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PhD Thesis Proposal: Guangchao Wan

Thursday, March 26, 2020

Rm 201 (Rett's Rm), MacLean ESC

“Bistable Structures with Defects”

Abstract

Bistable structures have two stable shapes and have a variety of applications including deployable structures, actuators, sensors, energy harvesting devices, etc. Although substantial progress has been made regarding this subject, previous works focus on the intact structures, yet few efforts have been put into the structures with defects. The quantitative understanding of the bistable structures with defects can measure the sensitivity of the structural bistability to defects and enrich the existing design space by deliberating introducing defects to cater to various application requirements.

The project will be executed by achieving three specific aims. First, through experiments, theory and finite element analysis (FEA), we study the bistability of a spherical shell with geometric defects. We quantitatively identify the relationship between the defect's size and the shell’s behaviors including bifurcation threshold, deflection and stress distribution.  Second, by introducing parallel notches on the top and bottom layers of a triple-layer plate, we design a plate structure whose bistability is driven by the equally biaxial misfit strain between the middle layer and the outside layers. We use table-top experiments to demonstrate the concept and perform FEA to verify the experimental results. These preliminary results will help us build a theoretical framework to predict the bistability within the defected plate and fabricate thermal-responsive actuators by integrating shape memory polymers or thin metals. Third, we study the snap-through of a bistable plate. The theoretical analysis demonstrates that the plate will go through a saddle-node bifurcation and thusly is subjected to the critical slowing down or “bottleneck ghost” during snap-through. The current theoretical results will be compared with FEA and experimental data in the future investigation. The analysis of this dynamic process will facilitate the analysis of the energy harvesting devices that exploit the interwell vibration of the bistable plates.

Thesis Committee

For more information, contact Daryl Laware at daryl.a.laware@dartmouth.edu.