ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4aSA3. Real and apparent dissipation of vibrations of structural systems.

J. J. McCoy

School of Eng., Catholic Univ. of America, Rm. 102, Pangborn Hall, Washington, DC 20064

Discussions of ``real'' and ``apparent'' dissipation of the vibrations of structural elements to which are attached substuctures, have suffered from a lack of precision in terminology. Identifying a real dissipation with the transformation of mechanical energy to heat and an apparent dissipation with the transformation of mechanical energy from a form that one observes to a form that one doesn't, would clarify issues. A further classification of a real dissipation as either ``resonant'' or ``nonresonant'' is suggested. A resonant dissipation is obtained for vibration frequencies that are nearly coincident with the natural frequencies of a subset of the attached subsystems. Finally, a further classification of an apparent dissipation as either ``reversible'' or ``irreversible'' is also suggested. The physics underlying the different type dissipations; their modeling; and, the dependence of measures of dissipation on more fundamental measures of the attached substructures will be discussed.