Analysis of Instabilities in Microelectromechanical Systems, and of Local Water Slamming

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dc.contributor.authorDas, Kaushiken
dc.contributor.committeechairBatra, Romesh C.en
dc.contributor.committeememberPaul, Mark R.en
dc.contributor.committeememberDowling, Norman E.en
dc.contributor.committeememberHendricks, Scott L.en
dc.contributor.committeememberCramer, Mark S.en
dc.contributor.departmentEngineering Science and Mechanicsen
dc.date.accessioned2014-03-14T20:19:25Zen
dc.date.adate2009-12-09en
dc.date.available2014-03-14T20:19:25Zen
dc.date.issued2009-08-24en
dc.date.rdate2009-12-09en
dc.date.sdate2009-11-30en
dc.description.abstractArch-shaped microelectromechanical systems (MEMS) have been used as mechanical memories, micro-sensors, micro-actuators, and micro-valves. A bi-stable structure, such as an arch, is characterized by a multivalued load deflection curve. Here we study the symmetry breaking, the snap-through instability, and the pull-in instability of bi-stable arch shaped MEMS under steady and transient electric loads. We analyze transient finite electroelastodynamic deformations of perfect electrically conducting clamped-clamped beams and arches suspended over a flat rigid semi-infinite perfect conductor. The coupled nonlinear partial differential equations (PDEs) for mechanical deformations are solved numerically by the finite element method (FEM) and those for the electrical problem by the boundary element method. The coupled nonlinear PDE governing transient deformations of the arch based on the Euler-Bernoulli beam theory is solved numerically using the Galerkin method, mode shapes for a beam as basis functions, and integrated numerically with respect to time. For the static problem, the displacement control and the pseudo-arc length continuation (PALC) methods are used to obtain the bifurcation curve of arch's deflection versus the electric potential. The displacement control method fails to compute arch's asymmetric deformations that are found by the PALC method. For the dynamic problem, two distinct mechanisms of the snap-through instability are found. It is shown that critical loads and geometric parameters for instabilities of an arch with and without the consideration of mechanical inertia effects are quite different. A phase diagram between a critical load parameter and the arch height is constructed to delineate different regions of instabilities. The local water slamming refers to the impact of a part of a ship hull on stationary water for a short duration during which high local pressures occur. We simulate slamming impact of rigid and deformable hull bottom panels by using the coupled Lagrangian and Eulerian formulation in the commercial FE software LS-DYNA. The Lagrangian formulation is used to describe planestrain deformations of the wedge and the Eulerian description of motion for deformations of the water. A penalty contact algorithm couples the wedge with the water surface. Damage and delamination induced, respectively, in a fiber reinforced composite panel and a sandwich composite panel and due to hydroelastic pressure are studied.en
dc.description.degreePh. D.en
dc.identifier.otheretd-11302009-115502en
dc.identifier.sourceurlhttp://scholar.lib.vt.edu/theses/available/etd-11302009-115502/en
dc.identifier.urihttp://hdl.handle.net/10919/29809en
dc.publisherVirginia Techen
dc.relation.haspartDas_K_D_2009.pdfen
dc.rightsIn Copyrighten
dc.rights.urihttp://rightsstatements.org/vocab/InC/1.0/en
dc.subjectpull-in instabilityen
dc.subjectsymmetry breakingen
dc.subjectfluid-structure interactionen
dc.subjectlocal water slammingen
dc.subjectsnap-through instabilityen
dc.titleAnalysis of Instabilities in Microelectromechanical Systems, and of Local Water Slammingen
dc.typeDissertationen
thesis.degree.disciplineEngineering Science and Mechanicsen
thesis.degree.grantorVirginia Polytechnic Institute and State Universityen
thesis.degree.leveldoctoralen
thesis.degree.namePh. D.en

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