Fatigue strength and residual stress evaluation of repair welding of bogie frame for railway vehicles

Abstract

The bogie frame of a railway vehicle is an important component that supports the load of passengers and cargo. Bogie frames are manufactured using welding owing to their complex geometry. Cracks occur in weld zones during driving owing to cyclic fatigue loading. Cracks can be repaired using various methods. In the case of bogie frames, cracks are removed and then repair welding is performed using gas metal arc welding. The fatigue characteristics of repair welding vary depending on various conditions, such as materials and repair welding methods. In this study, the fatigue characteristics of SM490A, a material used in railway vehicles, were evaluated for welding and repair welding. Welding specimens and repair welding specimens were prepared and fatigue tests were conducted. In addition, finite element analysis (FEA) was conducted to evaluate the residual stress change. The fatigue test results showed that the S-N curve of the repair welding specimens was lower than that of the welding specimens. This is because the residual stress of the repair welding specimen is greater than that of the welding specimen. The residual stress measurement and FEA results showed that the maximum residual stress was 251 MPa for the welding specimens and 340 MPa for the repair welding specimens, indicating a significant difference. In addition, the FEA results for repair welding revealed that the maximum residual stress increased as the welding width increased and the forward welding pass was used in the welding direction, confirming that minimizing the repair welding width and using the reverse welding pass is beneficial for fatigue characteristics.