Browsing by Author "Akay, Adnan"

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Open Access
Damping mechanisms
(Springer, Vienna, 2014) Akay, Adnan; Carcaterra, A.; Hagedorn, P.; Spelsberg-Korspeter, G.
The term damping is used to describe the means by which oscillation amplitudes are reduced through irreversible removal of vibratory energy in a mechanical system or a component. Dissipation, on the other hand, refers to the mechanism by which irreversible energy transfer, from vibratory to thermal, takes place. In this sense, damping is a macro-scale manifestation of atomic-scale dissipation. High damping is desirable to attain low vibration and noise levels whereas low damping is desirable for increased sensitivity in sensors and certain precision instrumentation. Damping is most obvious at resonance where the stiffness and inertia forces become equal. As a result, damping is a key factor in predicting vibration response of structures. As we will see in the following sections, there are numerous paths to damping and in a complex structure several means of damping may take place simultaneously at different locations throughout the structure. Accordingly, in determining the response of a vibrating structure, the total effect of all types of damping that may be distributed throughout a structure must be taken into account. Measurements of damping normally indicate the total damping a system experiences. It is difficult to isolate a component or a subsystem or a material within a system and measure its damping. In describing the various damping mechanisms, we will examine each through its effect on a single-degree-of-freedom (sdof) oscillator. In this section, we will review the response of a simple oscillator and examine the role of damping on it and review the basic methods of measurement criteria for damping properties of structures. However, we will not consider here the role of damping in dynamic behaviors such as chaos, stability, etc. Dissipation of vibratory energy takes place in both fluid and solid media, initiated by a number of possible macro activities. Accordingly, we will consider damping methods to reflect the media in which dissipation takes place when addressing damping methods in the next section. Models of fundamental dissipation mechanisms that describe energy transfer from ordered energy to disordered or thermalized energy are briefly summarized in the last section.
Open Access
Noise control engineering and education
(2021) Akay, Adnan
Open Access
Noise Control Engineering Education: Recommendations from the 2019 TQA Workshop
(Institute of Noise Control Engineering, 2021-08-01) Akay, Adnan
This paper summarizes recommendations about noise control engineering education made in a special session on noise control engineering education at NOISE-CON 2019 in San Diego and during an National Academy of Engineering (NAE)-hosted workshop under the auspices of the Technology of Quieter America (TQA) program. Speakers in both the special session and at the workshop represented industry, academe, and government emphasizing the need for more noise control engineers, the expertise required, and the areas in which they are needed. The ensuing discussions, summarized in two published reports, also point to the new technologies that affect noise control engineering education.
Open Access
Progress on consumer and industrial product noise control and technology transfer: summaries of the 2015 and 2016 TQA workshops
(Institute of Noise Control Engineering, 2021-08-01) Maling, George; Akay, Adnan; Wood, Eric W.
Progress on consumer and industrial products noise reduction, was a Technology for a Quieter America (TQA) workshop and International INCE symposium hosted by the National Academy of Engineering (NAE) held in October 2015 . The workshop consisted of two major parts, consumer products at home and commercial and industrial products. The former included appliances, waste disposers, leaf blowers, Information Technology Equipment and automotive interior noise. The second half of the workshop included such industrial products as air moving devices, industrial power generation equipment generator sets, compressor noise, transformer noise and valve plus gear noise. It also included national and international noise emission standards for consumer and industrial products. The technology transfer workshop was hosted by NAE in October 2016. The workshop covered four areas; an overview of technology transfer in the United States, government programs, technology transfer from universities, and panel discussions on a variety of topics. Government agencies which participated included NASA, the National Science Foundation, the Small Business Administration, the Federal Aviation Administration, the Office of Naval Research (ONR), and the Naval Research Laboratory.
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
Uncertainty and dissipation
(Katholieke Universiteit Leuven, 2012-09) Carcaterra, A.; Akay, Adnan
This paper discusses the question of the energy confinement in mechanical structures in the light of the uncertainties affecting the natural frequencies of the system. More precisely, recent studies have shown that energy can be introduced to a linear system with near irreversibility, or energy within a system can migrate to a subsystem nearly irreversibly, even in the absence of dissipation, provided that the system has a particular natural frequency distribution. In this paper, the case of uncertainties in the system's natural frequencies is discussed and a remarkable statistical property of the natural frequency is derived for permanent energy confinement within a part of the system. The results demonstrate the existence of a special class of linear non-dissipative dynamic systems that exhibit nearly-irreversible energy confinement (IEC) if they satisfy a minimum-variance-response (MIVAR) property. In this case, if the probability density function of the natural frequencies has a special distribution, the conservative system shows an unexpected decaying impulse response. © (2012) by the Katholieke Universiteit Leuven Department of Mechanical Engineering All rights reserved.