Off-road cars and tractors with 3D tyre models for fast rolling simulation

摘要

External tyre dynamics means the rolling of a membrane-type elastic body with a small bending disturbance. Internal tyre dynamics is the coupling between belt and carcass by rubber shear forces and between belt cord layers by the shear of rubber coatings. One has to take into account that cord stresses in the belt in reality are smaller than they are prescribed by the membrane kinematic. The first approximation is to reduce the belt cord stiffness at belt shoulders near the sidewalls. A further approach is to introduce more degrees of freedom for describing the shear deformation in a separate computer program. To avoid extensive computations, a 2D tyre model for rolling on road and in soil was used for cars and tractors. In the case of a 2D tyre model, the longitudinal stiffness of the belt (a mean value) can be computed by using the measured expansion of tyre during the inflating process. Out of the plane, the body behaves as a rigid ring on elastic foundation. Within the sidewalls, the cords are radially orientated; the rubber is only a coating. This model is much faster in computation and can also be used for crash simulation and for tyre noise computing. To compare rolling on deformable soil with rolling on road, a 3D tyre model was used. Several examples, also landing of an airplane on a grass field, are given.