Experimental Validation of Elliptical Contact Patch Tire Model

The influence of tires on vehicle dynamics, as the only automotive component in contact with the road surface, is significant. Mechanical models such as the Fiala model includes tire mechanical properties as parameters and are useful for tire design studies. These models assume a rectangular or trapezoidal tire contact shape, which does not always match the tire contact shape observed when slip angle is applied, leaving room for improvement in accuracy. This study proposes a new semiphysical tire model with an elliptical contact shape, termed the “elliptical contact model.” First, the expressions for the contact shape and contact pressure distributions in the elliptical contact model are formulated. Herein, we consider both the length- and width-direction distributions of the contact pressure in these expressions. Second, the formulation of the lateral shear stress distribution in the contact patch is presented based on the Fiala model, including the belt bending deformation by a lateral force and switching between the lateral shear and dynamic frictional forces. Lateral stresses proportional to the width coordinate are also introduced, enabling the calculation of lateral stresses acting in a direction counteracting each other at the widthwise edge of the tire contact surface. The model is validated by measuring a slick tire at a velocity of 100 km/h with slip angles of 0° and 3° using an Inside Drum Machine with an aluminum road segment with quartz piezoelectric sensors. Consequently, by setting appropriate model parameters, the contact pressure and lateral shear stress distribution results calculated using the model are consistent with experimental results. The accuracy of the proposed model could be further improved by revising the method of setting the static and dynamic friction coefficients.