PREDICTING SOIL-RIGID WHEEL PERFORMANCE USING DISTINCT ELEMENT METHODS

摘要

A two-dimensional discrete element model (DEM) for the interaction between a rigid wheel and soil is presented using PFC2D code. The soil particles are modeled by clumps of two discs. The contact model between the particles includes cohesion by a so-called softening model. The parameters of the model represent soil having a cone index (CI) of 200 kPa or 400 kPa. The model of the wheel is based on 30 grousers, spaced equally around a drum 200 mm in diameter and 100 mm in width. Dynamic simulations were performed with different combinations of drawbar force, vertical load, and soil conditions. The traction performance of the wheel was calculated, and the results were compared with known theories and reported test results. The simulation results show reasonably good correlation, quantitatively and qualitatively, with previously reported results and theories, and emphasize the ability of the DEM to simulate soil-wheel interaction for design purposes. Prediction of wheel performance as a function of slip for driven, self-propelled, and towed wheels is presented for different combinations of soil conditions and vertical loads. The ability to investigate soil deformation, stress distribution beneath the wheel, and the influence of slip on sinkage is shown. Contrary to the prediction of empirical theories, the simulations suggest that vertical load and soil CI have different influences on tractive performance; this point warrants further investigation. The model also predicts a different behavior of motion resistance and net traction at high slip rates compared with empirical and semi-empirical methods.