刀具磨损对于单点金刚石切削单晶硅的影响

Influence of Tool Wear on Cutting Mechanism of Single Point Diamond Turning of Silicon

单点金刚石切削(SPDT)是加工单晶硅最常用的方法,刀具磨损是影响加工表面或工件表面质量的重要因素,但是其中的磨损机制尚不清楚。为了研究刀具磨损对于切削机制的影响,本研究建立了单点金刚石切削单晶硅的分子动力学(MD)仿真模型。仿真结果表明随着刀具磨损程度的增加,切削力、表面损伤层厚度、位错分布面积、剪切变形和相变程度均增加。当使用已经磨损的刀具切削单晶硅时,挤压起主要作用,当使用未磨损刀具时,剪切变形起主要作用,工件表面损伤层主要是由硅的非晶相组成,使用磨损的刀具时产生的轴向力F t约是未磨损刀具的四倍。模拟结果同时表明使用未磨损金刚石刀具时会导致工件发生塑性变形,当刀具发生磨损后切削过程中会伴随有脆性断裂。

Single point diamond turning(SPDT)is the most commonly used method of processing monocrystalline silicon.Tool wear is an important factor affecting the machined surface or subsurface quality of workpiece while the wear mechanism is unclear.Molecular dynamics(MD)simulation model for SPDT of silicon was established to study the effect of tool wear on the cutting mechanism.Simulation results revealed that the cutting force,the surface damage layer thickness,the dislocation distribution area,the degree of shear deformation and phase change increase with the increase of tool wear.The squeeze effect plays a leading role when using a worn tool to machine single crystal silicon,while it is shearing deformation with unworn tool.Damaged layer on the machine surface is mainly comprised of amorphous phase of silicon.Thrust force F t with a worn tool is about four times higher than that with an unworn tool.Simulation results suggested that plastic deformation takes place when using new diamond tool,while it will be accompanied by brittle fracture with a worn tool.