DOI: 10.18245/ijaet.2015038 ISSN: 2146-9067

On the kinematic model approximation of granular dampers under vertical vibration

Furkan Terzioglu
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Granular dampers are utilised to control vibration in a wide range of industries, including automotive, aerospace, machine tool and civil engineering applications, where their robustness, tolerance of harsh environments and freedom from maintenance make them attractive where conventional damping treatments cannot be used. The energy dissipation of a granular damper is governed by the collective motion of the particles, which is normally predicted using discrete element simulations that are computationally demanding. This paper examines how far this collective motion can be described by a simple kinematic model in which the granular medium is treated as a single rigid body that detaches from the enclosure, travels freely under gravity, and collides inelastically with the enclosure ends. Conditions are obtained for the detachment and re-contact instants and for the excitation amplitudes at which the collective collisions are most effective. The predictions are compared with previously reported discrete element simulations and measurements of the dissipated power of a cylindrical damper excited at different frequencies. The model reproduces the simulated collective velocity histories and locates both optimum amplitudes with acceptable accuracy. The simple models fail in the intermediate amplitude range, where the collective motion extends over several excitation periods, and at high frequencies, where the compliance of the medium becomes important. Within these limits, the model can support the early sizing of dampers for practical applications at a small fraction of the computational cost of the simulations.

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