稳定滑动时接触软表面的动态力测量：固定深度摩擦学
Dynamical force measurements for contacting soft surfaces upon steady sliding: Fixed-depth tribology
AI总结：
本研究通过固定深度摩擦学实验测量软表面滑动时的动态力，验证了摩擦力与速度的非单调关系符合Stribeck图，并发现粘滑模式的起始速度和位置随实验渐变，还通过球形样品实验关联了颗粒间摩擦与颗粒流动。
摘要：
表面间的摩擦学特性会对机械系统的响应产生深远影响，例如颗粒被驱动流动的方式。在本研究中，我们开展了实验，对浸没在流体中的两个半圆柱形PDMS（聚二甲基硅氧烷）样品在一系列受控速度下相互滑动时的切向力和法向力分量进行时间分辨测量。时间平均摩擦力在四个数量级的滑动速度范围内呈现非单调依赖关系，这与典型的Stribeck图及与之相关的三个动力学区域一致。我们专门设计的固定深度实验装置使我们能够研究力的波动情况，这种波动在其中一个区域表现出强烈的粘滑模式。重复实验的数据表明，粘滑模式的“起始速度”及其沿样品的空间位置在实验过程中均逐渐变化，表明样品表面发生了改变。此外，我们还使用球形样品相互摩擦开展了对照实验，以将颗粒间摩擦学与我们之前发表在《Physical Review Letters》126卷128001页（2021年）的工作中报道的颗粒流动建立直接联系。
英文摘要：
The tribology between surfaces can have a profound impact on the response of a mechanical system, such as how granular particles are driven to flow. In this work, we perform experiments that time-resolve the tangential and normal components of the force between two semi-cylindrical PDMS (polydimethylsiloxane) samples immersed in fluid, as they slide against each other in a range of controlled speeds. The time-averaged friction force shows a non-monotonic dependence on the sliding speed over four decades, which is consistent to the paradigmatic Stribeck diagram and three dynamical regimes associated with it. Our specially designed fixed-depth setup allows us to study the fluctuation of force that exhibits strong stick-slip patterns in one of the regimes. Data from repetitive experiments reveal that both the "onset speed" for the stick-slip patterns and its spatial location along the sample change gradually during the course of our experiments, indicating changes on the sample surfaces. In addition, we conduct counterpart experiments by using spherical samples rubbing against each other, to make a direct connection of the inter-particle tribology to the granular flow reported in our previous work [Phys. Rev. Lett. 126,128001 (2021)].
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