RESUMO
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.
RESUMO
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.
Assuntos
Amplificadores EletrônicosRESUMO
A three-dimensional electrode system for electrochemical oxidation was developed in which Cu-Ce composite oxides supported on gamma-Al2O3 and granular activated carbon were packed between the main electrodes. X-ray diffraction (XRD) and scanning electron microscope (SEM) were used to characterize the particle electrode. The results showed that the particle electrode had good electrocatalytic activity and stability for the degradation of landfill leachate. When pH value of landfill leachate was 7, the voltage was 10 V, and air-flow was 0.04 m3/h, the removal rate of COD and NH4+-N can reach 87.8% and 45.4%, respectively. The treatment effect of electro-heterogeneous catalytic process was greatly higher than that of electrochemical oxidation process in two dimensional flat reactor and bipolar packed bed cell. In addition, CuO-CeO2/gamma-Al2O3 was active even after it was reused twenty times. It was found that landfill leachate degradation followed a pseudo-first-order reaction kinetic model, and the removal of pollutants under these operating conditions could be mainly attributed to the direct oxidation effect in the electro-heterogeneous catalytic reactor.