Page 113 - 摩擦学学报2025年第9期

第 9 期 张伟鑫, 等: 机械受压工况下软-硬作用界面的接触行为研究 1367

model interface and in-situ observing the contact mechanic behavior. In view of the characteristics of bigger deformation
size, high speed of surface deformation and large surface energy dissipation of soft contact interface, the optical system
of the point contact was designed and built, in order to realize the observation and measurement of large-size
deformation area (contact diameter of mm order), and at the same time, it can track in situ in a very short time.
Considering the difficulty, variability and ethical issues in obtaining biological tissues, researchers generally choose
elastomers as models to carry out related basic research. Among them, cross-linked polydimethylsiloxane (hereinafter
referred to as PDMS) is widely used in biological simulations due to its mechanical properties similar to human tissue,
easy manufacturing, physiological inertness, low cost, and good thermal and oxidative stability surface. In this study, the
soft contact interface consists of a smooth hard ball and a transparent glass disc coated with an elastic soft cushion layer.
Firstly, a high-speed camera was used to record the entire deformation process, and then the acquired image sequence
was systematically analyzed to draw the change curves of the contact diameter and the indentation depth with time.The
measurement results showed that the contact diameter of the deformation area increased with the increase of load and
ranged from 1.01 to 2.21 mm. By comparing these curves of the measured value of contact radius α3 with the predicted
value of Hertzian contact theory, it was found that the Hertz contact model no longer accurately predicted the contact
radius, therefore a new contact theory model for soft-coated materials needed to be developed based on experimental
results, e.g. a modified Hertzian theory model. Simultaneous measurement of contact diameter with micron-level
accuracy and indentation depth with nanometer-level accuracy had been achieved during the mechanical loading,
holding load and unloading processes, the visual measurement of deformation occurring on soft contact surfaces both in
time and space had been realized. The change of the surface contact contour over time further described the entire
deformation process the mechanical response speed of the PDMS film along the normal load direction and in the radial
direction was inconsistent, and the former was faster. The results would like to contribute to the understanding of the
complex contact mechanical behavior of soft-hard interacting interfaces and the tribological performance and lubrication
mechanisms of soft material surfaces.
Key words: mechanical stress; soft-hard action interface; in situ optical measurements; dynamic contact; mechanical
deformation

生物体内存在众多湿滑软接触界面，其特殊的机 阻力. 随后，科学家们开展了一系列评价材料力学性
械应力耗散机制和典型的水合润滑特征，使得受压剪 能的试验研究 [8-13] ：对于偏硬的本体材料，常用的接触
切工况下组织器官之间几乎感觉不到疼痛. 然而，当 力学试验主要通过对样品进行拉伸和压缩测量等，根
这些湿滑界面处若发生磨损、降解和润滑失效时将会 据长度、厚度和接触面积的变化来评价材料的力学性
产生摩擦并引发生理病痛 ，例如，滑动的天然软骨发 能，例如弹性模量和屈服强度等. 然而，对于湿滑软材
[1]
生病变磨损将导致退行性关节炎 ，长时间佩戴隐形 料而言，例如关节软骨、水凝胶和隐形眼镜等，这些表
[2]
[3]
眼镜因润滑效果不佳将引起干眼病等 . 区别于传统 面多具有微孔状特征和软硬复合(甚至梯度化)特征，
的硬-硬接触界面，这类湿滑软接触界面的摩擦行为 施加外载荷时界面变形行为呈现出复杂力学行为，表
较为复杂，最具显著特征是接触区域的动态变形，受 现为发生了更大尺寸的变形量和变形速率，且宏观力
压剪切工况下的界面接触行为机制仍然不清楚，限制 学性能与材料的微观结构高度相关，例如厚度、孔隙
了高性能仿生润滑材料的研制. 与硬接触材料相比， 率、弹性模量和表界面特性等多种因素，难以用传统
柔软的生物材料表面承受相同载荷会发生更大的变 的力学接触理论来解释. 因此，开展软硬作用界面的
形，且本构关系变得更为复杂 [4-5] ，构建仿生软接触模 接触力学行为研究和实现接触过程的动态测量是1项
型界面和原位成像观测系统，研究机械受压工况下的 具有挑战性的工作.
动态接触行为，是理解软物质作用界面摩擦特性和润 近年来，成像技术的飞速发展架起了材料宏观力
滑机制的首要任务. 学性能和摩擦学特性与材料内在微观特征参数之间
接触力学问题始于1882年Hertz解决了2个弹性球 的桥梁，研究人员已经结合光学成像技术开展了软材
[6]
体间的接触问题 ，Hertz通过光学成像对玻璃半球和 料的变形和摩擦特性的若干基础研究工作 [14-23] ，例如
[14]
玻璃板之间牛顿环进行观察，当以已知速率施加载荷 Dunn等 利用原位粒子排阻显微镜技术(PEM)观察
时实现了界面接触面积和穿透深度的测量，并给出了 了聚丙烯酰胺探针(水凝胶球)与聚苯乙烯圆盘在受
[7]
理论解 ，并用于了解该特定界面处的磨损率和滑动 压作用下(加载速率约为0.36 μN/s)的界面接触行为，