Reliability Evaluation And Failure Mechanisms Of EMU Wheel Under Low Temperature

The wheel of high-speed EMU is the most important part of locomotive vehicle,with the functions of bearing weight of train and moving train.It is the key part to the EMU safety operation.Nowadays,the WSP which is a antiskid product,has been applied on the body of every EMU,but the EMU wheel still frequently locked in the daily operation.As the EMU shoud suffers cold,rain,ice and other condition under low temperature,which leds to more frequent sliding of wheel and rail.o develop fatigue reliability technology researches on fatigue of the EMU wheel under low temperature will be of great importance.The failure mechanism will be studied from the aspect of sliding of wheel and rail.The finite element model of transient rolling contact and crack propagation were established to study the fatigue reliability of EMU wheel under low temperature.The contents are as follows:1.With rolling and local heat treatment way,the wheel has a gradient characteristics performance.Wheel spoke and rim has the same material,but has different mechanical property.According to some standards,we make standard cylinder sample pieces from spoke and rim and take a series of tests to get material mechanical properties of wheel spoke and rim under-40? condition,such as yield strength,strength of extension,fatigue strength,S-N curve,and so on.2.With thermo-mechanical couple technology,the finite element model of wheel/rail sliding was established to study the temperature field and stress field of wheel/rail.Based on the finite element analysis of wheel/rail friction and experimental data of the phasetransformation in wheel steel,the mechanism of wheel thermal fatigue under low temperature was simulated.And the affection on phase transformation zone in wheel tread has been discussed by the changes of the environment temperature and friction coefficient of wheel/rail.3.The finite element model of transient rolling contact was established to study the stress field about the area of wheel indentations.The affection on max Mises stress of wheel has been studied by the changes of the speed of train.Evaluation the safety of spokes and rim region fatigue strength by the Haigh-Goodman curve,and analysis of the reliability of the fatigue strength by the stress-strength interference model.4.According to the quantitative techniques,the wheel indentations was equivalent to a semiellipse crack on the surface of wheel tread.A finite element model of crack propagation was established to calculate the stress intensity factor.Based on the method of damage tolerance,assessment of wheel fracture brittle include by low temperature at the current maintenance plan.