Squeal noise of rail-bound vehicles influenced by lateral contact position

A frequency domain model has been developed to describe squeal noise of rail-bound vehicles generated by unstable lateral creepage between wheel and rail. The model is based on a combination of existing models for contact mechanics, contact dynamics, wheel dynamics and rail dynamics, which are transformed into the frequency domain. The relation between friction coefficient and lateral creepage is linearized to allow frequency domain calculations. This enables fast calculations and enhances insight into frequency-dependent phenomena relating to squeal. In addition to existing models, the variation of the normal contact force is implemented in the model. This addition to the model is essential to explain several effects. One of these effects is the influence of the lateral contact position on the wheel tread on squeal noise; squeal noise by lateral creepage only occurs for a certain contact position interval. A laboratory test rig (scale 1:3) was designed to validate the model. Two measurements will be presented in this paper. The friction coefficient of the rolling contact is measured as a function of lateral creepage, for cases with and without squeal (but with the similar contact surface conditions), giving different results. The required wheel damping to prevent squeal noise is measured as a function of the lateral contact position. The test rig has been used for model validation and will be used to evaluate and optimize particular measures against squeal noise. The model can be used as a design tool for measures against squeal noise by lateral creepage.