Research On Cold Extrusion Forming And Optimization Of Key Process Parameters Of Vehicle Spline Shaft

Vehicle spline shaft is a typical representative of vehicle power transmission parts,which has an essential application in-vehicle power transmission device and gearbox reverse device.It has the advantages of large contact areas,high bearing capacity,sound guidance,shallow tooth root,and small stress concentration.The spline shaft parts processed by cold extrusion technology not only have the characteristics of high production efficiency,high material utilization,and less subsequent processing procedures but also can form continuous fiber structure,effectively improving the mechanical properties of the spline shaft.However,there are some problems in cold extrusion forming of spline shaft,such as delicate filling of tooth shape and too large load,which limits the application and promotion of cold extrusion technology of vehicle spline shaft.In this paper,the spline shaft parts with the material of 20mncr5 are selected for systematic research.Firstly,three forming process schemes are drawn up by the cold extrusion method,and the three forming process schemes are tested by computer numerical simulation using the widely used professional finite element software DEFORM-3D.Then,the obtained forming load and the law of metal flow in the process of building defects change are observed and analyzed.Finally,process plan two is selected as a reasonable cold extrusion process plan.However,during the field trial production of method 2,there are still some forming defects such as short sufficient forming tooth length,insufficient filling of tooth top,angle collapse,pit at tooth bottom,and excessive load on the spline shaft for the vehicle.Because of the various forming problems still existing in-process plan 2,further numerical simulation process optimization tests are carried out.First of all,the orthogonal experiment and numerical simulation of new structure size design are combined to solve the problem that the forming tooth length does not meet the size requirements.Secondly,for the experimental analysis of forming defects such as insufficient filling of tooth top,too large load peak,and pit,the comprehensive orthogonal preliminary analysis of multi-objective function and multiple factors is adopted.The objective function is determined as sufficient tooth length,the radius of tooth top circle,peak forming load,and the key influencing factors are the angle of entering die ?,the height of working belt h,round corner R4 of die,etc.Finally,we use the climbing test to optimize the value range of factors further,and then use the optimized range to establish 15 groups of 3-factor-3-level CCD test scheme for the corresponding numerical simulation test.According to the test values,we get the nonlinear regression equation of the three optimization objectives.Furthermore,a group of optimized process parameters are obtained by multi-objective optimization of Design-Expert.Finally,the streamlined process parameters are applied to the trial production of the spline shaft parts,which reduces the forming load of the spline shaft,eliminates the forming defects,and improves the forming quality of the parts.