Analysis On The Strength And Fatigue-life Prediction Of Standard High-speed EMU Gear Box Housing

ABSTRACT:As the key component of high speed train transmitting torques and driving locomotives, gearbox, more specifically its security and stability, would have a direct effect on the reliability of the vehicles in motion. However, due to its complicated structure and the poor operating conditions, the gearbox systems tends to end up with many problems, such as the permeability (leakage), the high temperature of gearbox oil, the crack in gearbox-body and so on. These problems, would seriously threaten the safety of passengers.This paper conducted research on the fatigue strength and the vibration properties of gearbox under the standard load of EN 13749 and the actual load. Meanwhile it acquired the real load through the tracking test and made the fatigue life predictions according to the equivalent damage theory, providing reference comments for design, detection and maintenance. The analysis in details is as follows:Primarily, the simulating analytical method for gearbox-body was conducted. The fatigue strength analysis was made for gearbox-body under standard load, according to which the strength of gearbox-body satisfies the requirements in good casting conditions. Meanwhile, the stress response were obtained under the standard load, providing the references for experiments.Secondly, based on the stress-time history data acquired in tracking test, the analysis of dynamic load strength were conducted for gearbox-body under different speed levels. By studying the time domain and frequency domain features in different running conditions, conclusions can be drawn that the extreme value of amplitude, the extreme value and the equivalent tress all augmented as a result of the increasing velocity and the energy of measuring point as well as the corresponding frequencies are linearly related to velocity. Moreover, this linear-related equation was deduced, which could be used to predict the possible high-energy frequencies in different velocities.Then both time domain analysis and frequency analysis were conducted for the real acceleration signals. In time domain, the relation between vibration load and velocit was studied, according to which it could be observed that the increase of equivalent accelerations is relatively large and the vibration is obviously fiercer while the velocity is higher than 340km/h. In frequency domain, the vibration energy, velocity and frequency are analyzed. According to the analysis, the frequency 46Hz is the intrinsic property of the vibration of vehicles. Meanwhile, the frequencies won’t change despite different velocities, but the energy in corresponding frequency will augment with the augmentation of velocities.Finally, the fatigue life prediction was made for gearbox-body based on the actual load and standard BS_EN-1999-1-3.The large stress positions which are difficult to be tested in gearbox-body were derived on the basis of the corresponding relation between the finite element method and the actual load equivalent stress, and finally the fatigue life was also predicted for gearbox-body in different casting conditions according to the equivalent damage theory.