Browsing by Author "Roveri, N."

Now showing 1 - 4 of 4

Open Access
Energy equipartition and frequency distribution in complex attachments
(Acoustical Society of America, 2009) Roveri, N.; Carcaterra, A.; Akay, A.
As reported in several recent publications, an undamped simple oscillator with a complex attachment that consists of a set of undamped parallel resonators can exhibit unusual energy sharing properties. The conservative set of oscillators of the attachment can absorb nearly all the impulsive energy applied to the primary oscillator to which it is connected. The key factor in the ability of the attachment to absorb energy with near irreversibility correlates with the natural frequency distribution of the resonators within it. The reported results also show that a family of optimal frequency distributions can be determined on the basis of a variational approach, minimizing a certain functional related to the system response. The present paper establishes a link between these optimal frequency distributions and the energy equipartition principle: optimal frequency distributions are those that spread the injected energy as uniformly as possible over the degrees of freedom or over the modes of the system. Theoretical as well as numerical results presented support this point of view. © 2009 Acoustical Society of America.
Open Access
Frequency intermittency and energy pumping by linear attachments
(Elsevier, 2014-09-01) Roveri, N.; Carcaterra, A.; Akay, A.
The present paper considers the problem of realizing an effective targeted energy pumping from a linear oscillator to a set of ungrounded linear resonators attached to it. Theoretical as well as numerical results demonstrate the efficacy of using a complex attachment as a passive absorber of broadband energy injected into the primary structure. The paper unveils also the existence of an instantaneous frequency associated with the master response characterized by intermittency: a rather surprising result for a linear autonomous system. Comparison with nonlinear energy sinks demonstrates that the two systems have some analogies in this respect and that the linear complex attachment is a very efficient energy trap. (C) 2014 Elsevier Ltd. All rights reserved.
Open Access
Targeted energy pumping using a linear complex attachment
(ISMA, 2012-09) Roveri, N.; Carcaterra, A.; Akay, Adnan
The present paper considers the problem of realizing an effective targeted energy pumping from a linear oscillator to a plurality of ungrounded linear resonators, attached to it in parallel. Theoretical as well as numerical results demonstrate the efficacy of using a complex attachment as a passive absorber of broadband energy, injected into the primary structure. The paper unveils also the existence of an instantaneous frequency associated to the master response characterized by intermittency: a rather surprising result for a linear autonomous system. A comparative analysis with a nonlinear energy sink demonstrates that the two systems present some analogies in this respect and that the complex attachment is a very efficient energy trap.
Open Access
Vibration absorption using non-dissipative complex attachments with impacts and parametric stiffness
(Acoustical Society of America, 2009) Roveri, N.; Carcaterra, A.; Akay, A.
Studies on prototypical systems that consist of a set of complex attachments, coupled to a primary structure characterized by a single degree of freedom system, have shown that vibratory energy can be transported away from the primary through use of complex undamped resonators. Properties and use of these subsystems as by energy absorbers have also been proposed, particularly using attachments that consist of a large set of resonators. These ideas have been originally developed for linear systems and they provided insight into energy sharing phenomenon in large structures like ships, airplanes, and cars, where interior substructures interact with a master structure, e.g., the hull, the fuselage, or the car body. This paper examines the effects of nonlinearities that develop in the attachments, making them even more complex. Specifically, two different nonlinearities are considered: (1) Those generated by impacts that develop among the attached resonators, and (2) parametric effects produced by time-varying stiffness of the resonators. Both the impacts and the parametric effects improve the results obtained using linear oscillators in terms of inhibiting transported energy from returning to the primary structure. The results are indeed comparable with those obtained using linear oscillators but with special frequency distributions, as in the findings of some recent papers by the same authors. Numerically obtained results show how energy is confined among the attached oscillators. © 2009 Acoustical Society of America.