The influence of modelling parameters on the simulation of car tyre rolling losses and rolling noise

Licentiate thesis, 2012

Due to legislative changes within the EU there is an increased demand for improvement in car tyre rolling resistance and noise generation. Yet, apart from empirical data based on measurements, there is little information concerning the relationship between rolling resistance and rolling noise generation. The purpose of this work is to establish a simulation framework which allows to explore the underlying physical processes connecting both areas. Special emphasis is put on the development of an accurate and efficient condensation procedure for the estimation of the necessary tyre input data from detailed design data available to the manufacturer. The method is exemplified by the derivation of the input deck for a 175/65 R14 tyre which was previously not implemented in the modelling tool. For the simulations a waveguide finite element model of the car tyre is combined with a non-linear 3D model of the tyre/road contact to simulate the structural dynamics of a tyre rolling under steady-state conditions on a real road. Rolling resistance is calculated based on the power input into the tyre while the velocity field on the tyre surface is used to determine the radiated sound pressure based on a boundary element method approach. The applicability of the approach is shown by calculating rolling resistance and sound radiation for an initial setup of modelling parameters. In the further course of the study the influence of a variety of modelling parameters on the outcome of the rolling loss and rolling noise simulations is investigated. A number of key parameters for the simulation of one or both of the quantities are identified. It can be shown that especially the contact stiffness and the geometry of the BEM mesh are crucial parameters for the rolling noise simulations. Some remarks on the required quality of tyre input data are made. Further results show that it is not generally possible to relate variations in input and transfer mobilities to changes of rolling resistance or rolling noise and vice versa.