超声振动珩磨表面残余应力数值模拟研究

目的磨削产生的残余应力对工件表面特性有重要影响,超声振动珩磨使磨粒具有极大的加速度而改变了材料去除机理,研究超声振动对工件表面残余应力的影响及产生机理。方法分析残余应力形成有限元理论,建立基于热弹塑性有限元法的超声振动单颗CBN磨粒切削40Cr Ni Mo A热力耦合有限元模型,并设置两次切削、卸载、约束转换及冷却等分析步。通过数值模拟得到不同振动参数下表面残余应力的分布情况,并对模拟结果进行分析。结果有限元计算得到的各分析阶段应力分布存在差别,超声振动参数设置达到仿真要求;对磨粒施加超声振动后珩磨力下降约26%,珩磨热降低约17%,切向残余压应力有所减小,垂直珩磨速度方向拉应力减小并向压应力转变。结论超声振动使珩磨力和珩磨热有一定程度降低从而改变了残余应力的分布及数值;振动频率在20 k Hz波动时对残余应力的影响不大;磨削速度减小,切向残余压应力增大,垂直磨削方向残余拉应力减小;振幅增大时,切向残余压应力减小,垂直方向残余应力增大。

Simulation Research on the Surface Residual Stress of Ultrasonic Vibration Honing

Objective To study the influence on residual stress as the grinding residual stress has important influence on workpiece surface characteristics and ultrasonic vibration honing makes the grains obtain a great acceleration which changes the material removal mechanism. Methods The residual stress finite element theory was analyzed, the coupled thermal-mechanical finite element model was established for the ultrasonic vibration honing of a single CBN grain cutting 40CrNiMoA based on the thermal elastic-plastic theory. Steps of two cutting processes, unloading, constraint transformation and the cooling analysis were set. The surface residual stress distribution was obtained by numerical simulation under different vibration parameters and the simulation results were analyzed. Results The stress distribution at each analytical step was different, the ultrasonic vibration met the requirements of the simulation experiment. The honing force decreased by about 26% and the honing heat decreased by about 17% when applying ultrasonic vibration, the tangential residual stress was reduced, and the residual stress at vertical grinding direction was also reduced and changed from the tensile stress to the compressive stress. Conclusion Ultrasonic vibration decreases the honing force and the honing heat which changes the distribution of residual stress and numerical values. The vibration frequency near 20 kHz has little influence on residual stress. The tangential compressive residual stress increases and the honing tensile residual stress at the vertical direction decreases with the decreased honing speed. The tangential residual stress decreases and the residual stress at the vertical direction increases with the increased amplitude.