We present a dynamic simulation of a wire rope involving both contacts with a winch drum and hydraulic systems using the finite element method. Rapid winch operation often causes disorderly winding of the wire rope, which is an important quality problem. Dynamic simulation is, therefore, required for design of the hydraulic winch system on construction machinery. The wire rope is modeled using by truss elements considering large displacement motion. The contact between the wire rope and the winch drum is modeled using by variable-length truss elements and bilinear spring elements. An improved Newton method is proposed for nonlinear dynamic analysis. Simulation results show that some lever operations result in rope looseness and intense pressure fluctuation.
The acoustoelastic effect in rolled metals is examined experimentally by the ultrasonic method. The first experiment is concerned with the birefringence due only to the texture-induced anisotropy. In the second experiment, the uni-axial tensile stress is applied to five specimens which are differently inclined from the common rolling direction, and the birefringence due to both the slight orthotropy and stress is examined. Though the experimental results are a little complicated, they are well explained by those theoretical acoustoelastic relations which one of the authors previously proposed for slightly orthotropic materials. This means that, in general, the polarization directions are fairly rotated by the stress, which is explicitly reaffirmed by the third experiment. It is the main conclusion of the present paper that the acoustoelastic relations referred to above are essential for rolled metals. In previous experimental works, slight anisotropies of polycrystalline metals were hardly taken into account, and hence the stress-induced rotation of the polarization directions could not be treated quantitatively.
Recently, HILS(Hardware in the Loop Simulation) has been investigated in the field of the multibody dynamics(MBD). The fast calculation is necessary for the HILS system in order to require the real time simulation. This paper presents a fast simulation technique using the domain decomposition method. The domain decomposition method is widely used in the dynamic simulation for the mechanical system involving the hydraulic control system. This method is, however, not absolutely stable as the numerical integration. Fujikawa proposed a numerical stable solution scheme by introducing the iteration calculation. This paper applies the method to actual simulations of flexible multibody system in which the flexible linkage system and the hydraulic drive system are coupled with each other, and examines the speedup by parallel computing with the common memory in the calculation time. It is shown that using the present method in a multi-degrees-of freedom model can shorten the computing time. The present method is effective for the speedup in the calculation time by applying the dynamic simulation of the actual digging works on the hydraulic excavator.
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