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Abstract A wealth of practical cases indicates that the fatigue failure of subway bogies primarily stems from the modal resonance of the structure. If the modal characteristics of the entire vehicle, including equipment and bogies, are mismatched, rail vehicles may experience abnormal vibrations and noise. Therefore, it is imperative to conduct modal analysis and matching design for subway vehicle bogies to ensure smooth operation, reduce structural vibrations and noise, and enhance vehicle safety and ride comfort. Modal identification methods under the ambient l excitations during vehicle operation were employed to identify the modal parameters of the bogie structure before and after wheel reprofiling and under different load conditions. According to the test results, wheel reprofiling has minimal impact on the modal parameters of the structure, but with an increase in load, the modal frequencies of each order generally increase. This is associated with boundary constraint states, such as the increased stiffness of the bogie air spring with an increase in vehicle load. By comparing the test results with simulation analysis results of the bogie structure under free and constrained states, it is evident that simulating realistic boundary constraint conditions is crucial to ensure the accuracy of the finite element model. Based on frequency isolation criteria and vibration isolation theory, a frequency planning basis for the bogie structure was established. The study found that as the vehicle load increases, changes in the boundary conditions of the bogie affecting the elastic modal frequencies of the structure may have a certain impact on matching design, and may even better comply with the requirements of frequency management equations. This provides a new direction for subsequent scholars researching modal matching design.

Rack rail vehicles show strong capability of mountain climbing and have become a popular transportation mode for mountain areas in recent years. Therefore, this paper investigated on the dynamic performance of rack rail vehicle through simulation of a multibody dynamic model. Firstly, a multibody dynamic model of rack rail vehicle considering both the wheel/rail interaction and the gear-rack meshing was developed in the SIMPACK software platform. A rack rail with a large slope of 250‰ was taken into consideration in the proposed study. Subsequently, the gear-rack meshing dynamics in terms of the meshing stiffness and the meshing force in both circumferential- and radial- directions were investigated. Moreover, two types of driving modes were compared to illustrate the effects of driving mode on the wheel/rail interaction and the gear-rack meshing. The results show that due to the gear-rack meshing the meshing stiffness and the meshing force are subject to the periodical variations and the gear-rack meshing can significantly affect the wheel/rail interaction, especially in the presence of track irregularities. The driving mode that the gear wheel is installed on the wheelset axle through a hollow shaft is considered as a more practical design for the rack vehicle.

In order to compare the differences in vibration before and after wheel re-profiling and assess the vibration impact of train under full-load and empty-load condition, the field vibration measurement was conducted on an underground metro track components (including rail, sleeper, and track-bed) by using a specific testing car. The results indicate that wheel re-profiling is effective in reducing track vibration, within the frequency range of 31.5–1250 Hz, the vibration acceleration levels of the track after wheel re-profiling were notably lower than those prior to re-profiling and the vibration acceleration levels of the rail, sleeper, and track-bed decrease by 4.7 dB, 6.6 dB, and 6.7 dB, respectively. In the frequency domain, the characteristic peak frequencies of the three track components, whether under full load or empty load, align closely with the frequencies associated with track irregularities. Full-load condition primarily affects the vibration acceleration at lower frequencies, with minor influence on higher frequencies. The vibration acceleration levels of all three track components are higher under full load than empty load. Additionally, under full-load condition, the transmission loss from the rail to the sleeper increases, while the transmission loss from the sleeper to the ballast remains nearly constant. The results of vibration acceleration levels obtained from routine vehicle operations validate the limited impact of axle load on track components vibration.

The debris detection characteristics of the inductive wear monitoring are researched by the method of combining theoretical research and simulation analysis in this paper. The mathematical model of the change in inductance is established based on the change in the coil magnetic field by the abrasive particles. By the COMSOL simulation software, the physical model of the three-coil wear monitoring is established, and the influence of the coil structure parameters on the output induced electromotance is compared and analyzed, resulting in the optimization of the coil parameters. For metal particles with different properties and sizes, the changes in the induced electromotance during the process of passing through the coil are analyzed, obtaining the mapping relationship between each particle size and the output induced electromotance. The simulation results show that the output voltage corresponding to the particles is related to the coil structure parameters, and the larger the particle size, the larger the output voltage. Finally, through experiments, the designed sensor coil structure has been proved to have a better detection effect on metal particles, realizing the detection of ferromagnetic abrasive particles above 100 µm and non-ferromagnetic abrasive particles above 200 µm.

The coil structure of the inductive wear debris sensor plays a significant role in the effect of wear debris detection. According to the characteristics of LC parallel resonance, the capacitor and coil are connected in parallel to make sensor coils in the LC parallel resonance state, which is beneficial to improve the ability to detect wear particles. In this paper, the mathematical model of output-induced electromotance of the detection coil is established to analyze the influence of the structure on the detection sensitivity and enhance the sensor’s current rate of change to the disturbance magnetic field, which is essential to resist noise interference. Based on the coherent demodulation principle, the AD630 lock-in amplifier is applied to the test platform to amplify and identify weak signals. In addition, experiments are designed to test the output signals of debris under the condition of different original output voltages of the sensor with a parallel structure. Meanwhile, the near-resonance state of the detection coil with LC parallel circuit is tested by output signal information. Results show that the sensor detection sensitivity will be effectively improved with the LC parallel coil structure. For the sensor structure parameters designed in this paper, the optimal raw output amplification voltage for abrasive particle detection is 4.49 V. The detection performance of ferromagnetic particles and non-ferromagnetic particles is tested under this condition, realizing the detection ability of 103.33 μm ferromagnetic abrasive particles and 320.74 μm non-ferromagnetic abrasive particles.