Damage Identification on the Leaf Spring of a Railway Freight Wagon—Findings from Snap-Back Experiments with Transient Excitation

Abstract

Structural Health Monitoring (SHM) systems for structural parts of freight wagons are subject to special conditions. An important task of those systems is to detect damage to the leaf springs of the wagons. In such a case, the damaged wagons must be removed from the train and repaired at the next opportunity. However, the framework conditions for such SHM systems for wagon suspensions are a challenge in some other respects: on the one hand, the commercial framework is very tight which prohibits the use of expensive technology. The hardware required for each wheelset must not only guarantee the operation of the SHM algorithms, but also the following functions: data storage, communication with the other wheelsets and a control center somewhere on the rail network, data management and system control and power supply. All tasks have to be performed under extreme environmental conditions like rain, snow, ice, heat, shock loads, dust, etc. Because of these requirements slim and robust SHM algorithms have to be developed. Based on these requirements, the proposed paper deals with the damage detection at the suspension of a railway freight wagon and firstly reveal, that the measured accelerations changes with the damage in a characteristic way. The authors show that the damage of the suspension is accompanied by a reduction in spring energy in the measured signals and a shift of the higher vibration modes. In this context, the paper has no pretense to develop new methodologies for damage identification but the simple findings from the experimental tests can be useful for the design of SHM systems for railway vehicles. At the end, a simple SHM approach for a low number of sensors with practically positions at the wagon is proposed.