BEGIN:VCALENDAR VERSION:2.0 PRODID:Data::ICal 0.22 BEGIN:VEVENT DESCRIPTION:Mark Robbins\, Johns Hopkins University\n\n
\n Friction affec ts many aspects of everyday life and has played a central role in technolo gy dating from the creation of fire by rubbing sticks together to current efforts to make nanodevices with moving parts. The friction "\;laws&qu ot\; we teach today date from empirical relationships observed by da Vinci and Amontons centuries ago. However\, understanding the microscopic origi ns of these laws remains a challenge. While Amontons said area was proport ional to load and independent of area\, most modern treatments assume that friction is proportional to the real area of contact where atoms on oppos ing surfaces are close enough to repel. Calculating this area is complicat ed because elastic interactions are long range and surfaces are rough on a wide range of scales. In many cases they can be described as self-affine fractals from nanometer to millimeter scales. The talk will first show tha t this complex problem has a simple solution. Dimensional analysis implies a linear relation between real contact area and load that can explain bot h Amontons'\; laws and many exceptions to them. Next the talk will expl ain why we can'\;t climb walls like spiderman even though the attractiv e interactions between atoms on our finger tips should provide enough forc e to support our weight. The talk will conclude by considering how forces in the contact area give rise to friction. Friction shows surprisingly cou nterintuitive and complex behavior in nanometer to micrometer scale contac ts and only a few explanations are consistent with macroscopic measurement s.
\n DTSTART:20151030T193000Z LOCATION:Physics Building\, Room 204 SUMMARY:A “Rough” View of Friction and Adhesion END:VEVENT END:VCALENDAR