Development and study of mathematical model of pneumatic vehicle of a lower pressure and soil interaction

This study examines the interaction of pneumatic vehicles of a lower pressure of forestry machines with soil surfaces with reduced bearing capacity. Mathematical modeling and numerical methods were used to implement the developed mathematical model, and a computational experiment was conducted. The study showed that for pneumatic vehicles of a lower pressure on Category III forest soils (“classic” weak forest soils), as well as on more concrete surfaces, the tire bearing capacity is the limiting factor for the vehicle weight. For a standard-size tractor wheel, the bearing capacity weight limitation is observed for soil conditions close to Category II (medium-strength forest soils) or higher. Processing the calculated data revealed a linear function for the tractor's traction and thrust properties at a weight limited by a rut depth of 0.2 m or, for more durable soil surfaces, by the tire's bearing capacity. It was established that, while adhering to the rut depth and bearing capacity limitations, the tractor possesses drawbar-pull coefficient estimate that is a quadratic function of the soil deformation modulus. This is advantageous from a technological perspective, as the presence of isolated obstacles is likely along the vehicle's path. Formulae for calculating the rolling resistance coefficient, net thrust coefficient, and drawbar-pull coefficient for the specified tractor weight limitations are presented for practical purposes. Comparison of the results of the computational experiment implementing the model for standard forestry tires and low-pressure pneumatic tires showed that, with an acceptable vehicle weight, the drawbar-pull of the pneumatic vehicle on the soil is comparable to that of a standard one, while the rolling resistance coefficient decreases by an average of 39%, and the drawbar-pull coefficient increases by an average of 43%.

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