A theoretical study of the limit path of the movement of a layer of soil along the plough mouldboard

•Motion of a soil layer along mouldboards and dynamic component of draught resistance.•Dynamic component of plough draught resistance and "wrapping angle of layer" factor.•Mouldboard design and arrival angle of soil layer onto ploughshare affect resistance.•The proposed approach considers only the geometry of the surface of mouldboards. There have been studied regularities affecting the magnitude of the dynamic component of the plough resistance for cylindrical mouldboards, and its peculiarities for cylindroid mouldboards depending on the direction of arrival of the soil layer on the ploughshare. The dynamic component of the draught resistance of the plough, which is directly proportional to the square of the ploughing velocity, can be estimated by the value of a dimensionless coefficient, conditionally named the "wrapping angle of the layer". This coefficient can be found for the mouldboard surface if the path of the movement of the mid-point of the section of the soil layer is known. By example of a cylindroid surface of the mouldboard it is shown how the dynamic component of the resistance varies depending on the design parameters of the mouldboard and the direction of arrival of the soil layer onto the ploughshare. As a result of the experimental study, a reduction of the longitudinal component of the thrust on the plough body, equipped with a mouldboard with an improved design made according to the results of the theoretical study, was achieved. This reduction was obtained by reducing the friction force due to the dynamic component of the resistance forces.