Numerical investigations of traction behaviors of a pneumatic tire on wet granular terrains: DE/FE simulations

This paper presents a discrete element/finite element (DE/FE) coupling method to investigate the trafficability of off-road tires on wet granular terrains. Firstly, a DE model of the wet terrain is established, and a linear contact model is adopted to describe the interaction between particles, while the adhesion effect between wet particles is simulated by a liquid bridge force model. An FE model of an off-road tire is then developed, and the Yeoh hyperelastic material model is used to describe the large deformations and nonlinear mechanical behaviors of the off-road tire. Furthermore, numerical simulations of the angle of repose of wet particles are compared with experimental studies to verify the effectiveness of the DE/FE coupling method. Finally, the tire traction behavior under different complex working conditions is predicted by the presented DE/FE coupling approach. The simulation results show that the absolute value of tire sinkage increases almost linearly (the sinkage is 97.1 mm at 25% moisture content) with the rise of moisture content among particles. The rate of change of sinkage is greater for small friction coefficients ($<$ 0.3) than that for large friction coefficients ($⩾$0.3). The drawbar pull experiences a rapid increase for the slide friction coefficient with a range 0.3 and 0.7, after which the rate of change slows down ($⩾$0.7). However, the drawbar pull exhibits an opposite trend as the tire pressure and height of the tread pattern increase. Numerical results also indicate that the smaller the slide friction coefficient, the larger the soil deformation, flow, and failure area in wet granular terrains.