Research On Thermal-Mechanical Fatigue Strength Of Metro Vehicle Wheels And Parametric Design

With the further development of urbanization,the population in cities has increased dramatically,and the subway vehicle has played an important role in urban transportation due to its unique advantages.The safety and reliability of the wheel during service is the precondition of stable operation of subway vehicles.The wheels not only suffer from the whole loads between the wheels and the rails during service,but also the thermal load caused by the brake shoe braking.The subway wheels are subjected to more frequent braking thermal loads because the subway runs with sudden start and stop characteristics.In order to provide more reliable guidance to subway wheel maintenance,the fatigue strength of subway wheels under the combined thermal and mechanical loads is evaluated on the ANSYS platform.The premise of obtaining reliable simulation results is to draw accurate geometric models,and shapes of wheels are complex and diverse.Strict topological relationships between geometric elements are required.In order to improve the efficiency of drawing the geometric model of wheels,the parameterized drawing programs for different types of wheels have been developed on the Auto CAD platform.The fatigue strength of subway wheels under the combined effects of heat treatment residual stress,wheel-axle assembly stress,wheel-rail contact stress,and braking thermal stress are studied in this paper.The simulation analysis of the wheel heat treatment process is a transient nonlinear problem.In order to save computing resources,the indirect coupling method is applied and the two-dimensional axisymmetric model is established to simulate the residual heat stress of different types of wheels.The results show that the residual radial tensile stress is231.8 MPa in the wheel web.After fully analyzing the braking process of the wheels,the uniform heat flow method is applied and the two-dimensional axisymmetric model is established to simulate the changes in the wheel temperature field and stress field of different types of wheels during 30 continuous braking.The results show that the wheel maximum temperature increases with the number of cyclic braking,and the maximum temperature in the wheel web is up to 439.1℃,and the maximum radial stress is 333.3MPa.In order to study the wheel fatigue strength under the combined wheel-rail mechanical loads and other loads,the PLANE25 element is used to perform harmonic analysis to simulate the stress state of wheels under wheel and rail loads.Based on the standard AAR S-669,the Sines multiaxial fatigue strength evaluation criteria was used to explore the effects of different rim thicknesses,different web types,different station spacings and different initial braking speeds on fatigue strength.The results show that under the combine of multiple loads,(1)The wear-restrained wheels are more prone to fatigue failure.(2)The comprehensive fatigue resistance of S-shaped webs is better than that of straight webs and corrugated webs.(3)The smaller the distance between stations,the higher the maximum temperature and the maximum radial stress and the larger the increase.(4)The higher the initial braking speed,the higher the maximum temperature and the maximum radial stress,but the smaller the increase.