前角对单晶镍纳米加工影响的分子动力学仿真

应用分子动力学仿真研究了单晶镍的纳米加工过程.通过研究加工力的变化规律,发现加工初期加工力剧烈波动与工件中产生了较大体积的层错结构有关.采用不同前角的刀具进行了一系列加工仿真,结果表明:在刀具前角的增大过程中,加工力及前刀面与切屑之间的摩擦系数逐渐减小;由于前角的增大使刀具对切屑的推挤作用与切屑的整体弯曲减弱,切屑高度增加及切屑中完好的FCC原子比也逐渐增加;工件亚表面的缺陷原子数目逐渐减少,损伤深度也呈减小趋势.采用负前角加工时,工件亚表面损伤较严重,出现了层错四面体结构和LC位错;工件内部高温原子数随刀具前角的增大而逐渐减少,并且工件的温度分布以刀具圆角为中心向工件内部辐射.

Molecular Dynamics Simulating Effect of Rake Angle on Single Crystal Nickel Nanometric Machining

Molecular dynamics simulation was used to study the nanometric machining process of single crystal nickel. The change rule of cutting force showed that the violent fluctuation of cutting force at initial stage is closely related to the generation of large stacking faults. The cutting tools with different rake angles were applied to conduct a series of simulations， the results showed that cutting force and the friction coefficient between rake face and chip decrease gradually with the increase of rake angle. The push and overall bending of chip decrease， and the chip height and the perfect FCC atom ratio gradually increase due to the increase of rake angle. The defect atom number decreases， as well as the damage depth of workpiece subsurface. In the process of machining with negative rake angle tool， the subsurface damage of workpiece is more serious， and the stacking fault tetrahedral structure and the LC dislocation are generated in workpiece subsurface. Meanwhile， the number of high temperature atoms decrease with the increase of rake angle， and the temperature distribution of the workpiece radiates from the tool corner to the workpiece.