两种不同形状压头与单晶铜基体间接触力和摩擦力的纳观分析

在考虑单晶铜基体弹塑性形变和晶体各向异性情况下,基于原子尺度,采用混合势函数(EAM和Morse)和Verlet算法动态模拟了半球形和圆锥形两种不同形状压头与单晶铜基体的黏着接触和滑动摩擦过程,分析了接触力和摩擦力对单晶铜基体内失效原子变化情况.研究表明:当压头下压位移为0.9 nm时,由于半球形压头比圆锥形压头底部表面积大,导致半球形压头与基体之间的引力更大而更易产生黏着接触现象.在下压接触过程中,与半球形压头相接触的基体内出现位错原子长大成位错环,而与圆锥形压头相接触的基体未出现此位错环现象,但位错原子数均随压深的增加而增多;在滑动过程中,因半球形压头对基体的摩擦力和法向力比圆锥形压头对基体的摩擦力和法向力大,使得半球形压头比圆锥形压头正前方堆积的位错原子数多,但均随滑动距离的增加而增多.

Analysis of the Contact and Friction Force Behaviour between Different Indenter Shape and Substrate on Atomic Scale

On the conditions of considering the substrate elastic-plastic deformation and anisotropy of single crystal copper,the adhesive contact and frictional process of indenter (semi-spherical and conical) to the substrate were investigated by molecular dynamics simulation based on embedded atom potentials and verlet algorithm,and analyzed the influence of the contact and friction force on the failure of atoms in substrate. During the semi-spherical indenter moved down to 0.9 nm,the gravity between semi-spherical indenter and substrate became more lager than conical indenter,which resulted in the adhesive contact phenomenon happened easier than conical indenter because of the semi-spherical indenter's surface area is lager than conical indenter. At the same time,the dislocation loop grouped up and expanded as indentation depth increased for semi-spherical indenter in the indenting process,but not for conical indenter. During the process of sliding,the atoms ahead of the indenter accumulated gradually for the large friction and normal force of the semi-spherical indenter to the substrate,and the number of accumulated atoms in the above process is much larger than the atoms caused by conical indenter. Furthermore,because of the existence of adhesion and surface force,the number of residual atoms on the surface of the substrate contacted with a conical indenter is smaller than the one contacted with a semi-spherical indenter.