Deng Weilin, Kesari Haneesh
Brown University, School of Engineering, Providence, RI, 02912, USA.
Sci Rep. 2019 Feb 7;9(1):1639. doi: 10.1038/s41598-018-38212-z.
Contact force-indentation depth measurements in contact experiments involving compliant materials, such as polymers and gels, show a hysteresis loop whose size depends on the maximum indentation depth. This depth-dependent hysteresis (DDH) is not explained by classical contact mechanics theories and was believed to be due to effects such as material viscoelasticity, plasticity, surface polymer interdigitation, and moisture. It has been observed that the DDH energy loss initially increases and then decreases with roughness. A mechanics model based on the occurrence of adhesion and roughness related small-scale instabilities was presented by one of the authors for explaining DDH. However, that model only applies in the regime of infinitesimally small surface roughness, and consequently it does not capture the decrease in energy loss with surface roughness at the large roughness regime. We present a new mechanics model that applies in the regime of large surface roughness based on the Maugis-Dugdale theory of adhesive elastic contacts and Nayak's theory of rough surfaces. The model captures the trend of decreasing energy loss with increasing roughness. It also captures the experimentally observed dependencies of energy loss on the maximum indentation depth, and material and surface properties.
在涉及聚合物和凝胶等柔顺材料的接触实验中，接触力 - 压痕深度测量显示出一个滞后回线，其大小取决于最大压痕深度。这种与深度相关的滞后现象（DDH）无法用经典接触力学理论解释，并且被认为是由材料粘弹性、塑性、表面聚合物相互交错和水分等效应引起的。据观察，DDH能量损失最初随粗糙度增加而增加，然后随粗糙度增加而减小。其中一位作者提出了一个基于粘附和粗糙度相关的小尺度不稳定性发生的力学模型来解释DDH。然而，该模型仅适用于表面粗糙度极小的情况，因此它无法捕捉在大粗糙度情况下能量损失随表面粗糙度的减小。我们基于毛吉斯 - 达格代尔粘性弹性接触理论和纳亚克粗糙表面理论，提出了一个适用于大表面粗糙度情况的新力学模型。该模型捕捉到了能量损失随粗糙度增加而减小的趋势。它还捕捉到了实验观察到的能量损失对最大压痕深度、材料和表面性质的依赖性。
