall degree increasing, equivalent stress increase is more obvious;(c) Improve thecoefficient of friction, can reduce the streamline outcrop defects, improve the extrusion flowform, but make the extrusion uneven distribution of equivalent strain rise;(d) The structure ofextrusion deformation uniformity and have effects on metal flow, inner diameter of hollowbillet sizes in the200mm when forming deformation uniformity and metal streamlinedistribution is better.(4) For magnesium alloy wheel expanding-closed extrusion forming process werestudied, and the forming parts was microstructure analysis and performance testing, theresults show that: the expansion-closed extrusion forming process wheel spokes partsobviously improve the mechanical properties, deformation uniformity is improved, theanisotropic basically eliminated, the fatigue life meet the use requirements, verify themagnesium alloy wheel hub the reliability of the expanding-closed extrusion formingprocess.