Abstrakt

In the paper, vibrations of a hybrid multibody-continuous system are investigated. For all the mechanical devices, effective damping methods are crucial in the design process. To obtain it, installation of viscous dampers or elasto-viscous elements is dominant. In the paper, an alternative method is investigated. It is based on modal disparity. To describe the method briefly, when structural damping is present in continuous systems, high frequency vibrations are better damped in general. To accelerate the low frequency damping, energy transfer between different modes can be helpful. Such transfer is impossible when linear systems are considered. It becomes possible, when nonlinear elements are present, e.g., when a mechanical system is introduced and it is set in its pose closed to its kinematical singular position. To test the hypothesis, a numerical model is proposed and tested. The mechanism is modelled as a multibody system composed of two rigid bodies. Joint displacements are considered as system generalized coordinates. The Newton/Euler’s equations are developed for free body diagrams, and then they are combined with the kinematics equations and projected on joint axes. To express dynamics of the continuous beam, finite elements are used. Deformations of a set of selected points (nodes) are considered as the coordinates. To joint the subsystems, constraint equations are introduced. Next, the Lagrange’s multipliers and the dependent coordinates are eliminated. Efficiency of free vibrations damping was verified in some earlier. Presently reaction of the system is tested for the forced vibrations, only. Unfortunately, in the presently considered case, the proposed system is less effective. Some reduction of the amplitude is observed for the forced vibrations. Range of the reduction is low. This damping method should not be recommended in case of forced vibrations. For the final recommendations, some additional investigations should be recommended to obtain better description of the phenomena present there.

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