Identifier

etd-11072013-102139

Degree

Doctor of Philosophy (PhD)

Department

Mechanical Engineering

Document Type

Dissertation

Abstract

This dissertation provides a thermo-structural simulation for nano-scale and micro-scale structures with pinned and fixed boundary conditions which are either thermally positioned, buckled, or actuated. The study begins with simulating a pinned-pinned beam in micro-scale and nano-scale. The steady state thermo-structural equation is solved numerically using an implicit Finite Difference method implemented in Matlab to obtain the thermal positioning response, which is the thermally steady state center displacement, by adding a constant, time-independent heat flux to the structure. The results show the steady state thermal displacement of the system is a function of the geometry, pressure, material properties, and constant heat flux in the free molecular model, while this value is independent of pressure in the continuum model. The thermal positioning simulation is used to improve the thermal efficiency of a thermal micro-switch by introducing various heating configurations. The second thermal mode is thermal buckling which is used to introduce a new thermal buckling storage nano-memory. Using an unsteady simulation, the power requirements for thermal actuations, optimal geometry, and write time of the device for various materials are investigated. The results show that this memory consume a low power in the order of 1 nJ per bit and has a data storage density of 10e11 bits/cm3,which is acceptable in comparison with the current memory devices. Thermal buckling nano-memory is also radiation-protected, making it a good alternative for space exploration computer systems operating in high radiation and electromagnetic environments. In contrast with thermal positioning and buckling, thermal actuation applies time-dependent heat load leading to vibration in the structure. An implicit Finite Difference method implemented in C++ was used to solve the coupled transient thermo-structural equations with constant thermal properties, while an explicit approach was used to solve the variable properties thermo-structural equations. The response, the center displacement in a doubly-clamped bridge, is tracked by time and decomposed to the steady state and vibration amplitudes. The results show that constant thermal properties assumption is limited for small heat additions lower than 1 mW. Thermal actuation results are applicable in simulating the dynamic behavior of nano-scale devices used for switching, nano-manufacturing, and measurement.

Date

2013

Document Availability at the Time of Submission

Secure the entire work for patent and/or proprietary purposes for a period of one year. Student has submitted appropriate documentation which states: During this period the copyright owner also agrees not to exercise her/his ownership rights, including public use in works, without prior authorization from LSU. At the end of the one year period, either we or LSU may request an automatic extension for one additional year. At the end of the one year secure period (or its extension, if such is requested), the work will be released for access worldwide.

Committee Chair

Martin, Michael

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