A full simulation of the process is possible but is prohibitively computer-intensive because of the small time step required for discretization of the heat conduction equation. Instead, a perturbation method is used to determine the stability boundary and the resulting equations are discretized leading to an eigenvalue problem for the critical speed. Current work is focussed on developing this method to the stage at which it can be transferred as a finite element package to industry. There are also several unanswered problems concerned with the fact that a given point in the disk makes only intermittent contact with the pad. Experimental Investigation of Automotive Disk Brakes Arising out of the above project, a parallel experimental investigation is projected to use embedded thermocouples to track the development of unstable temperature perturbations under various operating conditions.
Preliminary results show several different temperature patterns can develop.
The resistance is generally pressure-dependent and the contact pressure depends on the thermoelastic distortion of the partially solidified casting. Thus, the heat transfer, solidification, thermoelastic, and contact problems are coupled through the boundary conditions. Earlier simulations show that the coupling is potentially unstable and that nominally uniform processes may be perturbed by the growth of a perturbation in temperature field and solidification front. Current work is focussed on the use of realistic constitutive laws for the material, including temperature-dependent properties and viscoelastic effects. Appropriate Models for Coulomb Friction Contact problems involving friction are known to exhibit non-uniqueness of solution if the friction coefficient is sufficiently high.