We investigate the underlying tribological mechanisms and running-in process of a semi-crystalline polymer using molecular-dynamics simulations. We subject a slab of simulated polyvinyl alcohol to a sliding contact asperity resembling a friction force microscope tip. We study the viscoelastic response of the polymer to the sliding and show both plastic and elastic contributions to the deformation, with their relative strength dependent on the temperature. As expected, the elastic deformation penetrates deeper into the surface than the plastic deformation. Directly under the tip, the polymer has a tendency to co-axially align and form a layered structure. Over time, the plastic deformation on and near the surface builds up, the friction decreases, and the polymers in the top layer align with each other in the sliding direction (conditioning).

我们使用分子动力学模拟研究半结晶聚合物的潜在摩擦机理和磨合过程。我们使一块模拟聚乙烯醇经受类似于摩擦力显微镜尖端的滑动接触粗糙。我们研究了聚合物对滑动的粘弹性响应，并显示了塑性和弹性对变形的贡献，它们的相对强度取决于温度。正如预期的那样，弹性变形比塑性变形更深地渗透到表面中。在尖端的正下方，聚合物具有同轴排列并形成分层结构的趋势。随着时间的流逝，表面及其附近的塑性变形逐渐累积，摩擦力降低，顶层中的聚合物在滑动方向上相互对齐（调节）。