Effects of Stress Distribution at the Contact Interface on Static Friction Force: Numerical Simulation and Model Experiment

This study develops a simplified model that can simulate the dynamics of a split contact interface at the transition from static to kinetic friction. The model has a contact interface formed by multiple contacting points connected to a rigid base via a spring. From a numerical analysis of this model, the effect of the stress distribution at the contact interface on the level of static friction force was investigated. Consequently, it was found that the existence of the stop-restart motion can act to increase the macroscopic (apparent) static friction force. Thus, the numerical analysis demonstrated that the macroscopic static friction coefficient could be changed without varying the local static friction coefficient. The type of tangential loading history, i.e., the existence of stop-restart motion, is an important factor for characterizing the level of the static friction force. In other words, this implies that we can adjust the level of the macroscopic static friction coefficient without changes to the local static friction. Furthermore, the above numerical prediction was confirmed by a model experiment focusing on the sliding contact interface of an object built from separated rubber blocks.