Steerability analysis of multiaxle wheeled vehicles. Report 1, Development of a soil-wheel interaction model

This report describes the development of a mathematical model for calculating the motion resistance, sinkage, drawbar pull, torque, and side force for a flexible wheel traversing a yielding (or deformable) surface. To facilitate computations, the deformed boundary of the wheel is assumed to be an arc of a larger circular wheel. The entire soil-wheel interaction process is treated as two springs in series, one describing the flexibility of the tire and one describing the elastic-plastic deformation of the soil. Mathematical expressions are derived for the two spring constants in terms of the load deflection characteristics of the tire, the undeflected configuration of the wheel, and the mechanical properties of soil (both shearing response and compressiblity characteristics). The system of equations describing the performance of the wheel is solved numerically via a computer program called TIRE. An extensive series of parametric calculations is conducted with TIRE to demonstrate the application of the methodology and to study the performance of flexible wheels on different types of soil under various kinematic conditions. A partial validation of the proposed interaction model is established by comparing the results of laboratory tests for clay, sand, and mixed soils with corresponding model predictions. (Author)