A hydraulic excavator is taken as the object to study. Considering the characteristics of slewing transmission mechanism of hydraulic excavator, the torsional vibration equation is established by the finite element method. According to the torsional vibration equation, the effects of the equivalent moment of inertia of working device on the torsional dynamic properties of slewing transmission mechanism are analyzed. Using the optimization theory, the mathematical model is built, which is by means of the equivalent moment of inertia of working device as objective function and by means of the position parameters of the working device as design variables. Based on the mathematical model, the optimization of torsional dynamic properties of slewing transmission mechanism is studied. Finally, a numerical example is presented.

Based on the methods including modified Mohr-Coulomb yield criterion, Lagrange and smoothed particle hydrodynamics (SPH), the cassava stem - root - soil system dynamics simulation model is established by ANSYS/ LS-DYNA. The interaction mechanisms between uprooted cassava root and soil are discovered. The processes of soil shearing and the changing processes of root's stress are analyzed. The studies show that (1) the effects of root being extruded on the soil expand gradually from inside to outside in the process of uprooting, and the uprooted force reaches the maximum value when the soil appears ring shear rupture; (2) after the uprooted force reaches the maximum value, the root's effective stress still increases gradually with the increasing of its bending deformation until the soil is separated,and root's maximum effective stress appears in the combination of the root and stem where is the most easily to be broken;(3)when the maximum uprooted force on cassava root is analyzed, the interaction of a disc and its extension on the soil is regarded as the mechanical model of maximum uprooted force on cassava root.

A lateral-torsional coupled vibration model of the slewing mechanism of a hydraulic excavator is developed with consideration of the effect of lateral vibration and torsional vibration of sun gear and planetary gear on mesh displacement, the mesh stiffness of gear pairs, the bearing stiffness of the planetary and the coupling relationship of two stage planetary gear trains. The dynamic response of the slewing mechanism of a hydraulic excavator is obtained. Compared to the pure torsional vibration, the lateral-torsional vibration model is more reasonable.

Taking the generator and turbine as an integrated system, the nonlinear coupling dynamic equations of the system are established by the finite element method. According to the dynamic equations, the global coupling relations among the structural parameters, fluid parameters and electromagnetic parameters are discovered. Based on the dynamic equations, the dynamic responses of the system are calculated and analyzed. The results show that not only the structural parameters, but also the fluid parameters and the electromagnetic parameters have significant effects on the dynamic responses of the system. Finally, an example is presented.

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.