Study on thermoelastic instability of disk brakes in frictional contact

Abstract

Frictionally excited thermoelastic instabilities and transient thermoelastic behaviors have been investigated for the disk brake system subject to thermal and mechanical loads under the braking process. Both thermoelastic stability and time domain analyses have been performed to comprehensively understand the thermoelastic phenomena. First, the present study has focused on the theoretical analysis of the onset of thermoelastic instability using the linear perturbed method. Through the thermoelastic stability analysis, it is found that the onset of thermoelastic instability of disk brakes is characterized by antisymmetric mode. Also, it is observed that the thermoelastic stability boundary for the axisymmetric model exists between the two-dimensional solutions except for the small wave numbers. Secondly, the transient thermoelastic contact behaviors of disk brakes have been numerically simulated by a finite element method based on the coupled theory in which temperatures and deformations are mutually affected. Through the transient analysis, the thermoelastic instability phenomena (the unstable growth of contact pressure and temperature) have been investigated during the braking process. The effects of material properties on the thermoelastic behaviors have been examined for the disk brake, and the largest influential properties are found to be the thermal expansion coefficient for the disk and the elastic modulus for the pad. In addition, the thermoelastic analysis has been performed for the carbon-carbon composite disk brakes. Due to the excellent thermo-mechanical material properties, carbon-carbon composites not only can be less prone to thermoelastic instability than materials commonly used in automotive applications but they also reduce the thermo-mechanical damage of brake system. Finally, experimental studies have been performed for the disk brake system using a dynamometer. The dynamometer testing showed thermal deformations and vibration phenomena of t...