Force prediction models for brittle and flow failure of soil by draught tillage tools

Abstract

Models have been developed to predict the forces acting on tillage tools of simple shape. The models are a useful advance on previous prediction models because they take account of the different types of soil disturbance or failure that may be caused by a tillage tool. The effect of tool speed on forces, which can be very significant, is taken into account. It is shown that, in brittle failure, the effect of speed is due to inertial forces and rate effects on soil-metal friction. With flow failure, inertial effects are negligible and the large effect of strain rate on soil shear strength dominates. The models have been verified with force data from soil tank experiments.