Dagdeviren Omur E
Department of Physics, McGill University, Montréal, Québec, H3A 2TA, Canada. Department of Mechanical Engineering and Materials Science, Yale University, New Haven, CT 06511, United States of America.
Nanotechnology. 2018 Aug 3;29(31):315704. doi: 10.1088/1361-6528/aac43b. Epub 2018 May 14.
The effect of surface disorder, load, and velocity on friction between a single asperity contact and a model surface is explored with one-dimensional and two-dimensional Prandtl-Tomlinson (PT) models. We show that there are fundamental physical differences between the predictions of one-dimensional and two-dimensional models. The one-dimensional model estimates a monotonic increase in friction and energy dissipation with load, velocity, and surface disorder. However, a two-dimensional PT model, which is expected to approximate a tip-sample system more realistically, reveals a non-monotonic trend, i.e. friction is inert to surface disorder and roughness in wearless friction regime. The two-dimensional model discloses that the surface disorder starts to dominate the friction and energy dissipation when the tip and the sample interact predominantly deep into the repulsive regime. Our numerical calculations address that tracking the minimum energy path and the slip-stick motion are two competing effects that determine the load, velocity, and surface disorder dependence of friction. In the two-dimensional model, the single asperity can follow the minimum energy path in wearless regime; however, with increasing load and sliding velocity, the slip-stick movement dominates the dynamic motion and results in an increase in friction by impeding tracing the minimum energy path. Contrary to the two-dimensional model, when the one-dimensional PT model is employed, the single asperity cannot escape to the minimum energy minimum due to constraint motion and reveals only a trivial dependence of friction on load, velocity, and surface disorder. Our computational analyses clarify the physical differences between the predictions of the one-dimensional and two-dimensional models and open new avenues for disordered surfaces for low energy dissipation applications in wearless friction regime.
利用一维和二维普朗特 - 汤姆林森（PT）模型，探讨了表面无序、负载和速度对单个粗糙接触与模型表面之间摩擦力的影响。我们表明，一维模型和二维模型的预测存在基本的物理差异。一维模型估计摩擦力和能量耗散随负载、速度和表面无序单调增加。然而，二维PT模型有望更真实地近似针尖 - 样品系统，它揭示了一种非单调趋势，即在无磨损摩擦 regime中，摩擦力对表面无序和粗糙度不敏感。二维模型表明，当针尖和样品在排斥 regime中主要深入相互作用时，表面无序开始主导摩擦力和能量耗散。我们的数值计算表明，跟踪最小能量路径和滑 - 粘运动是两种相互竞争的效应，它们决定了摩擦力对负载、速度和表面无序的依赖性。在二维模型中，单个粗糙在无磨损 regime中可以遵循最小能量路径；然而，随着负载和滑动速度的增加，滑 - 粘运动主导动态运动，并通过阻碍跟踪最小能量路径导致摩擦力增加。与二维模型相反，当使用一维PT模型时，单个粗糙由于约束运动无法逃到最小能量最小值，并且仅显示出摩擦力对负载、速度和表面无序的微不足道的依赖性。我们的计算分析阐明了一维模型和二维模型预测之间的物理差异，并为无磨损摩擦 regime中低能量耗散应用的无序表面开辟了新途径。
