Analysis and redesign of bolster beam of the bogie frame of a locomotive

Locomotives are the back bone of the transportation system in any country. Locomotive mainly consists of engine and control assembly placed on the under-frame which in turn rests on two bogies. Cracks are reported to occur in the bolster beam of the bogie frames in one of the designs of locomotives in service. Cracks are treated by welding and locomotive is resent in operation but cracks appeared again on some other locations beside the welded portion. In order to investigate the reasons for crack initiation; data regarding rail track and its quality, routes and severity of operation and drawings of the locomotive is collected. Finite element analysis is then performed first for the existing design of the locomotive in use to find the reason for the crack. Curvature and small radii are concluded the main reason of crack initiation and propagation under continuous oscillatory lateral movement on straight track and lateral forces during turning. In addition, removal of stiffeners from certain locations concluded ease of manufacturing. Use of friction modifiers is recommended to reduce forces generating cracks. Design optimization is performed using detailed finite element analysis for minimum weight and safe stress against fatigue.