Open AccessOperating characteristics of modern multi-axle off-road vehicles allow them to overcome successfully various engineering structures such as ditches, trenches, embankments, etc. A theoretical study of the transmission loading process under these conditions requires knowledge of characteristics of all power train elements, including those of the tire when it contacts the plane and large bump.
The paper presents research results of wide-section tire characteristics of the model I-247 (1200x500-508) on the long length bumps under static loading by radial force and torque at the internal air pressure in the tire of 0.35, 0.20, and 0.05 MPa. The research has been conducted on a special stand. As the bumps, were used two triangular prisms with the rounding vertex angles of 120 ° and 90 ° having radius of 100 mm. The threshold bumps were used as well. Their sizes were selected so that in all measuring options a tire was in contact with bump.
The nature of tires load behavior on the bumps with radial and angular deformation and in contact with the plane, essentially, does not differ. With such shapes and sizes of bumps a contact surface appearance has less impact on the tire torsion stiffness than on the radial one. Thus, at a nominal internal tire pressure of 0.35 MPa, a torsion stiffness of the tire is decreased, in average, by 5%, while the radial one is reduced by 25% when there is a transition from the contact on the plane to the contact with bumps.
It should be noted that at the transition from the plane contact to the that of with bumps the limit values of the tire radial stiffness ratio are significantly reduced, namely: up to 50% at internal tire pressure of 0.20 and 0.35 MPa, and up to 71% at internal tire pressure of 0.05 MPa.
The results of experimental research enable the following mathematical modeling: full approximation of tire load characteristics in case of instability of its smoothing a single bump; maximum loads and calculation of load modes of units and systems when a vehicle overcomes engineering structures and large bumps, taking into account the nonlinear features of tire behavior in its radial and torsion deformation.