Weber B, Suhina T, Brouwer A M, Bonn D
Van der Waals-Zeeman Institute, Institute of Physics, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands.
Advanced Research Center for Nanolithography (ARCNL), Science Park 110, 1098 XG Amsterdam, Netherlands.
Sci Adv. 2019 Apr 5;5(4):eaav7603. doi: 10.1126/sciadv.aav7603. eCollection 2019 Apr.
When two objects are in contact, the force necessary to overcome friction is larger than the force necessary to keep sliding motion going. This difference between static and dynamic friction is usually attributed to the growth of the area of real contact between rough surfaces in time when the system is at rest. We directly measure the area of real contact and show that it actually increases during macroscopic slip, despite the fact that dynamic friction is smaller than static friction. This signals a decrease in the interfacial shear strength, the friction per unit contact area, which is due to a mechanical weakening of the asperities. This provides a novel explanation for stick-slip phenomena in, e.g., earthquakes.
当两个物体接触时，克服摩擦力所需的力大于维持滑动运动所需的力。静摩擦力和动摩擦力之间的这种差异通常归因于当系统静止时，粗糙表面之间实际接触面积随时间的增长。我们直接测量了实际接触面积，并表明尽管动摩擦力小于静摩擦力，但在宏观滑动过程中实际接触面积实际上是增加的。这表明界面剪切强度（即单位接触面积上的摩擦力）降低了，这是由于粗糙不平处的机械弱化所致。这为例如地震中的粘滑现象提供了一种全新的解释。
