We present experimental and theoretical results for the surface topography of a plastically deformed metallic (aluminum) block. When a hard spherical body (here a steel-, silica glass- or silicon nitride ball) with a smooth surface is indented in a metal block with a nominally flat, but still rough, surface, a spherical-cup-like indentation result due to plastic flow. The surface roughness in the indented region is, however, not entirely flattened. The long wavelength (macroasperity) content of the roughness result from the roughness on the original (aluminum) surface, but now plastically deformed. The roughness at short length scale, in the plastically deformed macroasperity contact regions, result from the roughness on the hard ball, and from inhomogeneous plastic flow.
We model the contact mechanics using the boundary element method, combined with a simple numerical procedure to take into account the plastic flow. The theory can semi-quantitatively describe the modification of the roughness by the plastic flow. Since the fluid leakage of metallic seals in most cases is determined by the long wavelength roughness, we predict that the leakage can be estimated based on the elastoplastic contact mechanics model employed here.
The plastic deformations of surfaces of some glassy polymers is very different from what we observed for aluminum, which we attribute to strong work-hardening and to inhomogeneous plastic flow for the polymers. Thus the numerical procedure to account for the plastic flow proposed here cannot be applied to glassy polymers in general.
State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院兰州化学物理研究所固体润滑国家重点实验室）；Peter Grünberg Institute (PGI-1), Forschungszentrum Jülich（于利希研究中心彼得·格林伯格研究所（PGI-1））；MultiscaleConsulting（多尺度咨询公司）
Multiscale contact mechanics for elastoplastic contacts
Luleå University of Technology（吕勒奥理工大学）；Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences（中国科学院兰州化学物理研究所）；Peter Grünberg Institute (PGI-1), Forschungszentrum Jülich（于利希研究中心彼得·格林伯格研究所（PGI-1））；MultiscaleConsulting（多尺度咨询公司）
Probing the micromechanics of a multi-contact interface at the onset of frictional sliding
利用数字图像相关技术研究了粗糙弹性体与光滑玻璃表面多接触界面的微观力学行为。在初始滑动状态期间，即静态和滑动接触之间的过渡期间，监测面内弹性体变形。随着剪切载荷的增加，一个环形的滑动区域，在与中央坚持区域共存，被发现逐步侵入接触。从界面位移场，切向应力场可以使用数值反演程序进一步计算。这些局部力学测量被发现是正确的Cattaneo和Mindlin（CM）的模型捕获。然而，密切的比较显示显着的差异，在位移和应力场，反映了过度简化的假设下CM的情况。特别是，我们的光学测量使我们能够表现出一个弹塑性摩擦本构方程，不同的CM的模型中假设的刚塑性行为。该局部本构律涉及与粗糙度相关的长度尺度，与Bureau \textit{et al.} [Proc. R. Soc.London A \textbf{459}，2787（2003）]，从而将其有效性扩展到介观尺度。测量允许对光滑界面的初始滑动的Cattaneo和Mindlin（CM）经典模型进行首次定量测试。小的偏差被观察到，并解释为粗糙界面的有限顺应性的结果，这与Amontons的摩擦定律的行为，假设是有效的CM的模型中的本地。我们说明了这些测量实际上提供了一种方法，用于探测粗糙的界面，我们发现是弹塑性类型的流变学。
