Evaluation of the metrological characteristics of an instrumented wheelset for the measurement of wheel-rail contact forces

The actual European regulations in matter of rail vehicle homologation prescribe to measure not only accelerations but also contact forces exchanged at wheel-rail interface, in order to state the level of running safety, track loading and vibration behaviour. It is important to point out that the standards do not prescribe any specific method to measure forces, nevertheless define any metrological requirement of the measuring system. Aim of this paper is to investigate the metrological properties of a dynamometric wheelset in order to determine the associated measurement uncertainty and to verify its readiness in the range of frequencies where the force analysis have to be performed. With reference to a specific instrumented wheelset, the calibration procedure was performed using a dedicated test-rig developed in the laboratories of the Department of Mechanical Engineering - Politecnico di Milano. The test-rig allows a static calibration of the system. Dynamic tests have been performed, imposing a random or an impulsive excitation to the wheelset, in order to define the bandwidth of the measuring system.