The Analytical Prediction of the Machined surface Characteristics and Their Improvement

提出了用有限元方法预测已加工产品特别是已加工表面的力学状态的分析方法。由于流型切屑形成过程是大变形问题之一，在有限地层中引入了几何非线性和不可压缩过约束的松弛。为了模拟流体式刀具从开始到稳定的加工过程，还提出了刀具刃口前部的特殊几何分离方法。通过模拟，解析地得到了已加工表面层内的残余应力/应变分布。并预测了由于残馀应力分布的重新排列而导致的卡盘系统释放后的功的变形。为了改善刀具表面特性，基于有限元模拟方法，研究了刀具前倾角和刀具前刀面摩擦特性对加工亚层残余应力分布的影响。在用锋刃刀具加工的顶面内，产生了沿切削方向的残余拉应力。拉应力受刀具前倾角和摩擦特性的影响较大。后刀面上的法向应力对降低拉应力是有效的。通过控制刀具刃口几何形状和使用合适的切削液，可以控制残余应力及其分布，改善表面特性。

The analytical method to predict the mechanical state of machined product, especially machined surface, with FEM was proposed. As the flow type chip formation process is one of the large deformation problems, geometrical non-linearity and relaxation of over constraint of incompressibility were introduced into the finite formation. In order to simulate the flow type cutting process from its beginning to the steady state, special geometrical separation method of work material at the front of tool edge was also developed. Through the simulation, the residual stress/strain distribution within the machined surface layr were analytically obtained. The distortion of work after released from chucking system, caused by rearrangement of residual stress distribution, was also predicted. These analytical results were compared and discussed with the experimental ones.In order to improve the surface characteristics, the effect of tool rake angle and friction characteristics of tool rake face on residual stress distribution within machined sublayr was investigated based on FEM simulation method. Within the machined top surface by sharp edge tool, the tensile residual stress in the cutting direction was generated. The tensile stress was greatly affected by the tool rake angle and by the friction characteristics. The normal stress on the flank face is effective for decreasing the tensile stress. It may be possible to control the residual stress and its distribution and to improve the surface characteristics by the control of tool edge geometry and usage of suitable cutting fluid.