Thermoelastic instability in a thin layer sliding between two half-planes: transient behaviour

The susceptibility of brakes and clutches to the known phenomenon of frictionally-excited thermoelastic instability is estimated studying the interface temperature and pressure evolution with time. A simple model has been considered where a layer with half-thickness a slides with speed V between two rigid and non-conducting half-planes. The advantage of this fairly simple model is that it permits us to deduce analytically the critical conditions for the onset of instability, that is the relation between the critical speed Vcr and the growth rate b of the interface temperature and pressure. It has then been verified that as the thickness a reduces the system becomes more and more prone to instability, and that a symmetrical pressure/temperature distribution at the layer interfaces can be more unstable than an antisymmetrical one. Moreover, the analysis of the evolution of the system beyond the critical conditions has shown that even if low frequency perturbations are associated with small critical speed, they might be less critical than high frequency perturbations if the working sliding speed is much larger than the actual critical speed of the system.