Defer effects of crack propagation of bogie

With the enhancement of the speed and the load capacity of rail vehicles, the running conditions of bogie frame and the main supporting parts of rail vehicle become worse.In order to reduce the interaction force between rail and wheel, the weight of the frame has to be optimized.Thus the fatigue strength of the bogie is of concern.The fatigue experimental results of a high speed train show that the crack propagation of the frame slow down under the cyclic loads.The concept of relaxation of residual stress under cyclic loads and open and close of crack are utilized to analyze the effects of crack propagation.The analysis shows that the main reason of the crack propagation slow down of the frame is the relaxation of the residual stress under the cyclic loads.Crack close also affects the crack growth greatly.The maximum allowable length of non propagation crack is calculated under the given configuration and cyclic loads.