Mechanics of wheels on soft soils: A method of analyzing test results

Abstract : This report presents a method of analyzing the resuls of tests with pneumatic tires in sand. The method is based on considerng the work of the pull developed by the test wheel as the difference between energy input and energy dissipation. The parameters used to represent these energies are defined, and their meanings are described in some detail by referring to the theoretical case of a rigid wheel on a rigid surface. This theoretical case is also used as a reference system to evaluate the results of actual tests. Experimental data for a number of representative test conditions are presented and compared with the reference system. Concepts of efficiency are introduced and discussed. It is concluded that the proposed approach is promising for both conveniently expressing experimental results and understanding tire behavior in soft soils. However, more data will have to be analyzed to draw quantitative conclusions for practical use. Four appendixes are included in which certain aspects of the definitions of slip, stress distribution, lateral confinement of sand, and criteria for propelling-system efficiency are discussed.