纳米/超细晶切屑形成机理的有限元研究

Investigation into Formation Mechanism of Nano-Crystalline/Ultra-Fine Grained Chip via Finite Element Method

建立了大负前角和钝圆半径联合作用的大应变切削模型,采用有限元分析软件模拟较低切削速度下刀具前角和钝圆半径对切屑形态、等效应变、应力、应变速率、切削温度和主切削力的影响.结果显示,随着刀具前角的减小和钝圆半径的增加,切削变形区中的等效应变、应力、应变速率、切削温度和主切削力均有一定程度的增加,且刀具前角比钝圆半径影响更为显著;负前角切削时,钝圆半径的作用明显减弱;大负前角低速切削时,切屑在相对低的温度、较高的应变速率和应力下发生大剪切应变,形成具有纳米/超细晶结构和高硬度的切屑材料.

In this paper, first, a large-strain model describing the machining with large negeative rake angle and blunt round radius is established. Then, the effects of the tool rake angle and the blunt round radius on the chip shape, the effective strain and stress, the strain rate, the cutting temperature and the main cutting force during the cutting at a relatively low cutting speed are analyzed with the finite element software. The results indicate that （1） with the decrease in the tool rake angle and with the increase in the blunt round radius, the effective strain and stress, the strain rate, the cutting temperature and the main cutting force all increase, especially with the tool rake angle; （2） the effect of the blunt round radius weakens at a negative tool rake angle; and （3） large strains are imposed on the chip at a low temperature and a high stress and strain rate, which helps to produce nano-crystalline/ ultra-fine grained chip materials with high hardness by the cutting with large negative tool rake angle and low cutting speed.