Interfacial Forces Between Tire and Snow Under Different Snow Depths

All the frictional forces developed from tire-snow interfaces are closely associated with snow depth and snow sinkage. One of the important differences between tire-soil interaction and tire-snow interaction is that the latter is explicitly snow depth dependent. Based on our established depth-dependent upper bound indentation model, the effects of snow depth on tire-snow interaction are presented in this paper. Snow is considered as a pressure-sensitive Drucker-Prager material. The required snow material parameters of the model are Drucker-Prager material constants only. Snow sinkages, for longitudinal slip close to zero, under different snow depths are numerically solved through the sinkage solver. The comparison between sinkage obtained analytically and the sinkage computed from finite element simulation is very good. Motion resistance, tractive effort (shear force) and drawbar pull (net traction) are analytically calculated and agree reasonably well with finite element simulation data. The effects of slip angle on snow sinkage are not significant. This means that longitudinal shear force at zero longitudinal slip is insensitive to slip angle. The results also show that lateral shear force has a non-monotonic relationship with snow depth although it increases monotonically as slip angle increases. The depth-dependent analytical tire-snow modeling methodology can be further applied to vehicle mobility and performance analysis in cold regions.