The Analytical Prediction of the Machined surface Characteristics and Their Improvement

提出了用有限元法预测加工产品特别是加工表面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，将几何非线性和不可压缩过约束松弛引入到有限切屑形成过程中。为了模拟流型切削过程从开始到稳定状态，还开发了刀具刃口前工件材料的特殊几何分离方法。通过仿真，分析得到了加工表面层内的残余应力应变分布。并预测了由于残余应力分布的重新排列而引起的工件从夹紧系统中释放后的变形。分析结果与实验结果进行了比较和讨论。为了改善表面特性，采用有限元模拟方法，研究了刀具前角和刀具前面摩擦特性对加工层内残余应力分布的影响。在锐刃刀具加工的顶面内，产生了切削方向的拉伸残余应力。刀具前倾角和摩擦特性对拉应力影响较大。侧翼面的法向应力对减小拉应力是有效的。通过控制刀具边缘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.