Stress Waves Propagation Along the Frictional Interface with a Micro-contact

The stress wave profile at the frictional interface is crucial for investigating the frictional process. This study modeled a brittle material interface with a micro- contact to analyze the fine stress wave structure associated with frictional slip. Employing the finite element simulation alongside the related wave theory and experiments, two new wave structures were indentified: A Mach cone symmetric to the frictional interface associated with incident plane wave propagation, and a new plane longitudinal wave generated across the entire frictional interface at the moment when the incident wave began to propagate. The time and space of its appearance implies that the overall response of the frictional interface precedes the local wave response of the medium. Consequently, a model involving characteristic line theory and the idea of Green's function has been proposed for its occurrence. The analysis results show that these two new wave phenomena are independent of the fracture of micro-contacts at the interface; instead, the frictional interface effect may be responsible for the generation of such new wave structures. The measured wave profiles provide a proof for the existence of the new wave structures. These results display new wave phenomena, and suggest a wave profile for investigating the dynamic mechanical properties of the frictional interface.