Numerical Simulation of Digging Shovel Operation of Cassava Root

Abstract

Based on the methods including modified Mohr-Coulomb yield criterion, Lagrange and smoothed particle hydrodynamics (SPH), the digging shovel - stem - root - soil system dynamics simulation model is established by ANSYS/ LS-DYNA. According to the model, the interaction mechanisms among the digging shovel, soil and root are discovered, and the processes of soil shearing and the changing processes of root's stress are analyzed. The mechanisms of shovel's soil loosening are discovered. The process of soil deformation, fracture and loosening and the changing process of root's stress on micro level are studied. The results show that (1) the main reasons for soil loosening in the digging shovel operation are that the soil on the wedge is bended fracture due to being squeezed and uplifted, and that the soil is sheared and broken in the direction of the wedge's normal, and that the soil has no supporting of the blade so that a lot of fractures appear on the soil and is separated by the shovel blade, and that the upper and lower soil can't be closed; (2) when the wedge's extrusion attains a certain value, the links of root and soil will be destroyed; (3) the soil stress value around the wedge is largest, and the soil shearing rupture develops from bottom to top, and the shearing rupture surface occurs in the widest place of shovel blade in the direction of wedge's normal; (4) when the blade's tail points at the root, the root's effective stress is largest and makes the bending deformation of root forward and upward in the meantime, and when the root's effective stress is too large, the root will be broken and the harvest will be lost.