纳米切削过程中刀-屑接触区应力分布

Investigation on Stress Distribution along Tool/chip Interface in Atomistic Machining Processes

高速切削时刀屑接触区的应力分布直接影响切削过程、切削温度及刀具磨损。利用分子动力学技术对纳米切削过程中刀屑接触区的应力分布特征进行研究,分别采用EAM势、Tersoff势及Morse势计算单晶铜原子间、单晶硅原子间、工件原子与刀具原子间的相互作用力。分析纳米尺度下刀屑接触长度随切削距离变化的规律,探讨刀具前角对刀屑接触区应力分布的影响,通过描述刀屑接触区切屑原子的运动情况,为阐释刀屑接触区的应力分布特征提供依据。研究结果表明在刀-铜屑接触区,正应力在切削刃处最大,随着到切削刃距离的增大而减小,在刀-硅屑接触区,正应力以规则的波动形式逐渐减小。而切应力在切削刃处为负值,随着到切削刃距离的增大,切应力在刀屑接触长度的三分之二处增大到最大值后逐渐减小至零。

The cutting performance, cutting temperature and tool wear are influenced by the tool-chip stress distribution. The molecular dynamics simulation approach is performed to investigate the tool-chip stress distribution and friction phenomena in nano-machining of monocrystalline silicon and copper materials. Tersoff potential function is employed to model the inter-atomic force among silicon atoms, and EAM potential function is used to model the interatomic force between copper atoms, and Morse potential function is used to model the interatomic force between the workpiece atoms and cutting tool atoms. Both the relations between the contact lengths of tool-chip interface and the cutting distance, and the influence of the tool rake angle on the stress distributions are analyzed. The atom motion and interaction along the tool-chip interface are given to explain the stress distributions along tool-chip interface in the nano-machining process. The normal forces in copper exhibit a peak near the tool edge, and gradually decrease toward zero as the contact ceases to exist, while the normal forces in silicon present regular fluctuations along the tool-chip interface. The friction force in both copper and silicon all show a negative value near the cutting edge. After that, the friction force in copper reaches the maximum at a distance of two-thirds of the contact length and then gradually decreases to zero.