Research On Tread Braking Heat Load Of Wheels Based On Fem

With the development of the heavy-haul transportation, the safety of the rolling stock is increasingly outstanding. The brake capability is very important to ensure the safety of train, especially when train is operated under the condition of long ramp cycle braking in Datong-Qinhuangdao heavy-haul line. For the freight train, tread braking is still the main braking type. So the heavy-haul wheels are working under the condition of more strong friction, high heat load and large wheel-rail interaction force. Above all, thermal fatigue damage is one of the main failure types for heavy-haul wheel.In this paper, the features of heavy-haul technology at home and abroad were reviewed. Firstly the status and development of thermal damage research of wheels were introduced. Then thermal damage forms and theory were studied. Subsequently the condition of Datong-Qinhuangdao heavy haul line was described and based on its all line ramp settings the heat load was obtained. The solution methods for temperature field and stress field, the coupled field analysis method and the elastic-plastic theory were studied. Finally the boundary condition for temperature field and stress field solutions were defined and load cases for strength analysis of wheel were also confined.Based on thermal theoretical research, the boundary condition of the heat analysis for wheel was calculated. When the traction load of trains is 10000t and the braking speed limit is 80km/h, the temperature field and stress field of the 23t and 25t axle load wheels were simulated in Datong-Qinhuangdao heavy-haul line. Then the static and fatigue strength of the wheels were assessed. According to the analysis results of 25t axle load wheel, in order to satisfy the strength requirement of wheel, heat damage must be decreased by increasing the thickness of wheel rim. With the same conditions, the temperature field and stress field of the 30t axle load wheels and its strength behavior were also researched.The following results can be obtained: (1) During the cycle braking, the temperature of the tread changes alternatively and the maximal temperature occurs at the braking clock 243.75min. The temperature of the tread is high in the middle position and low in both sides. (2) The change trend of the heat stress is the same as the temperature. The maximal heat stress also appears at the braking clock 243.75min. (3) The static strength requirement of all kinds of axle load wheels is satisfied. The fatigue strength requirement of new 23t and 25t axle load wheel is satisfied, but the fatigue strength requirement of the wear 25t axle load wheel with the diameter of 786mm is not satisfied. For 25t axle load wheel, when the diameter of wheel is 810mm, the fatigue strength requirement just is satisfied. (4) The static and fatigue strength requirement of 30t axle load wheel are satisfied. For the new wheel, the strength allowance is relative large, but the strength behavior of the wear wheel is very close to the permitted value. The maximal wear loss of wheel rim of 25t axle load wheel is 30mm, while the maximal wear loss of 30t axle load wheel is 45mm.