Nonlinear Mechanics, Morphology and Instability of Thin Structures

Series: 
Other Talks
Tuesday, October 9, 2012 - 13:00
1 hour (actually 50 minutes)
Location: 
MRDC Building, Room 4211
,  
Washington University in St. Louis
Organizer: 

<a href="http://www2.me.gatech.edu/www/calendar/view_seminar.asp?speaker=Zi%20Che... target="_blank">Speaker's Bio</a>.
Host: David Hu, School of Mechanical Engineering

Mechanical forces play a key role in the shaping of versatile morphologies of thin structures in natural and synthetic systems. The morphology and deformation of thin ribbons, plates and rods and their instabilities are systematically investigated, through both theoretical modeling and table-top experiments. An elasticity theory combining differential geometry and stationarity principles is developed for the spontaneous bending and twisting of ribbons with tunable geometries in presence of mechanical anisotropy. Closed-form predictions are obtained from this theory with no adjustable parameters, and validated with simple, table-top experiments that are in excellent agreement with the theoretical predictions. For large deformation of ribbons and plates, a more general theory is developed to account for mechanical instability (slap-bracelet type) induced by geometric nonlinearity, due to the competition between inhomogeneous bending and mid-plane stretching energy. This comprehensive, reduced parameter model leads to unique predictions about multistability that are validated with a series of table-top experiments. Furthermore, this study has been extended to interpret a different type of snap-through instability that the Venus flytrap has been actively employing to capture insects for millions of years, and the learnt principle is used to guide the design of bio-mimetic flytrap robot.