The simulation of car and truck tyre vibrations, rolling resistance and rolling noise

Doktorsavhandling, 2014

The road transportation sector places a severe burden on the environment in the form of CO2 emissions and road traffic noise. Both of these environmental prob- lems can be related to car and truck tyres. In spite of this, there is a lack of suitable simulation tools for the prediction of rolling noise and rolling resistance and the investigation of the relevant physical processes behind these two quanti- ties. The purpose of this thesis is to establish a simulation framework which allows for the exploration of the underlying physical processes for rolling resistance and rolling noise. For this, an acoustical tyre/road interaction model aimed at calcu- lating rolling noise is extended and combined with a module for the calculation of rolling losses. The proposed tool consists of a waveguide finite element model of the tyre, which is combined with a non-linear three-dimensional tyre/road contact model to simulate the structural dynamics of a tyre rolling under steady-state con- ditions on a real road. Rolling resistance is calculated based on the input power 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. Tyre vibrations, rolling noise and/or rolling resistance are calculated for different car and truck tyres and a wide selection of road surfaces. There is good agreement with mea- surements for both quantities, making this the first tool which can be successfully used for the simulation of both rolling resistance and rolling noise. The method is especially suitable for extended parameter studies because of its numerical ef- ficiency. A number of important research questions are investigated. It is shown that rolling resistance can be split into two parts: one part originating from the large-scale tyre structure deformations, and another part arising from small-scale tread indentations which are highly dependent on road surface texture. An inves- tigation of the free wave propagation on a truck tyre indicates that the structural differences between car and truck tyres lead to some differences in the vibrational behaviour. Additionally, it is investigated how well a certain road surface section is represented by a limited number of road surface scans. It is shown that for most applications and surfaces a minimum number of scan lines from different sample locations are needed if simulation results should be representative of the whole surface.