Modelling the vibrations on a rolling tyre and their relation to exterior and interior noise

For most modern cars at normal driving speeds, tyre/road interaction is a major source tothe exterior as well as interior vehicle noise. The interaction between a tyre and a roadsurface generates tyre structure vibrations, leading to sound radiation into the surroundingair, and to dynamic forces acting on the wheel hub. These forces are transmitted via thesuspension system to the car body, resulting in sound radiation into the passenger compartment.To reduce the exterior and interior noise produced by rolling tyres, a deep understandingis required of the physics involved in the excitation, transmission and radiationof tyre structure vibrations. The focus of this thesis is on modelling of the vibrationson a rolling tyre and their relation to the sound radiation and the forces acting on thewheel hub. To be specific, state-of-the-art simulation tools, involving a tyre model,tyre/road contact model and radiation model, are used to first identify the modes on a tyreresponsible for the radiation of sound during rolling. It was found that in the critical frequencyrange around 1000 Hz, where maximum radiation occurs, the radiation is mainlydue to low-order modes. These modes are not the ones with the strongest excitationaround 1 kHz, but have high enough radiation efficiency to dominate the sound radiation.The tyre model is then modified to incorporate the air-cavity and wheel, and used in connectionwith the contact model to simulate the forces acting on a blocked hub duringrolling. It was found that the transmission is strongly influenced by three modes: theradial semi-rigid body mode on the tyre, the first mode inside the fluid cavity and a wheelmode. Further, the spectra of the hub forces are concentrated to the low-frequency range(up to say 250 Hz). Finally, the thesis is also concerned with the extension of an existingcontact model for tyre/road interaction to encompass the tangential contact forces. Themodel is first validated towards an alternative contact formulation found in the literature.Thereafter, a minor parametric study is conducted to see the influence of rolling speed,road surface roughness and longitudinal slip ratio on the total radial and tangential contactforce

Investigation of stress-distribution in a car tyre with regards to rolling resistance

In recent years the method of waveguide finite element modelling has emerged as a suitable tool for the simulation of the structural behaviour of tyres. It combines cross-sectional finite element modelling with classical wave propagation methods along the waveguide. Compared to traditional finite element methods it is numerically much more efficient and provides greater physical insights into the vibrational behaviour. In an ongoing project an existing waveguide finite element model for the calculation of stationary (non-rolling) tyre vibrations is extended to allow for calculation of the stress distributions inside a rolling tyre being in contact with the ground. The results are used to identify local areas of high stress, which are not only important from a structural point of view but which can also be associated with high energy losses due to dissipation, hence affecting the overall rolling resistance of the tyre. The procedure and preliminary results will be presented

Waveguide-Finite-Element based parameter study of car tyre rolling losses

Low rolling resistance and a low noise level are two characteristics of a car tyre which are often seen as conflicting with each other. Simultaneously, there is an increased demand for improvement in both fields due to legislative changes. Due to the fact that there is little to no detailed information available on the relation between rolling resistance and acoustical behaviour of car tyres, an in-depth investigation of this subject seems to be desirable. In a first step, a Waveguide-Finite-Element-Model (WFEM) of a car tyre is combined with a non-linear 3D contact model to calculate the resulting contact forces between tyre and road surface. This can be used to make a detailed prediction of the tyre vibrations. For steady state rolling the input power into the tyre at the tyre-road interface gives the rolling resistance in terms of dissipated power. This includes detailed information on frequency and wave order distribution of dissipation. Using a parameter study, it is evaluated how the rolling resistance is affected by material properties or the tyre design

Waveguide-Finite-Element based parameter study of car tyre rolling losses

Low rolling resistance and a low noise level are two characteristics of a car tyre which are often seen as conflicting with each other. Simultaneously, there is an increased demand for improvement in both fields due to legislative changes. Due to the fact that there is little to no detailed information available on the relation between rolling resistance and acoustical behaviour of car tyres, an in-depth investigation of this subject seems to be desirable. In a first step, a Waveguide-Finite-Element-Model (WFEM) of a car tyre is combined with a non-linear 3D contact model to calculate the resulting contact forces between tyre and road surface. This can be used to make a detailed prediction of the tyre vibrations. For steady state rolling the input power into the tyre at the tyre-road interface gives the rolling resistance in terms of dissipated power. This includes detailed information on frequency and wave order distribution of dissipation. Using a parameter study, it is evaluated how the rolling resistance is affected by material properties or the tyre design