纳米多晶铜单点金刚石切削亚表层损伤机理

基于Poisson-Voronoi和Monte Carlo方法构建了多晶铜分子动力学模型，研究了纳米切削中多晶铜材料去除、切削力变化及晶界与位错间的相互转化机制。研究结果表明：晶界的阻碍作用使得切屑流向发生了改变，并在已加工表面形成凹槽和毛刺；切削过程中晶界前方材料变形能的逐渐积聚及晶界的最终断裂，造成了切削力发生由最大峰值到最小谷值的大幅波动；晶界附近的材料去除经历了材料变形积聚、位错穿越晶界、晶界转变为位错及晶界最终断裂等过程。通过详细分析多晶铜纳米切削中位错与晶界间的演化过程，揭示了晶界与位错间的相互转化机制，丰富了多晶铜亚表层损伤机理的内涵。

Subsurface Damage Mechanism of Nano Polycrystalline Coppers in Single Point Diamond Turning

Based on the Poisson-Voronoi and Monte Carlo methods, the nano polycrystalline copper molecular dynamics model of polycrystalline coppers was constructed. The material removal, change of cutting forces and the reciprocal transformation mechanism between grain boundary and dislocation were studied in nano-cutting. The research results show that the chip flow direction is changed under the hinder actions of grain boundary, and the burrs and cutting grooves are formed on the machined surface. There are several large fluctuations from maximum peak to minimum trough in the vibrational curves of cutting forces, which are caused by deformation energy accumulation and grain boundary fracture. The material removal process near grain boundary is undergone deformation accumulation, dislocation crossing the grain boundary, grain boundary transition into dislocation and grain boundary fracture. By analyzing the evolution processes between grain boundary and dislocation defect in detail, the mechanism of “grain-boundary-dislocation” reciprocal transformation in polycrystalline coppers is drawn out, which enriches the connotation of subsurface damage mechanism of polycrystalline coppers.