The analysis of a damaged component from the connection system of the wagons

Abstract

The operation of passenger trains in different continents is still differentiated by different wagon connections systems. The predominant wagon connection in North America and Australia is the autocoupler system. The system of draw hooks and buffers is now rare. In Europe, draw hook and buffer systems are still in wide use. In particular, the majority of passenger trains in Romania have wagons connected by draw hook and buffer systems. This paper presents an unusual situation for analysis of a damaged component of draw hook system and where has been lost the basic information about the causes of failure. Due to the lack of information, the analysis has a high degree of assumptions, being based on failure scenarios. The broken component is a link plate made of forged steel. After an initial examination of the fracture surface, was observed the existence of a structural defect in the material from which was initiated a fatigue crack. The analysis involves an experimental evaluation of the mechanical properties of the failed component material, followed by the modeling of the behavior of connection system according to the position where is mounted on the train. Based on the mode of fatigue crack propagation, correlated with the loading level of the connection system, different scenarios have been made about the time of propagation. Because important information about the failure causes was lost, the analysis was performed taking into account almost all factors that could influence the fatigue crack propagation.This analysis came in completing the expertise done by specialists in Traffic Safety on the Railways.