Fatigue Crack Failure Analysis of Wrought Steel Railway Wheel with Web Plate Hole

摘要

The fatigue crack failure analysis of a broken wrought steel railway wheel with web plate hole has been investigated to find the failure causes. The macro-appearance analysis of the broken part show that the crack belongs to typical fatigue crack initiated at the inner side of the web plate hole, while the macro and microfractographic features of the broken wheel do not show any evidence of the occurrence of a fatigue mechanism, indicating that the failure is not material defect but its structural feature and the formidable operation conditions. Therefore, the paper also analyzed the wheel with finite element method under different operation conditions to find the failure cause. According to the finite element analysis results, the existence of the web plate hole causes the structural discontinuity generating severe stress concentration under mechanical load. An approximate zero-pressure cycle is generated at the inner side of the web plate hole under mechanical load during a complete rotation of the wheel. And under different braking conditions, especially under long and big grade braking, high thermal tensile stress is generated in the web plate. At last, the operation conditions leading to the crack generating were analyzed by fatigue limit diagram. The analysis results show that the couple of mechanical cyclic stress and thermal tensile stress during braking condition is the main cause of the fatigue crack.