Material Analysis of a Locking Bar with Failure

The external locking device of a railroad switch is an important installation to lock switch rails and stock rails or wing rails by a switch machine. A locking bar can link with the actuator pole of the switch machine to finish switch and act in concert with the locking hook to lock the system. It is required adequate mechanical properties such as yield and fatigue strength. The text analyzes macro-feature of the fracture of a locking bar with failure and gets the conclusion that the locking bar fatigue fractured under alternating load. Metallographic structure and hardness of the material are also examined and found that quenching tends to be overheated with its poor hardenability. The solution is to improve the heat treatment method and increase the fatigue strength.