Precision Forming Process Analysis And Numerical Simulation Of Gear Shaft Parts

The gear shaft parts are studied in this paper,which are the key power transfer component of vehicle,and are widely used because of their smooth power transmission and precision.The tooth parts includes external teeth and internal teeth,the forming methods mainly include cutting machining,powder metallurgy and plastic forming.The material utilization is low for cutting machining.The cost is high and the precision is difficult to control for powder metallurgy,which can hardly meet the requirement.Cold extrusion forming is the major processing method of plastic forming,due to the stronger fatigue resistance of the devices made by cold extrusion forming,which keep metal fiber from being cut off in the forming process.Besides,the extrusion forming has the high material usage rate(85%-90%).However,the cold extrusion can lead to incomplete filling and superposition defects.To analyze the major processing parameters of cold extrusion forming are helpful to avoid the defects in manufacturing process.In this paper,two feasible forming schemes are determined by analysis of the cold extrusion of the gear shaft.Forming scheme I is combination of cold extrusion and machining,which is that outer teeth is made by the cold extrusion while internal teeth is made by the machining process.Forming scheme II(back pressure forming process),on the basis of the forming scheme I,is to control the flowing of metal by mold cavity,to obtain the metal parts with different shapes,sizes and mechanical properties,which is a one-time extrusion of internal and external teeth.Extrusion forming can ensure the metal fiber flow is not cut off.The cold hardening properties of the metal can be used to improve the strength of the formed parts,so that the bearing capacity,safety and service life of the parts could be improved.At the same time,a new type of cold extrusion die structuredesign with back pressure device is carried out in the forming scheme II(back pressure forming process).In this paper,two schemes of cold extrusion process for gear parts of vehicle are proposed.Two finite element models are establish and the numerical simulation are carried by the DEFORM-3D.The simulation results show that the equivalent stress,the equivalent strain,the damage value and the maximum forming load of the workpiece are all lower than the first one when adopting the scheme II(back pressure forming process)with the back pressure device,and the forming quality are better.Compare with scheme I,scheme II(back pressure forming process)can save 22% material,the forming load are only 86%of scheme I.Besides,the numerical simulation test on the extrusion forming of the gear shaft parts during the cold extrusion forming process are also carried out.Through the orthogonal experiment of numerical simulation analyses: punch velocity,friction coefficient,die entrance angle and punch guide angle of main cold extrusion forming process parameters on the extrusion load effect rule,and get the optimal combination of process parameters optimization of process parameters.The results show that the optimum forming speed are15mm/s,the friction coefficient is 0.05,the entrance angle of the cavity is 45° and the leading angle of the die is 1.5°.The simulation results of the combination show that the maximum forming load are 312 k N,which are reduced by 31.30% compare with 454 k N,the maximum forming load before optimization.Finally,the actual manufacturing process with the optimized process parameters are carried out.The tooth parts are filled completely,the shapes are uniform and defect-free,the accuracy of the gear shafts meet the requirements,which verify the reliability of the process,the optimized parameters and the simulation results.