The Tire Society was established to disseminate knowledge and to stimulate development in the science and technology of tires. These ends are pursued through seminars, technical meetings and publication of the journal, Tire Science and Technology. The Society is a not-for-profit Ohio corporation that is managed by a duly elected Executive Board of Tire Industry professionals who serve on a volunteer basis.

Today's tread pattern design development is done independently from the tire body construction in order to achieve the best traction and uniform local wear performance. Nevertheless, a better understanding of the interaction between tread and body is necessary to improve the above mentioned properties. An identical tire has been investigated in four pattern steps, starting from a smooth tire, carving a block structure with longitudinal and lateral grooves, and finishing with additional sipes in the blocks. A new developed test stand, which is capable of measuring the stresses in the contact patch of the rolling tire in all directions with a resolution of 1 mm, is described. The local contact stresses of the investigated tread blocks are simulated by FEA using the measured loading conditions of the smooth tire. The results of this simulation are compared with measurements and mechanically interpreted.

The presented investigation is motivated by the need for performance improvement in winter tires, based on the idea of innovative “functional” surfaces. Current tread design features focus on macroscopic length scales. The potential of microscopic surface effects for friction on wintery roads has not been considered extensively yet. We limit our considerations to length scales for which rubber is rough, in contrast to a perfectly smooth ice surface. Therefore we assume that the only source of frictional forces is the viscosity of a sheared intermediate thin liquid layer of melted ice. Rubber hysteresis and adhesion effects are considered to be negligible. The height of the liquid layer is driven by an equilibrium between the heat built up by viscous friction, energy consumption for phase transition between ice and water, and heat flow into the cold underlying ice. In addition, the microscopic “squeeze-out” phenomena of melted water resulting from rubber asperities are also taken into consideration. The size and microscopic real contact area of these asperities are derived from roughness parameters of the free rubber surface using Greenwood-Williamson contact theory and compared with the measured real contact area. The derived one-dimensional differential equation for the height of an averaged liquid layer is solved for stationary sliding by a piecewise analytical approximation. The frictional shear forces are deduced and integrated over the whole macroscopic contact area to result in a global coefficient of friction. The boundary condition at the leading edge of the contact area is prescribed by the height of a “quasi-liquid layer,” which already exists on the “free” ice surface. It turns out that this approach meets the measured coefficient of friction in the laboratory. More precisely, the calculated dependencies of the friction coefficient on ice temperature, sliding speed, and contact pressure are confirmed by measurements of a simple rubber block sample on artificial ice in the laboratory.

Due to shorter development cycles and high cost pressure, the tread pattern development process is optimized by an analysis tool, which can predict the influence of the tread pattern on several tire properties. By using this tool conventional development cycles can be substituted by several virtual development cycles. The tool modules for the tire properties traction, handling, plysteer residual aligning torque (PRAT), groove wander, and noise are presented in this paper. The applicability of evolution strategy on tread pattern development is demonstrated, being another prerequisite for a future virtual pattern development process.

Evaluation of tread pattern designs with respect to performance of winter tires on snow is still predominantly based on empirical knowledge. To gain greater insight into the complex interaction between the elastic tread block and the inelastically deforming snow, numerical simulations by means of the Finite Element Method (FEM) were carried out in conjunction with experimental investigations. An elastoplastic material model for snow was developed. Calibration of the model parameters is based on shear and compression tests conducted on specimens made of natural and artificial snow. Good correlation is obtained between results from laboratory experiments and from numerical simulations with respect to the deformations and the frictional behavior of a single rubber block sliding on snow.