DYNAMICS OF RUPTURE AT FRICTIONAL ROUGH INTERFACES DURING SLIDING INITIATION

The aim of this work is to present the results from a non linear finite element analysis in large transformations of the contact interface between two deformable bodies when sliding initiates and the roughness is introduced at the contact surfaces. The two-dimensional in-plane dynamic model consists of two different isotropic elastic media separated by an interface governed by Coulomb friction law, and subject to remotely applied normal and shear tractions (pre-stress phase). Once the ratio between the local values of tangential and normal stresses reaches the limit value, the sliding initiates and local ruptures are activated (nucleation phase). The propagation of the ruptures over the interface and the wave propagation inside the solids are analyzed. The interactions between the waves propagating into the two solids (P waves, shear waves, surface waves) give raise to different types of ruptures. They can be classified depending on their velocity front (sub-Rayleigh, sub-shear, super-shear) or on their interface states (pulse-like, crack-like). A sinusoidal roughness is introduced at the contact surfaces and the analysis is performed for different values of the roughness parameters. Depending on the relative dimension between the roughness wavelength and the width of the wave fronts, two different behaviour can be observed: i) a coupling between the wave propagating into the two bodies; ii) a decoupling of the wave propagation inside the two materials, characterized by an independent wave propagation. First the wave propagation is analyzed when a single rupture is originated in pre-sliding conditions; successively, the wave generation during sliding initiation is addressed.