平面磨削时表层质量过程监测参数的实验研究(2)——磨削表层应力状态的过程监测和预报

Experimental Study on In-Process Monitoring of Surface Quality during Surface Grinding(2)—In-Process Monitoring to Estimate the Surface Residual Stress

磨削表面残余应力状态是影响许多机器零件使用性能的重要表面特性之一。但它极难在磨削过程中进行监测和判断。 在平面磨床上进行大量16MoCr5表面硬化钢的磨削试验证明,磨削表面残余应力σ_Ⅱ与单位面积磨削功率P″_c及磨削力比F_n/F_t间存在很好的函数对应关系,在实验数据的基础上应用回归分析的方法建立了用过程特征参量计算表面残余测定仪应力的实验公式。当P″_c:未超过第二临界值P″_(cⅡ)时,用残余应力模型所计算的数值与由X射线应力测定仪测定的数值相符合。而在超过该临界值P″_(cⅡ)的情况下,由于磨削烧伤引起表面产生二次淬硬层其至裂纹,这时计算所得的高的拉应力值不就能在工件表面测得。 综合本研究课题的第一部分及本文的结果表明,单位面积磨削功率P″_c和磨削力比F_n/F可以作为磨削过程监测和预报表层质量的可靠的过程特征参量应用于生产实践。

The residual stress state of ground surfaces is one of the important surface properties that influence the functional behaviour of machine parts and highly loaded components. But it is very difficult to monitor in grinding process.Experimental results of surface ground casehardened 16MnCr5 yield a close relationship between the residual stress σn, the related grinding power Pc' and the grinding force ratio Fn/Ft. An equation based on experimental data is set up to determine the residual stress state from process quantities with the aid of regression methods. The calcuated residual stresses correspond satisfactorily with X-ray measured experimental results, if the related grinding power Pc' does not exceed a specific threshold PcⅡ' . In case of exceeding this value the calculated high tensile stresses cannot be measured on the workpiece surface due to grinding burn with newhardened layer and even cracks. The first part of this study [6] and this paper indicate that the related grinding power Pc' and the grinding force ratio Fn/Ft can be used as reliable characteristic quantities for in-process monitoring to estimate the surface quality in production.