Molecular Dynamics Analysis of Mechanical Surface Generation Process at Atomistic Level

为了了解金属微细加工中的切屑去除和表面形成机理，并寻求最终的加工精度，提出了一种基于分子动力学(MD)计算机模拟的可行性研究。分子动力学模拟是准确分析刀具刃口周围材料原子化行为的有效方法，由于刀具刃口的犁削作用，在刀具-工件界面附近的工件上相继产生大量位错。他们中的一些人进入剪切带并从自由面消失。由于位错的相继产生和消失，切屑似乎被稳定地去除。在刀具刃口下方穿透到工件内部的其他位错由于刀具刃口通过后工件的回弹而向后移动，并最终从工件表面消失。松弛的结果是，在工作表面上形成原子台阶。The Hight…在微细加工中，加工表面上剩余的多个步骤可以被认为是可达到的最终表面粗糙度。除了机床性能之外，有两个主要因素影响微细加工可达到的最终精度。一种是最小切屑厚度(MTC)，它是在切削刃上稳定地从工作面上去除的最小未切屑厚度。另一种是将刀具刃口轮廓传递到工作表面的保真度，与最终表面粗糙度处于同一水平。分子动力学模拟表明，微切削铜的MTC和传递保真度分别为刀具刃口半径的1/20~1/10，约为1 nm，约为1.0 nm。在铝的切割中，估算出较大的MTC和传递保真度，分别为1/10到1/5和2.0 nm。通过引入一种考虑电子传导的导热系数“标度”，可以合理地分析微切削中的切割温度。较少

To understand the chip removal and surface generation mechanisms and for the quest of ultimate accuracy attainable in micromachining of metals, a feasibility study is proposed based on molecular dynamics (MD) computer simulation. MD simulation is confirmed to be a useful method to analyze accurately the atomistic behavior of the workmaterial around the cutting edge in cutting process.Due to plowing of the cutting edge, many dislocations are generated successively in the workpiece near the tool-workpiece interface. Some of them move into the shear zone and disappear from the free surface. As a result of succesive generation and disappearance of the dislocations, the chip seems to be removed stably. The other dislocations penetrated into the workpiece beneath the cutting edge move back and finally disappear from the worksurface due to spring back of the workpiece after the passage of the cutting edge. As a result of the relaxation, atomistic steps are formed on the worksurface. The hight … More of the steps remaining on the worksurface can be considered as the ultimate surface roughness attainable in microcutting.Apart from machine tool performance, there are two primary factors affecting the ultimate accuracy attainable in micromachining. One is the minimum thickness of cut (MTC), which is the minimum uncut chip thickness stably removed from a worksurface at a cutting edge. The other is transfer fidelity of the cutting edge profile to the worksurface, which is of the same level as the ultimate surface roughness. MD simulations show that MTC and transfer fidelity in microcutting of copper is 1/20 to 1/10 of the radius of the cutting edge, that is about 1 nm for a realistic diamond cutting tool, and about 1.0 nm, respectively. In cutting of aluminum, a larger MTC and transfer fidelity, which are 1/10 to 1/5 and 2.0 nm, are estimated.By the introduction of a kind of "scaling" in thermal conductivity for which electron conduction is to be taken into account, the cutting temperature in microcutting can be reasonably analyzed. Less