标题： 静态摩擦系数随界面从单峰接触到多峰接触的增长而减小 显示英文标题

标题： The Decrease of Static Friction Coefficient with Interface Growth from Single to Multiasperity Contact

摘要： 描述滑动开始时摩擦强度的关键参数是静摩擦系数。 然而，如何从微观尺度接触的峰谷在宏观尺度上产生静摩擦系数仍然是一个开放问题。 在这里，我们进行了摩擦实验，其中正压力变化超过三个数量级，从而实现了从低负载下的单峰谷接触到高负载下的多峰谷接触的转变。 我们发现随着正压力的增加，摩擦下降（静摩擦力与动摩擦力的比值）显著减少。 使用一个简单的粘滑过渡模型，我们确定滑动前和亚临界接触点的存在是正压力增加时静摩擦系数较小的原因。 我们的测量和模型弥合了在微观力下通常在原子力显微镜实验中观察到的摩擦行为，以及在宏观力下工业相关的多峰谷接触界面之间的差距。 显示英文摘要

摘要： The key parameter for describing frictional strength at the onset of sliding is the static friction coefficient. Yet, how the static friction coefficient emerges at the macroscale from contacting asperities at the microscale is still an open problem. Here, we present friction experiments in which the normal load was varied over more than 3 orders of magnitude, so that a transition from a single asperity contact at low loads to multiasperity contacts at high loads was achieved. We find a remarkable reduction in the friction drop (the ratio of the static friction force to the dynamic friction force) with increasing normal load. Using a simple stick-slip transition model we identify the presence of presliding and subcritical contact points as the cause of smaller static friction coefficient at increased normal loads. Our measurements and model bridge the gap between friction behavior commonly observed in atomic force microscopy experiments at microscopic forces, and industrially relevant multiasperity contact interfaces loaded with macroscopic forces.