Research On Fatigue Crack Initiation And Propagation Of Gearbox Material For High Speed Train Based On In-situ Fatigue Method

Gearbox is a part of the critical components of high-speed train power transmission system.The reliability,safety and stability of its service will directly affect the normal operation of high-speed trains.During the operation of high-speed trains,the gearbox is needed to withstand complex loads such as shock caused by changes in motor torque and vibrations under wheel/rail excitation.Its service environment is very harsh,and fatigue damage is easy to occur during use.Therefore,studying the fatigue crack initiation and propagation law of gearboxes has crucial theoretical significance and application value.This paper analyzes the stress conditions and fatigue crack initiation and expansion of a domestic 380 km high-speed train gear box during use.The main contents of this thesis are shown as follows:(1)A three-dimensional modeling software Solid Works was used to create a box model,and the strength analysis was performed using the finite element analysis software Workbench under static and fatigue loads,and the stress-strain distribution cloud maps and displacements in various directions under different types of loads were determined,thereby determining Dangerous points and dangerous sections of the gear box structure.The results show that under the static and fatigue loads of the box,the maximum stress position appears in the left area of the drive gear bearing seat at the output end of the box,and the maximum displacement appears in the rear area of the tank at the output end of the box.The maximum strain It appears in the left side area of the connection position of the box body and the C-shaped bracket and the lower left side area of the drive gear bearing seat at the output end of the box body.Therefore,it decides to conduct sampling and analysis in these areas.(2)Sampling from the gear box using wire cutting technology,using inductively coupled plasma emission spectroscopy(ICP-OES),X-ray diffraction(XRD)phase analysis,and scanning electron microscope(SEM)combined with energy dispersive X-ray Spectrometer(EDS)is used to inspect the microstructure of the box material.The results are shown that the microstructure of the cast aluminum alloy gear box material for high-speed trains consists of ?-Al,eutectic Si,iron-rich ? phase,and Mg2 Si phase.(3)An in-situ fatigue test and synchrotron radiation X-ray tomography test were used to analyze and study the fatigue crack initiation and propagation mechanism of gearbox materials.Test results show that the presence of second phase particles in the material will reduce the fatigue performance of the cast aluminum gearbox.When the material is subjected to external stress,the brittle second phase particles are more likely to emerge from.The micro-crack coalescence caused by the fracture of the second phase particles accelerates the initiation and propagation of fatigue cracks.Therefore,the adverse effect of the second phase particles on the fatigue life can decrease by appropriate microstructure adjustment.