Study On Vibration Behaviourand Fatigue Failure Of Gearbox Housing Of High Speed EMU

The gearbox of high-speed EMU is the key component of the power transmission between traction motor and wheel-set,which plays a significant role in ensuring the power transmission and the safety of the EMU in operation of high-speed.However,there are few service ability problems in the gearbox system of power decentralized vehicles such as subway due to the lower running speed,so there was relatively little research on these problems.With the increasing running speed of high-speed EMU,the continuous increase of mileage in service and the increasing complex operating environments,there are some problems in the gearbox system,such as oil leakage,lubricating oil blackening,a few of other materials in the gearbox housing and cracking of the gearbox housing,which seriously threaten the safety of high-speed EMU.Based on the background that a large number of cracks occured in the gearbox housing of high-speed EMU during actual service operation,the vibration characteristics and fatigue damage of gearbox housing of high-speed EMU were studied,The main research contents are as follows:(1)By programming Uff programs with Matlab software to generate the data format that can be recognized by LMS Test.Lab software.The spectrum characteristics of different types of working conditions were studied,for the service test data of the two types of gearbox housings of type A and type B under different working conditions,and the vibration characteristics and cracking reasons of the two types of boxes were analyzed.It is proposed to analyze the influence of factors such as line type,vehicle speed and wheel tread wear on the vibration of the gearbox box.Based on the line service test data,consider the high-speed EMU running in the over-phase zone,uphill and downhill,over tunnel,Start acceleration and decelerate parking and curve track and other line conditions,focus on researching the response trends of speed changes of high-speed EMU to the vertical and lateral accelerations of gearbox housing;In the case of similar operating conditions,the vibration characteristics gearbox housing with the new repaired tread and the worn tread were compared and analyzed;researching the time-frequency characteristics of the vibration of the type B gearbox housing with improved structure and the axle box,obtaining the influence sources component of the dynamic response frequency of the gearbox housing,it is proved that there exists polygon on the worn tread,and the local natural frequencies of the gearbox can be excited by polygon wheel-rail excitation frequencies and generated covibration phenomenon.Therefore,it is suggested to strengthen the research on the formation mechanism of wheel polygons,and propose effective measures to delay or suppress the high-order wheel polygons,and minimize the influence of high-order polygon excitation on the vibration of the gearbox housing.(2)Based on the small roller high-frequency excitation test bench,the vibration characteristics of the gearbox case under different vertical loads and speed conditions are studied.It is found that the 573 Hz local natural frequency resonance in the type B gearbox housing which under the disturbance of the 20-step wheel polygon wheel is consistent with the conclusion that there is 580 Hz local natural frequency resonance in the type B gearbox housing in the service line test,that is,the line test result is reproduced in the small roller high frequency excitation test bench;the dynamic stress was calculated by combining the dynamic strain measured under the test conditions,and cumulative damage evolution of the dynamic stress on the gearbox housing under different vertical loads and speed grades was studied by means of the method rain flow counting and the law of linear Miner.(3)Based on the established rigid-flexible coupling model of high-speed EMU,the vibration characteristics of gearbox housing was studied.The rigid-flexible coupling dynamic model of EMU with the gearbox housing and the wheel-set as flexible bodies and the sleepers and rails as elastic bodies,and the other components as rigid bodies was established,and the reliability of the model was verified.Considering the different running speeds,different orbits,and the rail wheel excitation with different polygons and wheel diameter difference,the vibration acceleration characteristics,vibration transmission characteristics and dynamic stress response characteristics of the gearbox box are simulated.(4)Based on simulation analysis,research conclusions on bench tests and line tests,considering various loading conditions that may be encountered on the service lines,the working conditions of the gearbox housing under the supernormal loads,operating loads,impact loads and random vibration loads in the simulation analysis are formulated.According to the relevant standards,a more reasonable load and constraint boundary condition for highspeed EMU gearbox simulation is proposed,and the fatigue failure evaluation of the gearbox housing model was carried out.