SAE International Longitudinal Interfacial Forces of the Interaction of a Treaded Tire with Snow 2008-01-1415

Although it is intuitively and qualitatively known that a treaded tire has a larger drawbar pull than a smooth tire, little is known quantitatively about all the interfacial forces and the origins of these forces of a treaded tire traversing a snow cover. There have been relatively few studies regarding the quantitative effects of tread pattern on tire-snow interaction due to the complexity of the tread pattern, the enormous amount of computational resources needed for high-fidelity numerical simulations, and the difficulty of measuring all the interfacial forces between a tire that is much harder than snow. The purpose of this paper is to understand the effects of a simplified tread pattern of a two-dimensional rigid tire on the interfacial forces between a tire and low-density snow. The parameters to vary included the wheel load, as well as a full-range of longitudinal slip. Snow sinkage, snow density, traction, motion resistance and drawbar pull were obtained as a function of input parameters and parts of the tire; the results were compared with those of a smooth tire. It was found that a larger shear force on the void at higher slip ratios contributes significantly to the increase of traction of a treaded tire. The treaded tire has a larger drawbar pull than the smooth tire at higher slip ratios due to a larger decrease in motion resistance relative to traction. It was also shown that the positive normal contact force on the flank increases with slip ratio, as a result of the larger torque, and is the dominant cause of the decrease of the motion resistance at higher slip ratios leading to a higher and desirable drawbar pull.