Department of Physics
September 3, 2003
Willet Science Center 101
"Friction, friction everywhere but in our understanding!"Abstract: Physics has been very successful in describing nature where the length scale is of the order of an angstrom (or even a hundred thousand times smaller). In the million-fold separation of the atomic-scale from the macro-scale of our senses--lies a mesoscale, which in comparison to other research is virtually unstudied. It is a baffling world of defect organization, which the speaker believes to be the basis for most types of friction. Many and probably the most notable of mesoscale characteristics were observed by accident. These include
(i) the shape memory alloy Nitinol in the early 1960's,
(ii) the 'suspension effect' of high-Tc superconductors in the late 1980's [Mod. Phys. Lett. B2, 1027 (1988), described at http://www.brookscole.com/physics_d/templates/student_resources/003026961X_serway/optional/levitation.html],
and (iii) 'acoustical memory' in a crystal of LiNbO3 in the last two years (Phys, Rev. Lett. 89, 115506, 2002; described at http://www.nature.com/nsu/020916/020916-19.html).
The portion of this talk concerned with (i) nitinol (http://arXiv.org/html/physics/0308077) is based on Peters' recent study of this unusual alloy that may even be present in your eyeglass frames (called 'titanium' in the optician's world). The discussion of each of (ii) the suspension effect, and (iii) the acoustic memory effect, will include some personal stories; since there is a relationship of the principal investigator to the speaker as (ii) brother, and (iii) PhD director.
All the phenomena will be discussed in the context of friction, from a unifying perspective--that "when mother nature fills the vacuum she abhors, she rarely does so with perfection". Her defect building blocks operate collectively at the mesoscale, and the synergy of their interactions is yet to be explained from first principles.
The challenge to our understanding of such matters will be illustrated with a decades-old demonstration (described in 1952 by B. Gross, "The flow of Solids", Physics Today, Vol. 5, No. 8, p. 6). The essence of this simple demo was rediscovered in the last decade by LIGO personnel. Those who are searching for gravitational waves have labeled it the 'anelastic aftereffect'. Being responsible for internal friction noise, it has placed serious limitations on the sensitivity of their interferometer.
join us for light refreshments outside WSC 109 at 4:15.
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