基于滑—停—滑机理的锯齿形切屑高速成形分析

Analysis of High Speed Forming of Serrated Chip Based on Mechanism of Slip-Stay-Slip

高速车削时被切削材料以极高的应变速率产生连续的塑性变形,产生大量的切削热,在出现集中剪切滑移的情况下,产生了连续型带状锯齿形切屑。根据高速外圆车削中碳淬硬钢切屑试样的SEM照片和金相显微组织照片分析了锯齿形切屑周期性形成的变形机理。被切削材料的变形过程由普通的剪切滑移变形和集中剪切滑移变形组成,切屑沿前刀面的流出可细分为“滑—停—(再)滑”三个阶段。切削速度和材料硬度是决定切屑变形的两个主要影响因素。只要能够使材料应变率增加、致使切削温度升高的因素改变达到某种临界状态都能促成锯齿形切屑的形成,锯齿形切屑的形态随着切削用量的改变而变化。

As the high speed cutting proceeds, the cut material yields the continuously plastic deformation at a great strain rate, a large amount of cutting heat is generated, and the phenomenon of local shear slipping occurs, that brings on the coming into being of continuous ribbon serrated chips. In this article, by the aid of the scanning electron microscope （SEM） photographs and metallographic micrographs of the serrated chips, which were obtained by high speed turning the hardened steel, the mechanism of the deforming of serrated chip at periodicity is studied on. The deforming process of the cut material is comprised of the normal plastic shear deforming and the local shear slipping deformation, and the process of serrated chip＇ s flowing out along the tool rake face is divided in detail into three stages of slip and stay and slip （again）, And that cutting speed and material hardness are two main influential factors that determine chip deformation. Providing the cutting parameters haven been changed to the critical condition which can make material strain rate and cutting temperature increase to the extent that local shear slipping occurs in the cut material, that helps to bring on the forming of serrated chip, and with the variations of the cutting parameters, the shapes of serrated chips change.