| Rim crack is a common form of wheel fatigue failure.With the increase of train speed and load,the continuous crack growth will cause deep peeling of wheel tread and take harm to the railway safety.This paper studied the crack growth characteristics and fatigue life of high-speed wheel rim.Firstly,the fatigue fracture performance of ER8 high-speed wheel rim is studied,and the fatigue growth threshold and crack growth rate of mode I crack and I-II mixed mode crack are obtained.The propagation direction of the mixed mode crack is measured.The analysis results show that the propagation angle of the composite crack of wheel steel is basically consistent with the predicted value of the maximum circumferential stress criterion（MTS）.The finite element simulation software FRANC3D is used to simulate the crack growth process of I and I-II mixed mode of wheel steel samples,and the crack growth angle is calculated.The validity of the crack simulation method is verified by comparing the simulation results with the test data.Furthermore,the variation of the stress intensity factor at the crack tip with the crack growth distance is simulated.A three-dimensional wheel rail rolling contact model with wheel rim crack is established,which is based on the test data.The propagation path and stress intensity factor of mixed mode crack of wheel rim with different initial angles are simulated and analyzed.The results show that the angle of inclined crack increases with the increases of equivalent stress intensity factor range?Kequ.Under the wheel-rail rolling contact load,the crack propagation behavior is mainly in shear mode.I-type stress intensity factor is negative so the open crack is in the closed state.II and III-type stress intensity factors are both positive and the type II stress intensity factor is the main driving force of crack growth.The crack propagates along the direction parallel to the tread,and the crack growth surface has three-dimensional characteristics.The influence of wheel wear on the crack propagation characteristics and life of wheel rim was studied.The change rule of stress intensity factor at the crack tip of worn wheel rim is analyzed.The results show that the equivalent stress intensity factor increases when the diameter of worn wheel decreases.The crack growth life under the condition of wheel flat and polygon abnormal wear is calculated.When the train speed is 350km/h,the initial crack size is 0.5mm,the results show that the crack growth life decreases with the increase of wheel flat length,and the crack growth life corresponding to the 50 mm wheel flat length is the lowest 9.1x106.With the increase of polygonal order of wheel,the crack growth life of the 10th order polygon is the lowest 3.1x106.The research provides guidance for wheel design and maintenance cycle,which is helpful to improve the fatigue life of wheel and ensure the safety of high-speed train. |
