Implementation of non-linear contact stiffness and adhesion in a numerical model for tyre/road contact

Numerical tyre/road contact models that include the effects of adhesion are of interest both for fundamental understanding of the interaction and for optimisation of tyre/road combinations. A previously developed numerical time-domain contact model that includes the effect of small-scale roughness is here extended to investigate adhesive forces and inertial effects of the tread. Adhesion is modelled by allowing negative forces in the force-compression relations of each pair of matching contact elements. A limiting force for which the individual contacts break is tested as a preliminary separation criterion. Numerical instabilities were found in the dynamic calculations but measures were successfully implemented to increase stability. Calculation results indicates that tread inertia can be considered to have minor importance for small-scale tyre/road contact. Calculated time-force records of separation situations including the simple adhesion criterion are similar to experimental results in their character but lack dependence on contact history and unloading rate. The proposed model is able to simulate a tread block indenting and separating from a road surface, but the preliminary adhesion model was found to be insufficient and development suggestions are presented.