An investigation of fatigue crack growth behavior of UIC 54 profile in high speed railway applications

Abstract

The safety of wheels and rails is a greater concern for the Malaysian railways Keretapi Tanah Melayu and manufacturers of the railway network. The rolling contact fatigue (RCF) is a growing problem due to increase of the high speed train operation in Malaysia and increased of load cycle. The RCF is defined as a damage that occurred due to the change in the material microstructure which contributes to crack initiation followed by crack propagation under the influence of time-dependent. The typical cracks originating at the running surface is called as head check. The transverse cracks leading to the eventual fracture of the rail. As well as the crack growth rate is higher, it caused the crack to propagate faster and initiate the sudden rail failure at any time. In this study, numerical analysis of stress–strain characteristics of three dimensional (3D) wheel-rail contact was successfully carried out by ANSYS Workbench 14.5. Apart from that, this study focuses on the fatigue strength and fatigue crack growth (FCG) of UIC 54 profile. The fatigue strength and FCG study were coordinated with the dog-bone specimen (ASTM E-466- 15) and compact tension (CT) specimen (ASTM E-647-15), respectively. The S-N curve was plotted from 7 data of the dog-bone specimens to evaluate fatigue strength with a constant stress ratio 0.1, and variable in applied stress levels. In addition, the rail profile of UIC 54 fatigue strength was validated with simulation result by ANSYS Workbench 14.5. The simulation works were executed with dog-bone specimen model according to the experimental applied stress level. Meanwhile for FCG the study was conducted with the CT specimens with a variable in stress ratio of 0.1, 0.3 and applied loads of 16 kN and 13 kN. The material crack growth rate for UIC 54 profile is obtained from Paris– Erdogan relationship C and m. The maximum von–Mises stress result for the wheel and rail contact was obtained higher at rail gauge corner region and it’s exceed the yield strength limit (533 MPa) of UIC 54 profile. Furthermore, the equivalent plastic stress result reveals that most of the plastic deformation occurs at the rail gauge corner region, on the contrary almost very small plastic deformation occurs at the wheel. The overall hardness measurement for used rail obtained was 37.9 % greater than unused rail. The hardness value for P1 (used rail) indicates that rail gauge corner region was affected by high contact stresses and plastic strains.