Tire–Deformable Terrain Interaction Model for Longitudinal Slip Based on Contact Characteristics

Unlike the contact between tires and paved road, the tire–deformable terrain interaction is more complex, often involving traction, compaction resistance, slip sinkage, and other factors. This study introduces a novel “constant-sinkage” finite element analysis framework to decouple the effects of slip and sinkage and obtain clearer tire–terrain contact mechanisms. High-fidelity simulations of rigid and flexible tires under longitudinal slip reveal a key insight: the contact contour remains largely invariant with slip when sinkage is fixed and is only affected by the relative strength of the tire and the terrain. This discovery enables the systematic investigation of stress distribution, characterized by three distinct stages corresponding to increasing slip. Based on these findings, a new stress distribution model applicable across all slip stages is developed, incorporating soil parameters obtained from penetration and shear tests. This stress model is integrated with an improved contact contour model based on a surrogate circle, forming the basis of the accurate prediction of tire forces such as drawbar pull. Validation confirms that the model can effectively represent the in-plane characteristics of tires on deformable terrain and provide a robust foundation for off-road vehicle simulation.