A HIGH FREQUENCY RANGE TYRE MODEL BASED ON TWO COUPLED ELASTIC LAYERS

The dominating noise source at speeds greater than 30 - 50 km/h is the car tyres. In order to achieve a reduction of the traffic noise the tyres have to become quieter. To reduce the tyre noise, a deep understanding of the noise generation mechanisms is of major importance. To be able to predict the sound generation from a specific tyre, a complete method for calculating the radiated sound from a rolling tyre has been developed by Kropp. The method combines three different modeules: (1) A tyre model, where the dynamic properties of the tyre are considered; (2) A contact modeI, where the non-linear contact forces during the rolling process and the corresponding vibration velocities on the tyre are calculated; and (3) A radiation model, where the sound radiation from the tyre due to the velocity field on the tyre surfacc is calculated. One major drawback with this scheme is the contact model where only the radial part of the contact forces is included. During the rolling process the tyre will be exposed to tangential contact forces mainly due to three reasons: (1) Geometry, the tread blocks enter the contact zone at an angle relative to the road. The contact force can be divided into one radial and one tangential component; (2) Friction, due to velocity differences between the vibrating tyre including tread blocks and the road surface, time varying tangential friction forces will act on the tread block; and (3) Roughness, the roughness of the road surface leads to a variation of the radial contact forces, which will also influence the tangential friction forces. In order to improve this contact model the dynamic tyre model has to be able to include the reaction to both radial and tangential contact forces. For the covering abstract see IRRD E104312.