Heat Load Analysis Of Heavy-Haul Freight Car Wheel For Tread Breaking

In order to improve the transport capability of the freight car, the 25t axle load of the vehicle have been developing, the axle load of general freight car has been planning increased to 27t and the purpose freight car increased to 32.5t on the premise of the speed is raised to 120km/h. As the tread braking is the main braking of the freight car, the heat load problem of the railway wheel stands out along with the increase of the axle load. The effect of the heat load of the 32.5t axle load on the wheel under the typical braking has been studied in the paper.The temperature filed boundaries of two different breaking conditions were calculated respectively, the long falling ramp breaking with the velocity of 80km/h and the emergency brake with the 100km/h initial velocity and 1400m emergency braking distance. And then the indirect coupling of simulating the temperature field and stress field of in the both breaking conditions was adopted, and the static strength and fatigue strength of the wheel spoke were evaluated.The primary work and conclusions of the paper are as follows:In order to determine the temperature field conditions, the heat flux input into the wheel was calculated by adopting the energy transform process, also the heat convection and radiation were considered.Calculation results of the temperature filed show that the maximum temperature of the wheel tread under the long falling ramp breaking condition appears when the breaking is at the end. The maximum temperature of the new wheel tread appears when the breaking time is 32s and the maximum temperature of the wear wheel tread appears when the breaking time is 35s under the emergency brake condition. The maximum temperature always appears on the tread friction with brake under the both breaking conditions, but the maximum temperature on the wheel tread under the emergency brake condition is bigger than the other breaking condition.Calculation results of the heat stress filed show the maximum von-Mises stress under the long falling ramp breaking condition appears on the spoke when the breaking is at the end. The maximum von-Mises stress under the emergency brake condition appears on the new wheel spoke when the breaking time is 27s, which appears on the wear wheel spoke when the breaking time is 57s. The maximum von-Mises stress appears on the wheel spoke under the first breaking condition is bigger.Only under the mechanical load, the static strength of the wheel spoke meets the requirement. The fatigue strength of the spoke has been analyzed applying the Goodman curve in which determined the stress distribution under the wheel spinning a week and got the stress amplitude and average stress. That we say the fatigue strength of the spoke under the mechanical load satisfies the requirement.Under the joint action of the heat and mechanical loads, the static strength and fatigue strength of the new wheel spoke meet the requirement. The static strength of the wear wheel spoke meets the requirement while its fatigue strength under the emergency brake condition doesn't meet the requirement.