MechE PhD Prospectus Defense - Lucia Stein-Montalvo

  • Starts: 10:00 am on Monday, December 17, 2018
  • Ends: 12:00 pm on Monday, December 17, 2018
TITLE: INTERFACES AND INSTABILITIES OF ELASTIC SHELLS. COMMITTEE: Prof. Douglas Holmes (ME/MSE) (Advisor) Prof. Harold Park (ME/MSE) Prof. Paul Barbone (ME/MSE) Prof. Sheila Russo (ME/MSE) ABSTRACT: In this era of advanced, shape-shifting materials, an understanding of elastic in­ stabilities will provide a pathway to choosing and controlling shape change. Thin structures like rods, plates, and shells are especially prone to instabilities, which may be induced by external forces, confinement, or pressure, but also by non-mechanical stimuli, such as heating, differential growth, or swelling. Tying this range of stim­ uli together is the fact that a structure's mechanical behavior - the way it responds to stimuli or constraints - is inseparable from its geometry. A notable effect of ge­ ometry is that the edges of these thin bodies, and the way they interact with their surroundings, are of particular importance. The first two projects covered in this prospectus are aimed at unraveling the ge­ ometric reasons certain confining boundaries can dramatically change the nature of instabilities. First, we study the periodic buckling patterns that emerge when moder­ ately thick shells are subjected to in-plane and transverse confinement. With experi­ ments, simulations, and a simple model, we learn that a single geometric parameter predicts the wavenumber. Outstanding questions about the role of stretching primarily motivate the next study, where we see that in-plane and packing-type confinement together cause thin, flexible plates to wrinkle as well. The later topics move toward controlling what happens at the boundaries of shells, so as to select mechanical instabilities for enhanced functionality. In snap­ ping spherical caps, we examine the nonlinear trade-off between the magnitude of a non-mechanical, curvature-inducing stimulus, and the size of the sensitive boundary region to which it is applied. This has implications for optimizing actuator efficiency. Finally, we introduce the possibility of steering a mechanical swimmer - a hollow sphere - through a liquid by fine-tuning pressure cycles to drive buckling behavior.
Location:
110 Cummington Mall, Room ENG 245