High Frequency Tyre Vibrations

Licentiatavhandling, 2002

High frequency (above 1 kHz) noise generation from the tyre/road interaction is still not fully understood and accurately modelled. Two noise generation mechanisms previously suggested in the literature are reviewed: air pumping and noise generation cased by adhesive effects between the tyre tread and road surface. These mechanisms are located in and near the tyre/road contact zone, and a deterministic description of these mechanisms requires a tyre model that is able to describe the high frequency behaviour of the tyre, including local deformation in both the radial and tangential directions. A three-dimensional two-layer plate tyre model based on the elastic field equations is suggested as a model that would fulfil these requirements. This model was developed earlier [1], and is now extended to allow for comparison to mobility measurements on real tyres. The overall agreement between the model and measurements is surprisingly good in view of the simplicity of the model. However, some limitations of the model are also presented. The tyre model is used in two investigations focusing on the dynamic behaviour of tyres in both the radial and tangential directions in the frequency range from 50 Hz to 4 kHz; (i) investigation of the dynamic behaviour of smooth and patterned tyres at high frequencies for both radial and tangential directions, and (ii) a parameter study investigating the relation between internal tyre parameters and the response at the outermost surface. It was found that the radial point mobility is greatly influenced by properties of the local deformation at high frequencies and/or small excitation areas. The tangential point mobility is affected by local deformation in almost the whole frequency range. Hence, it is mainly the properties of the tread cap and the pattern that determine the response at high frequencies and in the tangential direction. The radial response is determined by the combined properties of the belt and the tread cap at medium frequencies, while it is the dimension and the pre-tension in the plies that determines the low frequency response.