Research on the fatigue strength assessment methods of EMU wheel

A new fatigue strength assessment method of EMU wheel is developed and presented. This method combines the principal stress method with the Crossland fatigue criterion to solve difficulty encountered in determining the key parameters and choosing a simpler algorithm. According to the physical properties that crack initiation is usually perpendicular to direction of principal stress, principal stress method is first applied for the wheel strength assessment. Then the Crossland fatigue criterion is used as a supplement when the safety factor is about 1.0 ~ 1.1 derived from the principal stress method. Given the condition that wheel's load condition is mainly bending, an amendatory Crossland fatigue criterion is put forward in the paper. It describes the wheel's strength status with the bending fatigue limit, which can solve the difficult problem that it is difficult to obtain the key parameter of full size's torsion fatigue limit of wheel's web with the original Crossland fatigue criterion. A fitting method of S-N curve is given by considering the effect of size and surface state for EMU wheel's web. The fatigue lives of EMU wheels of CRH1, CRH2 and CRH5 were calculated by using the new assessment method. The analysis result shows that the new assessment method is available for all kinds of EMU wheels. It also shows that the new assessment method can ensure the wheel's design plan with sufficient safety margin in some degree.