Near-irreversibility in a conservative linear structure with singularity points in its modal density.

Department of Mechanics and Aeronautics, University of Rome, La Sapienza Via Eudossiana, 18, 00184, Rome, Italy.
The Journal of the Acoustical Society of America (Impact Factor: 1.65). 05/2006; 119(4):2141-9. DOI: 10.1121/1.2179747
Source: PubMed

ABSTRACT 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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