Effects of steering of tracked combine harvester on shear damage of paddy field soil

During steering, the slide and slip of the tracked combine harvester relative to the ground will cause serious shear damage to the soil and reduce the steering performance of the vehicle. The pivot steering mode of the combine harvester is gradually applied because of its significantly improved steering stability and efficiency compared to the traditional unilateral braking steering mode. However, the effects of the steering mode of the combine harvester on shear damage of soil remain unclear. In this study, a steering resisting torque model is established by considering the slide and slip condition of tracked vehicles. Meanwhile, the influence of slide and slip of the track on shear damage of soil is theoretically analyzed, and the steering tests of unilateral braking and pivot steering modes are conducted in the paddy field soil with different moisture contents using the tracked combine harvester. Besides, by testing the trajectory outline after steering, the soil shear area (disturbance area of the track) and shear deformation (the maximum elevated height and maximum shearing depth of soil) of soil are used as indicators to compare the shear damage to soil in the two steering modes. The results indicate that the slide and slip of the track coefficients are inversely proportional to the shear deformation of the soil, but they have no significant influence on the shear area of the soil. The combine harvester working in the pivot steering mode reduces the shear area of soil by about 50% compared with that of unilateral braking steering. When the track slip coefficient is smaller than the critical slip coefficient at this condition, the soil shear deformation caused by unilateral braking steering is larger than that of pivot steering. This research result provides some references for selecting the steering mode of the tracked combine harvester in different soil conditions.