The sources of noise from a vehicle can be separated into four main areas, the engine, exhaust, air intake and the noise produced as a result of the tyres rolling in contact with the road. Reductions in the former sources have been significant and it is now recognised that the tyre / road interaction noise is dominant for constant speeds for almost all types of driving. It is also a significant contributor during acceleration and braking.
The noise which is radiated from the tyre surface is produced by several mechanisms, including the vibration of the tyre surface, vibrations of the tread blocks and resonances of the air cavities in the contact patch between the tyre and the road surface.
In order to investigate the noise produced by the tyre rolling over a rough surface, detailed information must be known about how it responds to excitation. A methodology for determining the vibration characteristics of the tyre belt has been successfully completed. This tyre belt, located between the sidewalls and made up of several different layers of materials, has been modelled as a three dimensional viscoelastic multilayer structure, including the curvature of the tyre surface, the significance of each individual material layer and its properties, for a wide range of excitation frequencies.
The displacement of the tyre surface has been determined for the case where a force is applied normal to the surface and tangential to the surface, using only design data. Spectral decompositions are used to identify mode shapes and resonances in the frequency domain rather than the time domain.
Other mathematical models have been used to determine the vibration of the tyre belt using simplifications to obtain shell and flat bending plate models. Deriving parameters for these models is usually done empirically with reference to data collected from experimental measurements, or estimations are made. Advantages of this method are that experiments can be performed on real tyres and parameters obtained without needing to know exact details of the construction of the tyre. However, for every potential tyre design to be investigated, a physical tyre must be made, at expense and time to the manufacturer. It also does not allow any detailed physical insight into the stress and displacement in each layer.
A method has been determined to find these simplified plate parameters by comparing the response from a simplified bending plate to the full three-dimensional viscoelastic tyre belt model, using a multivariable optimisation technique to minimise any differences, without requiring access to experimental data.
These parameters are used in a finite width model of the tyre, which takes into account the effect of the sidewalls. Comparisons can then be made between this model and experimental data. Source & Details