Circumferential tire grooves form pipes in the contact patch and generate the nuisance noise, for which the fundamental natural frequency is approximately 1000 Hz for passenger car tires. The frequency coincides with the peak of pass-by noise spectrum. Therefore, controlling the groove resonance is of a main motivation of this paper to reduce environmental noise. If one lateral slot end is terminated in tread rib and if the other end merges to a circumferential groove, it is found that the slot performs as a side-branch or a Helmholtz subresonator to counteract to the pipe resonance. The slot parameters, such as cavity volume and the change in section area, determine the resonant frequency and effectively influence on the acoustic characteristics of whole groove space. Optimal slot geometry is widely investigated by using numerical analysis and validated by experiments. It is shown that the proposed tread design can significantly reduce groove noise without sacrificing other performances.
Rolling tire performance is frequently affected by multiple physics. For instance, dry handling is influenced by the tire temperature as a consequence of the heat generation by material viscosity and the heat transfer to ambient air. The general phenomenon is complex and even interactive in that the elasticity parameter affecting tire deformation is a function of the temperature and that the temperature depends considerably on the air flow on tire surface. This paper refers to connecting the different physics of outside air flow and thermomechanical system of tire. Especially, the heat transfer across tire surface is focused from the viewpoint of thermofluid dynamics. Macroscopic flow turbulence to accelerate the heat transfer is studied in a case study of the run-flat tire, where high temperature due to very large deformation is of a key issue. Numerical simulation is conducted in parallel to experimental works in assessing heat flow and temperature on the surface. It is shown that the proposed geometry of rib sidewall reduces the tire temperature and improves the tire life remarkably.
Vehicles, such as an agricultural tractor, construction vehicle, mobile machinery, and 4‐wheel drive vehicle, are often operated on unpaved ground. In many cases, the ground is deformable; therefore, the deformation should be taken into consideration in order to assess the off‐the‐road performance of a tire. Recent progress in computational mechanics enabled us to simulate the large scale coupling problem, in which the deformation of tire structure and of surrounding medium can be interactively considered. Using this technology, hydroplaning phenomena and tire traction on snow have been predicted. In this paper, the simulation methodology of tire/soil coupling problems is developed for pneumatic tires of arbitrary tread patterns. The Finite Element Method (FEM) and the Finite Volume Method (FVM) are used for structural and for soil‐flow analysis, respectively. The soil is modeled as an elastoplastic material with a specified yield criterion and a nonlinear elasticity. The material constants are referred to measurement data, so that the cone penetration resistance and the shear resistance are represented. Finally, the traction force of the tire in a cultivated field is predicted, and a good correlation with experiments is obtained.