利用分子动力学方法模拟了刚性金刚石压头在Ni单晶体上的滑动过程, 讨论了压入深度对 摩擦力的影响(压入深度对滑动过程中压头下方的微结构演化(能否发射位错环)有很大影响). 结 合摩擦过程中的塑性行为和能量耗散机制, 解释了产生摩擦力锯齿形曲线的原因, 证实了位错的形 核及湮灭是黏--滑机制的原因之一. 不同滑动速度对摩擦力影响的模拟表明, 压头的滑动速度决定 了压头下方位错环的运动和演化形式: 在高速滑动下, 形成的位错环依次沿着滑移面很快向Ni单晶 基体内扩展; 在低速滑动下, 压头下方产生的位错环互相发生作用, 在材料的亚表面形成较低能量的 大位错环, 由此产生的塑性变形主要集中在材料的亚表面.
The nano scratch process of a rigid diamond tip into Ni substrate has been studied by using molecular dynamcs simulation with EAM potential. Simulations are carried out to investigate the scratch depth effect on the friction force in the scrath process. Furthermore, microstructures around the tip are strongly depended on the scratch depth and dislocation loops can be formed with enough penetration depth. Also, present study reveals that stick-slip phenomenon results from dislocation emission and phonon dissipation. The sawtooth phenomena can be explained from the point that elastic energy stored in the stick process transforms to the dislocations beneath the tip, and then dissipates in the form of phonons, and finally forms the surface defects. Finally, effect of the sliding velocity is studied, which can be deduced from the simulation. The scratch velocity is the critical factor on the dislocation loop nucleation and evolution process. At the higher velocity, dislocation loop glide along slip lane downward to the bulk material. While at the lower velocity, dislocation loops beneath the tip will reaction with each other, and finnaly a large loop will be formed under the subsurface of the material. Plastic deformation will focus on the subsurface of the bulk material under low scratch velocity.
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