August 28, 2002
Willet Science Center 109
(Overflow to WSC 101 if necessary…)
“Foundations and Frontiers of Damping Physics”
Abstract: Oscillator energy loss is foundational to much of physics; for example, in the contributions of H. A. Lorentz to atomic physics and G. G. Stokes to fluid physics. Perhaps best known to engineers because of his and Navier’s equations of fluid mechanics; Stokes’ law of viscous drag is basic to Robert Millikan’s famous experiment to determine the charge of the electron. It is not well known that Stokes developed his law of viscous drag from considerations of pendulum damping. In the 21st century, mechanical oscillator damping continues to be important in fundamental experiments; such as LIGO’s pursuit of the elusive gravitational wave, and resolving errors in the estimate of Newton’s universal gravitational constant. The damping most important to present endeavors is that which derives from the ‘dirty’ physics of stress-strain hysteresis. Recent studies suggest that Leonardo da Vinci and Charles Augustin Coulomb may have laid a better foundation than anybody realized. For example, it is possible to easily modify Coulomb’s famous law of sliding friction to accommodate, with one equation, several different damping cases known to structural engineers and geoscientists. Mercer’s experiments directed “Toward a universal model of damping—modified Coulomb friction” will be described, with an emphasis on the importance of the model’s nonlinearity.
join us for light refreshments at 4:15.
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