Simulation Analysis Of The Wheel Tread Braking Thermal Load

With the increasing number of high-speed rail lines and continuous urban metro construction, both the high-speed of rail vehicle and the requirement for frequent braking for a long time in a short distance need a high ability of braking for rail vehicles. For most rail vehicles with air brakes, the kinetic energy of the vehicle will finally be transformed into the thermal energy by the friction between the shoe and the wheel tread or brake disc. It’s necessary to have a thermal simulation of wheel tread braking.By building a three-dimensional transient conducting mathematic model and wheel’s surrounding air hydrodynamic model, in the thesis firstly studied is the relation to the convective heat transfer coefficient among the initial temperature and the wheel shape. Then some reference comments are given on design of wheel shape by a thermal load analysis. At last the fatigue damage behavior of the wheel spoke is analyzed in the process of the wheel abrasion under the combination of braking and thermal load.In the braking processing, the convective heat transfer coefficient of the air around the wheel varies all the time which makes it difficult to set the exact coefficient in thermal simulation. Therefore, chapter three calculates the convective heat transfer coefficient of the air around the wheel for an emergency braking by building a wheel’s surrounding air hydrodynamic model. Then the relation to the convective heat transfer coefficient among the initial temperature and the wheel shape are obtained by changing these two parameters.By the model built in chapter three, the wheel shape is optimized by setting proper coefficient of convective heat transfer in the thermal simulation in chapter four. It shows that it’s better to choose the width of the shoe in the range of 80-86 mm and the thicker the wheel rim is, the lower the temperature and the stress will be after braking. The width of the wheel rim has little influence on the braking heat. The S-shape spoke has better stress state after braking.In chapter five the fatigue damage behavior of the wheel spoke in the process of wheel abrasion is analyzed. Under the mechanical load, the stress state become poor when the wheel spoke rounded corners’abrasion increases. And the braking load makes the fatigue damage of the wheel spoke worse.