Transient frictionally excited thermoelastic instability analysis of two dimensional axisymmetric friction brake

A mathematical model on thermoelastic instability (TEI) of two dimensional axisymmetric friction brake is proposed by considering the impact of friction layer's thickness. Based on the perturbation method, temperature perturbation of the brake pair and the characteristic balance equation under different types of distribution of hot spots are respectively derived. The change rules of the critical speed and growth rate of perturbation are studied. Transient normal temperature of the frictional surface changing with time is calculated. The effects of brake pair's different thickness ratio, thermal conductivity, elastic modulus, specific heat and thermal expansion coefficient on critical speed are analyzed and compared. The results show that the critical speed of the model whose hot spots are antisymmetrically distributed is much lower than that of symmetric mode and it will decrease firstly and then grow again with the increase of wave number. The growth rates of perturbation of different wave numbers have a approximate linear relationship with the sliding velocity. Meanwhile, the perturbation which has the lowest critical speed has the largest growth rate. For perturbations with wave number smaller than critical value, the temperature will increase, vice versa perturbations with wave number greater than critical value, the temperature will decrease. The stability of the braking system can be enhanced by increasing the thickness of the brake pair, thermal conductivity, specific heat of the friction layer and decreasing the thermal conductivity, thermal expansion coefficient of the sliding layer and the elastic modulus of the friction layer. © 2015 Journal of Mechanical Engineering.