A study of soil-tire interactions using finite element method

Traction that can be developed by a tire is a result of the interaction between tire and soil. Tires are complex with respect to the incompressibility of rubber and the anisotropic properties of cord-rubber laminates. The complicated geometrical shape of a tire and the distribution of the loads on the tire have been limiting factors for traction and related studies. Nevertheless, considerable progress has been made to understand tire behavior in studies focused on tire-rigid surface interactions. In this study the soil-tire interface pressures were measured and it was found that tires, their size and construction related variables and initial soil conditions are responsible for interface pressures. There was a high correlation between the tire variables and interface pressures. The highest interface pressures from the statistical analysis was found to be at the edge of the tire and the finite element method verified this information. Studies in the past assumed a uniform pressure distribution under a tractor tire. However this is not the case when tires carry a high axle load. Due to the complex nature of the soils, the soil-tire interaction has usually been studied experimentally. The traction models created in the past were usually based on the results of cone measurements that were hard to correlate with soil conditions. A methodology to study soil-tire interaction was developed in this study and a Finite Element Method based study was conducted. The results were used to develop a traction model that uses a dimensionless number called the Rigidity Index which represents the dynamic behavior of the soil under load. In the compact form, the rigidity index includes the necessary soil and tire variables.