Wheel wear is one of the most critical factors affecting the vehicle performances and maintenance costs of railway vehicles. However, previous research has to ignore the initial wheel-rail profiles for the evolution of wheel wear. Therefore, this work investigates the relationship between the evolution of wheel wear corresponding to different initial wheel-rail profiles and vehicle dynamics, wheel-rail deterioration. Firstly, the evolution of wheel wear during a long service period is measured from two high-speed railway trains running on two different lines. Contact geometry, e.g., equivalent conicity and contact pair distribution, are extracted. After that, the influence of wheel wear on the vehicle dynamic performance is studied using a multi-body dynamic software. The calculated contact parameters, e.g., pressure, shear traction, and creepage, are used to analyze the distribution of rolling contact fatigue. Based on the experimental and simulation results, the initial wheel and rail profiles significantly affects the wheel wear pattern, the thin rim wheel has uniform wear, and other wheels occurs hollow wear. The hollow wear can lead to gradual deterioration of vehicle dynamics, which conversely aggravates the wheel reprofiling.

Small changes to wheel-rail profiles can have a significant impact on the equivalent conicity and vehicle dynamics. Previous research has focused mostly on worn wheels, however, with little attention to different types of rail profile deviation and their influences on vehicle dynamics. Therefore, the specific objective of this paper is to investigate the individual and combined influences of various rail profiles and multi-parameter couplings on the hunting instability of railway vehicles. This paper first obtains the distribution law of rail profile deviation from a statistical analysis of several rail profiles with long-term measurements. Then, the equivalent conicity of rail profiles that match the studied wheel profiles, gauges and wheelback distances is compared. The dynamic model for the vehicle has been established. Finally, the measured rail profiles and wheel profiles, as well as the combinations of the gauges, wheelback distances, friction coefficients and key suspension characteristics are integrated into the simulation model to analyze the atypical phenomenon of the carbody hunting and the bogie hunting. According to the findings, rail profile deviation has a significant impact on equivalent conicity and the evaluation of vehicle stability when subjected to multi-parameter coupling, particularly for worn wheels. Therefore, strict limits of rail profile deviation have to be considered in track maintenance for vehicles running at speeds of 300 km/h or higher.

Purpose: This study aims to reduce the redundant weight of the anti-roll torsion bar brought by the traditional empirical design and improving its strength and stiffness.Design/methodology/approach: Based on the finite element approach coupled with the improved beluga whale optimization (IBWO) algorithm, a collaborative optimization method is suggested to optimize the design of the anti-roll torsion bar structure and weight. The dimensions and material properties of the torsion bar were defined as random variables, and the torsion bar's mass and strength were investigated using finite elements. Then, chaotic mapping and differential evolution (DE) operators are introduced to improve the beluga whale optimization (BWO) algorithm and run case studies.Findings: The findings demonstrate that the IBWO has superior solution set distribution uniformity, convergence speed, solution correctness and stability than the BWO. The IBWO algorithm is used to optimize the anti-roll torsion bar design. The error between the optimization and finite element simulation results was less than 1%. The weight of the optimized anti-roll torsion bar was lessened by 4%, the maximum stress was reduced by 35% and the stiffness was increased by 1.9%.Originality/value: The study provides a methodological reference for the simulation optimization process of the lateral anti-roll torsion bar.

With the continuous increase in high-speed train operation speeds, lightweight bogie design has become a key means to enhance dynamic performance, which also increases the risk of structural fatigue. High-frequency wheel–rail excitations are transmitted to the bogie frame and couple with its higher-order modes at around 200 Hz, inducing local high-frequency resonance. This coupling markedly increases the stress amplitude within the affected frequency range and accelerates vibration-induced fatigue damage. This study investigates the vibration fatigue characteristics of a bogie frame with an inner axle box under high-speed operation and wheel polygon wear conditions. Using a high-speed wheel–rail interaction test rig, dynamic stresses and the vibration acceleration of the bogie frame are measured under different speeds and polygon orders. Based on modal analysis and vibration fatigue methods, a high-frequency vibration fatigue assessment method for the bogie is developed. Wheel polygon significantly amplifies mid-to-high-frequency vibration energy, and for the bogie frame with an inner axle box, pronounced modal coupling is observed at around 200 Hz. In particular, under the 11th-order polygon condition, the equivalent stress at critical locations such as the traction motor seat weld seam exceeds the fatigue limit, while the effect of the 20th-order polygon is relatively mitigated. The proposed vibration fatigue assessment method provides a theoretical basis for the safe design and operational maintenance of high-speed trains with bogie frames with inner axle boxes.

Purpose: In order to systematically grasp the changes and matching characteristics of wheel and rail profiles of high speed railway (HSR) in China, 172 rail profile measurement points and 384 wheels of 6 high-speed electric motive unites (EMUs) were selected on 6 typical HSR lines, including Beijing–Shanghai, Wuhan–Guangzhou, Harbin–Dalian, Lanzhou–Xinjiang, Guiyang–Guangzhou and Dandong–Dalian for a two-year field test.Design/methodology/approach: Based on the measured data, the characteristics of rail and wheel wear were analyzed by mathematical statistics method. The equivalent conicity of wheel and rail matching in a wheel reprofiling cycle was analyzed by using the measured rail profile.Findings: Results showed that when the curve radius of HSR was larger than 2,495 m, the wear rate of straight line and curve rail was almost the same. For the line with annual traffic gross weight less than 11 Mt, the vertical wear of rail was less than 0.01 mm. The wear rate of the rail with the curve radius less than 800 m increased obviously. The wheel tread wear of EMUs on Harbin–Dalian line, Lanzhou–Xinjiang line and Dandong–Dalian line was relatively large, and the average wear rate of tread was about 0.05–0.06 mm·(10,000 km)⁻¹, while that of Beijing–Shanghai line, Wuhan–Guangzhou line and Guiyang–Guangzhou line was about 0.03–0.035 mm·(10,000 km)⁻¹. When the wear range was small, the equivalent conicity increased with the increase of wheel tread wear. When the wear range of wheel was wide, the wheel–rail contact points were evenly distributed, and the equivalent conicity did not increase obviously.Originality/value: This research proposes the distribution range of the equivalent conicity in one reprofiling cycle of various EMU trains, which provides guidance for the condition-based wheel reprofiling.