Research On Wheel/Rail Wear Of Heavy Haul Freightcar On Vehicle System Multibody Dynamics

Since 2006, the 25t axle load railroad freightcars began to run on Da-Qin railway line.At the year of 2014, the next generation of 27t axle load freightcars were put into business operation on Da-Qin railway, while 30t axle load freightcars began operation trial on Shuo-Huang railway.All of the achievements open the heavy haul era of china. With axle load increasing, the wheel/rail wear and dynamical problems become much more prominently. More than 95% wheels of 25t axle load coal gondola on Da-Qin railway need to reprofile within 2 years. Wheel/rail wear problem restricte the heavy haul development significantly, and even endanger the operation safe, which is one of the core technical issues of the heavy haul.Based on the wheel/rail wear investigation and field test of existing railroad freightcars, the heavy axle load wagon wheel/rail wear simulation models are established.In this thesis ,a series of wheel/rail wear issues under the Chinese railroad heavy haul service condition have been researched,such as the effect of wheel/rail interface management on wear, typical wheel wear formation and maintenance limit, the coupling relationship between wear and vehicle dynamics performance ,the effect of track friendly bogie reducing the wear ,and the wear during the vechile braking.The main research works of this thesis are as follows:1 .The dynamic model with actual structure, parameters and running condition of China heavy haul railroad freightcars were established. Stick-slip dry friction model for major components like wedges, etc, and rigid flexible coupling dynamic model for main componets with large deformation such as steering arm of radial bogie. The results show that:The wedge model based on dry friction contact model simulation results, particularly the relative friction coefficient is very close to test. What is more, the dry friction contact wedge model can reflect the influence of vertical loaded frequency, etc on the damping capacity,and provide lateral friction and hysteresis loop characteristics of the bogie warp stiffness. For radial bogies, steering arm structural stiffness has influence on the vehicle dynamic performance obviously. So the rigid flexible coupling dynamic model is applied to improve the calculation precision, lightening design and dynamic performance.2.In this thesis, all of the vehicle dynamics model, wheel/rail contact model,wheel/rail wear model, wheel/rail profile update and operation condition are organized into the SIMPACK dynamic software with "user routines" .So wheel/rail wear can automatic iterative calculate online.Based on wheel/rail creepage theory,different contact model,such as FASTIM and CONTACT with efficiency and precision ,has been applied into different wear calculation stages. At the wheel/rail profiles rebuild process, Using Chebyshev Polynomial curve fitting method to improve the smoothness of original data,and decrease unreal multipoint contact caused by localized rag, which leads to the improvement of the robustness of wear calculation.3. Frist of all,the model above is used to study the wheel/rail interface management technology including the profile, material and friction control method of China heavy axle load railroad freightcars. The results show that: when the standard wheel LM profile matched the R75 rail profile,the wheel/rail contact spot area and stress change greatly, and the wheel/rail wear is significantly larger than that of R60 rail, so R60 rail with improved strength is more suitable for the actual situation of heavy haul railway in China. After the using of new material CL70 steel wheels with higher hardness, the value of rail wear increasing is much smaller than the wheel wear reducing. Under the simulation condition,the rail wear area only increased by about 2.48% maximum, while the wheel wear area can be reduced by about 31.87%, which means a high economic value.The appropriate wheel/rail interface friction control also can reduce the wear significantly. On the curve line, the rail side friction control only reduces wheel flange wear and rail side wear of high rail. The rail side+ rail top friction control reduces the wheel/rail wear on both two rails at the same time,whether straight or curve railroad.4.The investigation shows that the hollow and flat wear which formed by partial abrasion on the wheel are the typical wheel wear modes of heavy haul railroad freightcars in China. The origin,development of those typical wheel wear,and whose effects on vehicle dynamic performance and wheel/rail interaction have been studied. It showed that the maintenance limit of the hollow wear depth should be recommended as 2.0mm, and wheel flat depth should be recommended as 1.0mm.5. The relationship between wheel wear and vehicle dynamic performance is coupled.According to the simulation results, the wheel wear is approximately linear with vehicle running mileage, axle load and running speed. Therefor, the recommend economic operation speed of different axle load wagons can be determined based on the 'equivalent wear amount of the wheel'. In addition,the research shows that radial bogie is an effective technical means to realize characters of low power, low running resistance, low energy consumption and low wear of heavy haul railroad freightcars.6. Assuming the brake shoe wear is linear with the brakeshoe/wheel friction power ,the wheel/rail wear model is generalized to build the brakeshoe/wheel wear model. In the braking model,the air brake system characters on carbody and brake structure on bogie are took into concideration. The simulation results show that:the wear rate of brake shoes in Da-Qin railway under braking condition is calculated as about 3.63mm/ 10,000 km, and the average wear depth and wear area of wheel will increase by about 6.21% and 3.73%respectively after taking brake into consideration .