Methods of calculating the resistance and the moment of resistance to cutting the soil with a straight blade knife cutters

Abstract

During the process of cutting the soil, the blade knives of the cutter and its hub experience cyclic loads. Therefore, along with the calculation of the knives for static strength, their calculation for fatigue strength is necessary. To carry out such a calculation, it is necessary to know the dependence of the main vector of the soil resistance forces to cutting and the main moment of these forces on the angle of rotation of the cutter. The construction of the methodology for calculating the resistance and the moment of resistance to cutting the soil with a plate knife, depending on the angle of rotation of the cutter, is the purpose of this study. Based on the proposed mathematical model of the interaction of the knife blade with the soil, such a calculation method has been developed. The obtained analytical dependences also include the geometric and operational parameters of the cutter. The relative depth of the cutter and its kinematic parameter, which is equal to the ratio of the peripheral speed of the end of the knife to the speed of the translational movement of the cutter, are taken as regime dimensionless parameters. It was shown that the resultant reaction of the soil to the knife blade during cutting periodically changes its value, direction and application point, and the maximum values of the driving force, the modulus of the resultant forces of soil reactions and the modulus of the total moment of soil resistance to cutting monotonously increase with an increase in the relative depth of the cutter. The angle, which is the resultant of the forces of soil reactions with the direction of movement of the cutter, decreases almost linearly with an increase in the angle of rotation. The technique allows to significantly simplify experiments to determine the power characteristics of the cutter and significantly reduce their volume, since it requires the determination of only one empirical constant. Due to the generality of the basic starting points, the proposed methodology can be mainly transferred to other rotational working bodies. Laboratory experiments conducted in the soil channel confirmed the adequacy of the proposed mathematical model for the interaction of the cutter blade with the soil.