Selection and parameter optimization of bogie locking mechanism for variable gauge locomotives

Variable gauge locomotives require bogie locking mechanisms that are both structurally simple and reliable. This paper presents a locking mechanism that leverages the gravity of the wheelsets for unlocking and supports two locking modes: spline and flat key. The selection of locking modes and materials was guided by the theoretical static strength checks of the keys and finite element analysis of the locking mechanism. The flat key option was selected as the study object due to its superior performance compared to the spline option. An analysis was conducted to assess the influence of different magnitudes of interference between the flat key and the axle box body, as well as the chamfer size of the flat key. The results show that the flat key option is lower in the equivalent stress than the spline option and convenient in processing and disassembly, resulting in reduced maintenance costs. Furthermore, flat key locking mechanisms made of C-grade steel exhibit the lowest equivalent stress. The maximum equivalent stress shows a trend of first flattening, followed by a decrease, and then an increase with increasing magnitudes of interference. The position of the maximum equivalent stress is found to be associated with the magnitudes of interference. Additionally, choosing an appropriate chamfer size for flat keys can effectively alleviate stress concentration and reduce equivalent stress. This locking mechanism, characterized by its simple and reliable structure and a simple and convenient unlocking-locking process, provides a reference for the design of variable gauge bogies.