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Shock and Vibration
Volume 12 (2005), Issue 3, Pages 177-195

Axial Vibration Confinement in Nonhomogenous Rods

S. Choura,1 S. EL-Borgi,1 and A.H. Nayfeh2

1Applied Mechanics and Systems Research Laboratory, Tunisia Polytechnic School, B.P. 743, La Marsa 2078, Tunisia
2Department of Engineering Science and Mechanics, MC 0219, Virginia Polytechnic and State University, Blacksburg, VA 24061, USA

Received 16 January 2004; Revised 20 August 2004

Copyright © 2005 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


A design methodology for the vibration confinement of axial vibrations in nonhomogenous rods is proposed. This is achieved by a proper selection of a set of spatially dependent functions characterizing the rod material and geometric properties. Conditions for selecting such properties are established by constructing positive Lyapunov functions whose derivative with respect to the space variable is negative. It is shown that varying the shape of the rod alone is sufficient to confine the vibratory motion. In such a case, the vibration confinement requires that the eigenfunctions be exponentially decaying functions of space, where the notion of spatial domain stability is introduced as a concept dual to that of the time domain stability. It is also shown that vibration confinement can be produced if the rod density and/or stiffness are varied with respect to the space variable while the cross-section area is kept constant. Several case studies, supporting the developed conditions imposed on the spatially dependent functions for vibration confinement in vibrating rods, are discussed. Because variation in the geometric and material properties might decrease the critical buckling loads, we also discuss the buckling problem.