Experimental validation of elliptical contact tire model with friction coefficient deduced from viscoelasticity of tread rubber

This study proposes a mechanical tire model with deduced friction coefficient based on multiscale friction theory. In the proposed model, the contact shape and contact pressure distribution are calculated based on the elliptical contact tire model. In the calculation of longitudinal stress in the adhesion region, not only the longitudinal deformation in length direction owing to the slip ratio, but also the nonlinear deformation in width direction owing to the tread radius are considered. The coefficient of friction in the sliding region is deduced from the viscoelasticity of tread rubber by multiscale friction theory, with contributions from adhesion and hysteresis friction. The validity of theoretical calculation of coefficient of friction was verified by linear friction tests of a rubber piece conducted under two conditions: a dry road surface and a wet road surface with a water film mixed with detergent. It was confirmed that, with appropriate parameter settings, the longitudinal stress distribution in the tire contact plane calculated by the proposed method can reproduce the experimental results by inner drum tire tester better than the classical brush model. The proposed method can be applied to rubber compound design to achieve the desired braking and driving characteristics of tires because it analytically links the longitudinal forces of tire to the viscoelasticity of tread rubber.