| As one of the important parts of the auto start-stop system,the unidirectional gear directly affects the comfort of the auto-start-stop system.At present,the cold extrusion forming method is widely used in the field of gear forming due to its high efficiency,low consumption,and environmental protection.However,the cold extrusion of gears has insufficient metal filling in the tooth profile area,too long tooth end forming collapse,phosphorus saponification lubrication method serious environmental pollution and friction models have a greater impact on the simulation results of gear forming.To solve the above problems,this subject proposes a micro-textured flow controlled cold extrusion method based on numerical simulation,carries out friction model research and gear forming experiments in gear forming simulation,and combined with laser surface micro-texture technology,solid lubrication technology and friction test to explore new cold extrusion lubrication treatment methods.First,use UG to establish a gear cold extrusion die model,and use DEFORM-3D to perform gear forming finite element simulation to analyze the existing forming defects;secondly,design pits,triangles,and groove micro-textures on the surface of the tooth-shaped die.The micro-texture flow control forming simulation with different topography is carried out to determine that the groove micro-texture flow control forming effect is the best,and the influence of the groove width,depth,density and angle on the gear forming performance is deeply studied.Based on the basic friction database obtained from the friction test,the pressure and speed-related friction model are fitted,and the simulation results of the traditional shear friction model are compared,and the accuracy of the friction model is verified through the gear forming test.Finally,research on the groove micro-texture laser processing technology was carried out to explore the influence of groove micro-texture parameters and graphene and polytetrafluoroethylene additives on the friction and wear properties of die steel surface.The main research conclusions are as follows:(1)In the gear cold extrusion simulation,the blank axial flow is dominant,and the blank radial flow in the tooth profile area is insufficient,resulting in low quality of the tooth formation and long collapse of the gear end face.(2)The micro-texture of pits,triangles and grooves can improve the radial flow state of the metal,and the gear collapse of the grooved micro-textured solution is reduced by 22.3%compared with the non-textured treatment solution.At the same time,as the groove width,depth,and density increase,the gear collapsed foot appears to decrease first and then increase,but it continues to increase with the increase of groove angle.The groove micro-texture with a width of 100μm,a depth of 20μm,a density of 30%,and an angle of 0° has the best flow control effect.The gear collapsed foot is only 3.03869 mm,which is 48.3% lower than the non-textured treatment solution.(3)The simulation results of the pressure and speed-related friction model established based on the friction database are better than the shear friction model,and the gear forming quality of the speed-related friction model is the best,which is the closest to the actual gear cold extrusion results,and the error of the gear foot length is only 9.4%.(4)The width and depth of the groove micro-texture increase with the increase of laser power and the number of repetitions,and decrease with the increase of scanning speed.(5)The friction coefficient of the textured die surface first decreases and then increases with the increase of groove width,depth,and density,and the current continues to increase with the increase of the angle.At the same time,the surface friction coefficient of textured die steel decreases first and then increases with the increase of graphene and polytetrafluoroethylene powder addition.Among them,the antifriction effect of graphene-containing lubricating oil is better than that of polytetrafluoroethylene. |
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