Wheel-Rail Interaction Due To Rail Weld Irregularity And Its Safety Threshold In Heavy Haul Railway

Heavy haul railway is an effective measure for improving railway transportation capacity and efficiency. It’s imperative to accelerate the development of heavy haul transportation in Chinese Railway. With the increase of axle load and speed, the dynamic characteristics of wheel-rail system present some further deterioration. Especially when the freight wagon with large axle load passing through the rail welding section, it will aggravate the wheel-rail interaction, deteriorate the track conditions, and even cause the line irregularity and rail damage. So, the influence of the rail weld irregularity on wheel-rail interaction is analyzed in this paper, and the safety threshold of the weld irregularity is put forward, so as to play a crucial role in reducing the rail welding joint maintenance and prolonging service life.The weld irregularities are measured on heavy haul railway in China, which are utilized as the input excitation of wheel-rail interface. Under the excitation of welding joint, dynamic performance of heavy load freight car with different axle load is studied based on the theory of vehicle-track coupled dynamics. Results indicate that the wheel-rail dynamic behavior has significant change under the concave type of weld irregularity. Conversely, the wheel-rail dynamic interaction excited by the convex type of welding irregularity is not so severe, and also the evaluation indices meet the standard requirements.Under the theoretical concave weld irregularities, the wheel-rail dynamic interactions of different axle load freight wagons are analyzed, and the comparison with the measured irregularities is carried out. The results show that, while the short wave length increases, the reduction ratios of wheel-rail force and wheelset acceleration with the axle load of25t are bigger than those with the axle load of27t and30t. With the growth of short wave depth, the increase amplitude of wheel load reduction rate with the axle load of25t is larger than that with the axle load of27t and30t. It is found that the existing theoretical model of concave welding irregularity can’t reflect the fact very well. So, the theoretical model is modified. There is no difference in the wheel-rail dynamics indices between modified irregularity and field test weld irregularity.For the convex weld irregularity, a theoretical model is proposed. The wheel-rail dynamic interactions of different axle load freight cars excited by the theoretical irregularity are simulated and compared with those in the case of the measured irregularity. Results indicate that the wheel-rail force increases sharply and the vibrations of wheelset and rail have little change with the increase of axle load. Wheel-rail dynamic indices increase with the growth of wave depth. These indices decrease extremely with the increase of the wave length. The results of wheel-rail dynamics indices excited by the theoretical and field test weld irregularities agree very well.Further more, the impacts of wave length and depth on the dynamic response of different axle load freight car are studied. The related safety threshold values are obtained. Results show that it is strict to prevent the irregularity with the wave length of0.2m or less. The wheel-rail dynamic indices for different axle load freight wagons can meet the demands when the concave-convex vector displacement of short wave irregularity in the rail welding section is no more than0.5mm.