Thermal Stress Simulation Analysis of Thermal Fatigue Crack on Brake Disc Surface
As the core component of the braking system of the railroad vehicle,the braking performance of the brake disk directly affects the operation safety of the vehicle.The large amount of braking thermal load will lead to hot spots on the surface of the brake disc,increasing the risk of forming radial cracks.The accurate evaluation of the performance of cracks is the key to predict brake disc life and guarantee the safety of the train,and it is necessary to study the influence of thermal-mechanical coupling of the brake disk.First,a three-dimensional finite element model of the axle-mounted brake disc of the subway train is established.Then,the finite element transient heat transfer model is used to calculate the heat flow input of two consecutive emergency braking using the friction power method.Finally,the temperature and stress field simulations of the cracks with different extension degrees are obtained by finite element simulation.The simulation results show that the temperatures at the centers of rectangular and elliptical cracks decrease by 30 ℃ and 43 ℃,respectively,compared with the control group.And the resulting temperature gradient caused the maximum equivalent stresses to increase by 60.3％and 88.9％,respectively(up to 505 MPa and 595 MPa,respectively).The influence of individual cracks with different extension patterns on the temperature and stress fields are significantly different,while multiple cracks will lead to the increase of equivalent stress on the nearby disk surface.The increase of radial cracks on the brake disk surface will further increase the stress peak,which is more likely to lead to the material fatigue damage and crack extension,affecting the safe operation of the train.
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