Thermal Load Analysis Of Brake Discs For 70% Low-Floor Tramcars

The low-floor tramcar is a means of transportation with high capacity of electrical drive and quiet smooth performance, which has the common advantages of buses and trains. Compared with the subway, the advantage is lower cost, well-adapted and its moderate passenger capacity.With the rapid development of the urbanization of China, the low-floor tramcar has been widely used. However the running condition of the vehicle is extremely adverse during the braking. The thermal loads on the brake discs caused by the frequent braking of the vehicle lead to the reduction of the fatigue life of the brake discs and endanger the safe operation of the vehicles. Therefore, it is very significant to build the simulation model of the three-dimensional finite element for the brake discs and research the distribution of both temperature field and stress field for predicting the fatigue life of the brake discs.In this paper,70% low-floor tramcars were taken as research objects. Based on the relevant theoretical knowledge, the related parts of the braking system were briefly introduced. And the braking calculation of two typical working conditions was accomplished including service braking and emergency braking. What’s more, the boundary conditions of the brake discs’thermal analysis were calculated for the motor car and the trailer of the low-floor tramcar.Firstly, in the paper the simulation models of the three-dimensional finite element were established for the brake discs of the motor car and trailer from 70% low-floor tramcars by using ANSYS software, considering that the thermal analysis research for the above is more comprehensive. And the three boundary conditions calculated are loaded into the model. Using the indirect coupling method, the transient-process simulation was analyzed to study the distribution and changing rules for the temperature field of the brake discs, especially for the brake discs of the trailer in service braking condition and both the motor car and the trailer in emergency braking condition. In addition, an innovative idea of the thermal analysis was researched for the brake discs under the rotating load in the software of ANSYS. The model of dynamical load function was proposed and deduced. By way of changing the angular velocity into the angle, the original expression of the heat flux loaded on the brake disc was also changed into the expression of heat flux under the rotating loads. Thus, the bottleneck problem with the calculation increased large was solved in the traditional method by converging results and reducing the time steps. Meanwhile, the simulated analysis of the temperature field was completed for the brake discs of the motor car and trailer under the rotating loads in the emergency condition. On the basis of the simulated analysis of the temperature field, the results were exerted on the nodes of the structure model of the brake discs as the temperature loads. Then the simulated analysis of the thermal stress field was accomplished for the brake discs in some operating conditions, and the distribution and changing rules of the thermal stress field were also researched. Finally, the number of the stress cycle was obtained in the paper for the brake discs of the motor car especially when the brake discs losing efficacy in the emergency conditions by using the Mason-Coffin formula and the prediction of the thermal fatigue life was also completed for the brake discs of 70% low-floor tramcars.