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Edward M. Kerwin

Bio: Edward M. Kerwin is an academic researcher from BBN Technologies. The author has contributed to research in topics: Viscoelasticity & Radiation damping. The author has an hindex of 5, co-authored 9 publications receiving 405 citations.

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TL;DR: In this article, the authors re-examined the definition of loss factor in terms of energy quantities, particularly as it applies to composite viscoelastic systems, and proposed simple relations which express the loss factors of series-parallel arrays of massless VRSs.
Abstract: The definition of loss factor in terms of energy quantities is re‐examined, particularly as it applies to composite viscoelastic systems. A restatement of this definition in terms of a corresponding viscoelastic spring is used to show that this definition is extremely useful for massless (ideal viscoelastic spring) systems, but may be applied unambiguously to spring systems with a single attached mass only at resonance. Simple relations are presented which express the loss factors of series‐parallel arrays of massless viscoelastic springs in terms of properties of the individual components. Implications of these relations in damping of composite structures are discussed. (This work was supported in part by the Aeronautical Systems Division, U. S. Air Force.)

319 citations

Journal ArticleDOI
TL;DR: In this article, an equivalent acoustic-dipole source was proposed to calculate the power radiated by point and line-moment excitations under conditions of heavy fluid loading, and the radiated power for a point moment excitation computed by this approach agreed with the earlier results of Thompson and Rattayya.
Abstract: Fluid loading influences the total acoustic power and the directivity of the radiation from a large, flat plate driven by localized forces. The frequency range considered here is that below the “critical” frequency. In this range, the in vacuo speed of plate flexural waves is less than the speed of sound in the adjacent fluid medium. For a point force, the directivity of the radiation field is that of a monopole for light fluid loading, but changes to that of a dipole for heavy fluid loading. Analogous behavior occurs in the case of a line force. An equivalent acoustic‐dipole source can be specified, and one can apply this equivalent‐source formalism to calculate the power radiated by point‐ and line‐moment excitations under conditions of heavy fluid loading. The radiated power for a point‐moment excitation computed by this approach agrees with the earlier results of Thompson and Rattayya. [J. Acoust. Soc. Am. 36, 1488–1490 (1964)].

34 citations

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TL;DR: In this paper, the authors analyzed the energy dissipation due to thicknesswise motion of viscoelastic layers attached to plates in order to supplement previous analyses of damping due to shear, flexural, and inplane extensional motions.
Abstract: Energy dissipation due to thicknesswise motion of viscoelastic layers attached to plates is analyzed in order to supplement previous analyses of damping due to shear, flexural, and in‐plane extensional motions. It is shown that the thicknesswise motion may constitute an important damping mechanism for relatively soft and thick viscoelastic layers at frequencies corresponding to standing‐wave resonances in the damping layer. The general behavior of thickness‐compression damping layers is discussed on the basis of a relatively simple analysis, and reasonable agreement between theory and experimental results is demonstrated.

31 citations


Cited by
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TL;DR: In this article, a single-mode nonlinear resonance acoustic spectroscopy (SIMONRAS) method was proposed to quantify the influence of mesoscopic features and damage in quasi-brittle materials.
Abstract: The presence of mesoscopic features and damage in quasi-brittle materials causes significant second-order and nonlinear effects on the acoustic wave propagation characteristics. In order to quantify the influence of such micro-inhomogeneities, a new and promising tool for nondestructive material testing has been developed and applied in the field of damage detection. The technique focuses on the acoustic nonlinear (i.e., amplitude-dependent) response of one of the material's resonance modes when driven at relatively small wave amplitudes. The method is termed single-mode nonlinear resonance acoustic spectroscopy (SIMONRAS). The behavior of damaged materials is manifested by amplitude dependent resonance frequency shifts, harmonic generation, and nonlinear attenuation. We illustrate the method by experiments on artificial slate tiles used in roofing construction. The sensitivity of this method to discern material damage is far greater than that of linear acoustic methods.

350 citations

Journal ArticleDOI
TL;DR: The sensitivity of nonlinear elastic wave spectroscopy (NEWS) methods to the detection of damage features (cracks, flaws, etc.) is far greater than can be obtained with linear acoustical methods as mentioned in this paper.
Abstract: Nonlinear elastic wave spectroscopy (NEWS) represents a class of powerful tools which explore the dynamic nonlinear stress–strain features in the compliant bond system of a micro-inhomogeneous material and link them to micro-scale damage. Hysteresis and nonlinearity in the constitutive relation (at the micro-strain level) result in acoustic and ultrasonic wave distortion, which gives rise to changes in the resonance frequencies as a function of drive amplitude, generation of accompanying harmonics, nonlinear attenuation, and multiplication of waves of different frequencies. The sensitivity of nonlinear methods to the detection of damage features (cracks, flaws, etc.) is far greater than can be obtained with linear acoustical methods (measures of wavespeed and wave dissipation). We illustrate two recently developed NEWS methods, and compare the results for both techniques on roofing tiles used in building construction.

303 citations

Journal ArticleDOI
TL;DR: In this article, a review of the available literature on damping in composite materials is presented, where a chronological review of test methods for damping estimation is presented in order to describe the time-line of theoretical knowledge development in this field.
Abstract: The present review aims at gathering the available literature on damping in composite materials. A chronological review of test methods for damping estimation is presented in order to describe the time-line of the theoretical knowledge development in this field. In the last years many new material configurations have emerged that deserve investigation, such as nano-composites, hybrid laminates and sandwich materials. Damping models specifically meant for non-homogeneous materials are reported to provide a background for understanding this problem. Although not widely exploited yet, fibre reinforced polymers has the potential to be tailored for damping by acting on constituents, geometry and boundary conditions. Nano-composites, for instance, are shown to possess a high potential for damping purposes. New hybrid and sandwich-type structures are emerging as noise and vibration control solutions in lightweight applications. The effort devoted to mathematical and numerical model in view of Finite Element integration of damping properties is also addressed. Finally, the conclusions summarise the ideas of the authors on needed steps to advance the state-of-the-art in each of the described topic.

240 citations

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TL;DR: A comprehensive review of the various research methods and theory calculation models that are employed in engineering to study the static and dynamic vibration characteristics of viscoelastic damping material (VDM) formed structures is presented in this article.

204 citations

Journal ArticleDOI
TL;DR: In this article, both linear and nonlinear (amplitude-dependent) acoustical experiments are performed on a reinforced concrete (RC) beam in which damage is gradually induced by means of static loading tests.

198 citations