TRACTOR TIRE ASPECT RATIO EFFECTS TRACTOR TIRE ASPECT RATIO EFFECTS ON SOIL STRESSES AND RUT DEPTHSON SOIL STRESSES AND RUT DEPTHS

摘要

A 580/70R38 tractor drive tire with an aspect ratio of 0.756 and a 650/75R32 tire with an aspect ratio of 0.804 were operated at two dynamic loads and two inflation pressures on a sandy loam and a clay loam with loose soil above a hardpan. Soil stresses were determined just above the hardpan beneath the centerlines and edges of the tires. Rut depths were measured at the centerline and edge of each tire track. The octahedral shear stress and rut depth were not significantly different for the tires. The peak octahedral normal stress was not significantly different for the two tires when the dynamic load was 17.2 kN, but was significantly greater for the 650/75R32 tire when the dynamic load was 30.9 kN. Soil stresses and rut depths increased with increasing dynamic load at constant inflation pressure, and with increasing inflation pressure at constant dynamic load. Net traction and tractive efficiency decreased with increasing inflation pressure at constant dynamic load. At constant inflation pressure, tractive efficiency increased with increasing dynamic load. In comparisons of the centerline and edge locations, soil stresses were significantly less beneath the edges than the centerlines of the tires. Ratios of the mean stress beneath the centerline to the mean beneath the edge for four combinations of dynamic load and inflation pressure ranged from 2.18 to 3.77 for the peak octahedral normal stress and 1.76 to 3.18 for the corresponding octahedral shear stress. Ratios of the rut depth at the centerline to the edge ranged from 1.04 to 1.49. In summary, for these two tires with their slightly different aspect ratios, no fundamental differences were found that would clearly indicate that one tire was better than the other.