Role of damping on contact instability scenarios

In the last years, many studies have been dedicated to investigate sliding contact issues between deformable bodies. Local frictional behavior and its interaction with the global dynamics of the system has been the subject of many works in several disciplines as tribology, geophysics, vibration mechanics and fracture mechanics. Experimental and numerical papers have focused the attention on the understanding how local interface dynamics (wave and rupture propagation) affects the macroscopic frictional behavior of the system during instability regime (stick-slip instability, mode coupling instability) and conversely. The stick-slip regime is characterized by sudden friction force drops (sliding state) along the time, separated by period of elastic energy accumulation (stick state). Instead, the modal dynamic instability occurs when a vibration mode of the mechanical system becomes unstable, due to frictional contact forces. This kind of instabilities, generated by frictional forces, has been mainly object of papers [5] dealing with a specific issue named brake squeal. However general and common mechanical system can generate harmonic acoustic emission comparable to brake squeal noise during relative motion with frictional contact. In such context, the role of material damping on the frictional dynamics has been investigated by a simple frictional elastic model. Comparison between nonlinear transient simulations and complex eigenvalues analysis allowed for investigating different instability scenarios for general systems in frictional contact and drawing a qualitative map in function of damping parameters. Moreover, the results show the importance on defining a good estimation of damping to modeling system with frictional contact, in order to have reliable results. Finally a brief comparison between numerical and experimental results has been carried out.