Theoretical And Experimental Research On Residual Stress And Hardened Layer Of Hardened Gear Steel By Ultrasonic Vibration Grinding

Gears are key components of the transmission system that transmit motion and power.At present,the high-speed development of precision equipment such as high-speed vehicles,aerospace and new energy sources has increased the demand for transmission gears,and it has also raised high and even stringent requirements for its service performance and fatigue life.The residual stress of the gear surface and the quality of the hardened layer play an important role in the indicators of the anti-fatigue life.Therefore,a series of researches have been carried out to investigate the processing technology of high-performance gears in the past decades.Ultrasonic vibration assisted machining can effectively change the processing mechanism of traditional machinery due to its concentration of instantaneous energy,high frequency vibration impact and unique cutting mechanism.In this paper,the surface residual stress and the quality of the hardened layer are studied by considering the thermal-mechanical coupling effect of the hardened 42 CrMo gear steel under ultrasonic vibration grinding.Finally,an efficient and controllable processing method is provided for the anti-fatigue manufacture of high-performance gears.(1)Based on the trajectory characteristics of abrasive particles and the grinding mechanism of abrasive particles in ultrasonic vibration grinding process,the mathematical model of the ultrasonic vibration grinding force is established,and the temperature of the grinding zone under ultrasonic vibration grinding conditions was simulated and analyzed with ABAQUS finite element simulation software,and using the developed axial ultrasonic vibration test platform for test verification.The research shows that the ultrasonic vibration grinding changes the material removal mechanism and the heat dissipation mode.Compared with the traditional grinding,the grinding force is reduced by up to 38% in the ultrasonic vibration grinding and the grinding temperature is also reduced,which validates the theoretical analysis.(2)A three-dimensional finite element simulation model for ultrasonic vibration grinding of hardened gear steel was established using the thermo-mechanical coupling.The simulation of residual stress in grinding was realized and verified by experiments.The influence of different grinding parameters on residual stress during the process of ultrasonic vibration and traditional grinding was studied.The research shows that the residual compressive stress appears on the surface of the specimen,and the ultrasonic vibration processing contributes to the generation of residual compressive stress.The overall improvement is about 14% to 45%.The simulation results are in good agreement with the test results,which verify the reliability of the test.(3)The surface micro-morphology,surface roughness,and surface hardness of the hardened layer were studied.The results show that the hardened layer micro hardness of the surface is also significantly improved and micro crack propagation is controlled,the surface roughness is also significantly reduced,because of the ultrasonic vibration changes the material removal mechanism during the ultrasonic vibration grinding process.It is obvious that the test piece surface quality of ultrasonic vibration grinding is superior to the surface quality of the test piece under the traditional grinding conditions.