Nano-scale machining of polycrystalline coppers - effects of grain size and machining parameters.
Nano-scale machining of polycrystalline coppers - effects of grain size and machining parameters.
复制标题
DOI：
10.1186/1556-276x-8-500
复制
发表时间：
2013-11-22
影响因子：
--
通讯作者：
Yang X
中科院分区：
文献类型：
--
作者：
Shi J;Wang Y;Yang X
在这项研究中，多晶铜结构的纳米级加工进行了全面的调查分子动力学（MD）模拟。模拟的情况下，构建研究晶粒尺寸的影响，以及各种加工参数。产生六种多晶铜结构，其具有分别为5.32、6.70、8.44、13.40、14.75和16.88 nm的对应等效晶粒尺寸。还考虑了切削深度、加工速度和刀具前角的三个水平。结果表明，随着切削深度的增加、切削速度的提高以及负前角的使用，纳米多晶切削需要更大的切削力。等效应力的分布与切削力的变化趋势一致。此外，还发现在5.32 ~ 14.75 nm的晶粒尺寸范围内，纳米结构铜的切削力和等效应力随晶粒尺寸的增大而增大，但晶粒尺寸增大后，切削力和等效应力有保留的趋势。这一发现证实了在多晶加工中存在规则的Hall-Petch关系和逆Hall-Petch关系，并且阈值晶粒尺寸的存在允许两个关系中的一个成为主导。位错-晶界的相互作用表明，晶界对位错运动的阻力是Hall-Petch关系的根本机制，而晶界的扩散和运动则是Hall-Petch关系的逆机制。
In this study, a comprehensive investigation on nano-scale machining of polycrystalline copper structures is carried out by molecular dynamics (MD) simulation. Simulation cases are constructed to study the impacts of grain size, as well as various machining parameters. Six polycrystalline copper structures are produced, which have the corresponding equivalent grain sizes of 5.32, 6.70, 8.44, 13.40, 14.75, and 16.88 nm, respectively. Three levels of depth of cut, machining speed, and tool rake angle are also considered. The results show that greater cutting forces are required in nano-scale polycrystalline machining with the increase of depth of cut, machining speed, and the use of the negative tool rake angles. The distributions of equivalent stress are consistent with the cutting force trends. Moreover, it is discovered that in the grain size range of 5.32 to 14.75 nm, the cutting forces and equivalent stress increase with the increase of grain size for the nano-structured copper, while the trends reserve after the grain size becomes even higher. This discovery confirms the existence of both the regular Hall–Petch relation and the inverse Hall–Petch relation in polycrystalline machining, and the existence of a threshold grain size allows one of the two relations to become dominant. The dislocation-grain boundary interaction shows that the resistance of the grain boundary to dislocation movement is the fundamental mechanism of the Hall–Petch relation, while grain boundary diffusion and movement is the reason of the inverse Hall–Petch relation.