Simulation And Analysis Of Temperature Field And Stress Field Of Train Brake Disc

The reliability of the brake disc is one of the main factors of influencing running safety. According to the application experiences of brake discs at home and abroad, cracks caused by thermal fatigue are one of the main reasons for the brake disc damage. So it is of significant importance to prevention of damages for thermal cracks, choice and design of material of brake discs that simulation of temperature field and stress field and analysis of influence of flaws of brake discs on thermal fatigue stress during braking process.In this paper, taking a certain train brake disc as the research object, the transient temperature field and stress field were studied during the braking process based on FEM software ANSYS. The influence of flaws on temperature field and stress field was discussed. The paper was focused as followed:1. The necessary loads and the boundary conditions in the finite analysis of the temperature field were discussed. A new method to calculate the heat flux generated by friction on friction surface of brake disc was proposed, which is based on friction power and hoop contact length distribution of contact couple. A method of converting heat radiation coefficient into convection coefficient was applied and therefore simplified the boundary conditions of thermal analysis.2. According to structural feature, the 3-D symmetric finite element model of the brake disc was established. The transient temperature field during the emergency braking process was simulated using two methods to calculate the heat flux on friction surface, which are friction power method and common energy conversion method. And the results were analyzed in detail and compared. The calculation results show that the friction power method can illustrate the effect of hoop contact length between disc and pad on temperature field distribution.3. The stress analysis of brake disc was done with sequentially thermal-structural coupling analysis during the emergency braking. The results show that the varied behavior of surface stress of the disc is from tensile stress to compressive stress and then returning to tensile stress under the action of thermal stress and centrifugal force. And the hoop stress is the main one to cause the crack initiation on the brake friction surface.4. The FEM models with internal shrinkage or surface crack were established. The temperature field and stress field analysis of models with imperfection was done. The results show that internal shrinkage can cause local high temperature and high stress upon the shrinkage. And the shrinkage can induce the crack initiation and propagation to surface. Surface crack has little influence to temperature field. Crack tip forms high tensile stress under the thermal load.5. The thermal-structural coupling FEM model of disc and pad was established. A method to simulate the relative sliding between disc and pad was proposed, in which pad rotation is controlled through loading bidirectional translational displacement. The thermal-structural coupling simulation was initially done. The results show that the thermal shock generated by rotational frictional heat causes fluctuation of temperature field and stress field. The temperature field and stress field are coupled during braking process. Ignoring the thermal-mechanical coupling efficiency will cause the thermal analysis error.