Vibration Damping of Structural Elements

Vibration and vibration control of structures play a vital research role in mechanical, aerospace, and civil engineering, as well as many industrial and defense-related applications. To help readers fully grasp the importance of this subject, this comprehensive volume presents state-of-the-art technology in the area of vibration damping of discrete and continuous structural systems.

For years, vibration damping as a technology has been well received by various industries, however, very few books exist on this subject. In 1985, Nashif, Jones, and Henderson published an excellent book entitled Vibration Damping which provides practical and detailed information on the research and development work ranging from the fundamentals of vibration damping to design aspects in many practical applications in this subject area. Our intent is that the contents of this book be considered as a continuation of and complementary to the above work rather than competitive in the technical subject of vibration damping.

This book is intended as a reference book for aerospace, mechanical, civil, and acoustical engineers. It should also serve as a valuable reference work for graduate students, professors, and researchers in the area of Aerospace Engineering, Mechanical Engineering, and Engineering Mechanics. This book consists of eight chapters. The first three chapters address the fundamentals of vibration damping, properties of viscoelastic damping materials, vibrations of discrete damped systems, and damping of fiber-reinforced composite materials. Chapters four to seven present vibrations of damped structures for beams, plates, rings, and shells. In chapter eight, a finite element numerical method is presented to solve vibration problems of beam and plate structures with a partially attached damping treatment on the surface of the structures. The effect of initial loading is also included.

Originally, a chapter to address the vibrations of damped cylindrical shells with curved elements was planned. A series of outstanding papers on this specific subject were published by Dr. Michael El-Raheb and his colleague Mr. Paul Wagner. However, the research work was performed for their specific purposes and no numerical solutions on the vibrations of shell structures without incorporating the enclosed fluid medium was available. We regret that these materials are unable to be included in this book. Instead, we have added paragraphs pertaining to this subject topic at the end of Chapter 7 which deals with vibrations of constrained damped cylindrical shell structures.

It should be pointed out that this book deals with vibration damping characteristics of structures or systems employing damping materials. We use the properties of the viscoelastic materials in the vibration analysis, but the detailed analysis regarding their material behaviors will not be our primary concern. The book addresses the vibration damping of structural elements, and is not a materials oriented book. This book emphasizes analyses in the presentation of damped structural systems, their validations and verifications. This is done because the authors feel that analyses are the tools which not only enable us to better understand the complicated physical phenomena, but also can help calculate the physical quantities which are useful in practical applications. One might be critical of the fact that there are not enough tables and figures which may be used directly and readily for design purposes. Our reply is that much of this information for damped beam structures may be found in the book by Nashif, Jones, and Henderson. Additionally, because information pertinent to damped structures other than beams may not be available and because the vibration characteristics of damped structures depend strongly on the realistic (not assumed) properties of the damping materials employed as well as the geometrical parameters of the structures considered, we strongly believe that the presentation of "design data" should be reduced to a minimum unless the geometrical and particularly the damping material parameters of a given damped structural system are specified. Since it is technically difficult to develop and to manufacture viscoelastic materials, the damping material properties can not be assumed for materials not commercially available.

Though vibration damping technology is multi-disciplinary, the researchers and practitioners have, however, formed a rather close-knit community. In preparing this book, we would be remiss if we did not acknowledge the fact that Dr. Lynn Rogers, currently a vibration damping consultant and formerly with the Flight Dynamics Laboratory of the Air Force Wright Aeronautical Laboratories, has for years not only devoted his efforts in promoting vibration technology tirelessly, but also has organized meetings and workshops on a regular basis to provide a forum for the exchange and dissimulation of the latest state-of-the-art technology. His professional and enthusiastic efforts in advancing vibration damping technology certainly deserve our recognition.

We are very happy to take advantage of this opportunity to acknowledge the support and encouragement provided by the managers and individuals of our respective organizations in the Department of Aerospace Engineering, Mechanics and Engineering Science at the University of Florida and at the Carderock Division, and the Naval Surface Warfare Center (formerly David Taylor Research Center). Particularly, we would like to thank Dr. J. M. Bai at the University of Florida, Dr. Bruce Douglas, Director of Research, and Mr. A. J. Roscoe, at the Carderock Division for their assistance, support, and invaluable comments. Finally, the support and cooperation from the staff of Prentice Hall Publication Company, especially our editor Mr. Michael Hays in all phases of the production process are also acknowledged.

C. T. Sun, Gainesville, Florida
Y. P. Lu, Annapolis, Maryland