The effect of material properties on the thermoelastic stability of sliding systems

Frictionally excited thermoelastic instability (TEI) results in severe thermomechanical damage of clutches and brakes leading to localized surface burning of frictional materials, permanent distortions of metal plates, vibrations and noise. In this work, the analytical formulation proposed in [ASME J. Tribol. (2001)], rephrased in dimensionless form, is employed to estimate the influence of the material properties on the minimum critical speed of sliding systems. Two cases of practical interest are considered, an automotive multidisk clutch (dissimilar materials case) and a carbon-carbon brake/clutch for high speed applications (similar materials case). In both cases the relative importance in altering the minimum critical speed and the direction of change of each parameter is examined and a comparison with previous available solutions is performed. A simple and sufficiently accurate relation is found to hold between the sliding V or rotating Ω critical speed and the arbitrary material parameter ξ. Vmin = Ωmin = (ξ)n Vo Ω0 ξo which can be employed in estimating the optimum set of material properties for sliding systems. Typical sliding and rotating critical speeds are also given for automotive, railway and aeronautical applications, regarding both brakes and clutches.