Through two complementary approaches, using modal response and wave propagation, the analyses presented here show the conditions under which a decaying impulse response, or a nearly irreversible energy trapping, takes place in a linear conservative continuous system. The results show that the basic foundation of near-irreversibility or apparent damping rests upon the presence of singularity points in the modal density of dynamic systems or, analogously, in the wave-stopping properties associated with these singularities. To illustrate the concept of apparent damping in detail, a simple undamped beam is modified to introduce a singularity point in its modal density distribution. Simulations show that a suitable application of a compressive axial force to an undamped beam placed on an elastic foundation attenuates its impulse response with time and develops the characteristics of a nearly irreversible energy trap.

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This presentation describes experiments that demonstrate the concept of energy sinks where a set of multiple undamped linear oscillators attached to a vibrating structure can absorb most of its energy. In principle, energy sinks do not require presence of damping in the classical sense. A set of undamped oscillators that make up an energy sink collectively absorb the vibratory energy and retain it in their phase space. Earlier optimization studies by the authors have shown the feasibility of vibration absorption and retention by energy sinks if the set of oscillators have a particular frequency distribution. Experimental results support the concept of energy sinks. Different physical realizations of energy sinks demonstrate the significance of frequency distributions and the ability of energy sinks to reduce vibration amplitude of a primary structure to which they are attached.

This paper presents experiments that demonstrate the concept of energy sinks, which when attached to a vibrating structure can absorb most of its energy. Energy sinks consist of a set of undamped linear oscillators and, in principle, do not require presence of damping in the classical sense. The set of undamped oscillators that make up an energy sink collectively absorb the vibratory energy and retain it in their phase space. Earlier optimization studies by the authors have shown the feasibility of vibration absorption and energy retention by energy sinks if the set of oscillators have a particular frequency distribution. Experimental results presented in this paper support the concept of energy sinks. Different physical realizations of energy sinks demonstrate the significance of frequency distributions and the ability of energy sinks to reduce vibration amplitude of a primary structure to which they are attached.

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