Calculation of normal stiffness and contact patch of ultra-low pressure tires for agricultural machinery

Abstract

BACKGROUND:The impact of tires on a deformable ground surface determines not only the ability of a vehicle to move, but also the pressure on ground through the contact patch geometric characteristics. The pressure on soil is normalized and limited by the conditions for the preservation of its agrophysical properties. Therefore, when creating vehicles for various purposes for their movement or movement of their trailers on deformable ground surfaces, it is required to calculate the pressure on ground in the design process. However, currently there are no universal dependencies for calculation of the mentioned parameters of ultra-low pressure tires. This applies to both vertical and inclined tire arrangement. AIMS:Development and implementation of universal methods for calculation of normal stiffness and con-tact patch parameters of ultra-low-pressure tires for agricultural machinery. MATERIALS AND METHODS:Software products such as MS Excel, MATLAB and Curve Expert Professional were used in modeling. RESULTS:The universal analytical-experimental dependence has been obtained to determine the normal stiff-ness of ultra-low pressure tires, including a possible inclination of the wheel rotation axis. The dependence takes into account tire pressure, normal wheel load, an inclination angle of the rotation axis and tire geometric characteristics. The formula is obtained for determining the contact patch contour area of an ultra-low pressure tire. It helps to calculate the current pressure on ground, which should not exceed the specified value. CONCLUSIONS:The method for calculation of normal stiffness and contact patch parameters such as contact length, contour area and contact pressure for ultra-low pressure tires has been developed and implemented. The method is universal for all ultra-low pressure tires.