Investigation of the Thermal Vehicle Brake Behavior During the Vehicle's Development Phase by Co-Simulation 2007-01-3935

The mathematical thermal design of the vehicle brakes will lead to success if all influence parameters such as friction (fading effect), car geometry and inertia, brake amplifier, tire, convective heat flow, heat conductance and heat radiation are taken into consideration. In addition to a lot of design criteria, the thermal stability of the vehicle brake is becoming more and more important because of permanently increasing engine powers and weight of the vehicles. This requires both stable friction behavior in the contact zone between brake lining and brake disk and a sufficient transfer of the friction energy by means of convective heat flow. In order to accomplish these two tasks, considerable expense on a brake test bed and innumerable brake trials are necessary. It must be guarantied at the end of the brake design process that the vehicle reaches the required braking distance and the thermal stability of the brake, e.g. after several freeway braking sequences. In spite of all extensions, there is no closed simulation model known applicable for practice until today, that both fading effect and self-induced vibrations (NVH) of the brake can be modeled satisfactorily as a part of the vehicle.

A combined procedure for simulating of the performance of automotive disk brakes is presented in the present work. The introduced software interface between MATLAB and ANSYS can guarantee the automatic co-simulation. This includes not only the non-steady state temperature distribution and the fading behavior due to several vehicle brakes simultaneously, but also several braking procedures sequentially. Additionally, the theoretical background and the practical appliance of a 3D FEM-simulation of the non-steady state brake thermal behavior in MATLAB is introduced. A new approach for measuring of the friction is also presented. This approach can be used as an input for a dynamic brake vehicle co-simulation.

An intelligent concept for modeling of the cool down behavior due to the convective heat flow around the vehicle brake is proposed by means of CFD-simulation using FLUENT. This should allow fulfilling the requirements of realistic simulated results of the brake cool down behavior by consideration of all vehicle components influencing the convective heat flow through the vehicle chassis.