Instability scenarios between elastic media under frictional contact

• Instability scenarios occurring in mechanical systems with frictional contact.
• Switch between stick–slip and modal instability in function of system parameters.
• The presented results allow for generalizing mode coupling instabilities.
• Structural damping affects the macroscopic frictional behaviour.

This article presents the results of a numerical dynamic analysis of two bodies in sliding contact. The 2D model consists of two finite elastic media separated by a contact interface, governed by classical Coulomb friction law. The aim of this work is to investigate the instability scenarios occurring when friction forces excite the mechanical systems during the relative motion; simulation results show that the coupling between the frictional behaviour at the contact and the global dynamic of the system can bring to either stick–slip phenomena, or mode coupling instability. Complex eigenvalue analysis and transient non-linear simulations highlight how system parameters, like structural damping, affect the macroscopic frictional behaviour, switching from stick–slip phenomena to harmonic vibrations (due to mode coupling instability), up to the stable sliding state. The presented results allow for generalizing the instabilities due to mode coupling, named in brake squeal literature “lock-in” instability, to any mechanical system with frictional contact. The analyses show how maps of the instability scenarios can be drawn as a function of different parameters to help the design of systems in frictional contact.