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Full-Text Articles in Engineering Science and Materials

Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth Aug 2018

Grain Size Effects On Viscoelastic Relaxation Of Sub-Micron Thickness Fcc Metallic Films, Jeffrey Smyth

Theses and Dissertations

Sub-micron thickness metallic thin films are known to exhibit mechanical size effects, where the thin film mechanical behavior can differ significantly from that of a bulk version of the same material. One such mechanical behavior, and the focus of this work, is the unique thin film viscoelastic deformation response to sub-yield, low-strain stimuli in near-ambient temperature environments. In engineering components using bulk materials, strains within the elastic regime are generally considered instantaneous. It is only at higher operating temperatures that temporal deformation processes, such as creep, are considered in bulk component design. However, in Micro-Electro-Mechanical Systems (MEMS), specifically Radio Frequency ...


Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian Jun 2018

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is ...


Experimental Validation For The Theory Of Blisters’ Instabilities, Hongtian Zhu Jan 2018

Experimental Validation For The Theory Of Blisters’ Instabilities, Hongtian Zhu

Mechanical Engineering Graduate Theses & Dissertations

Blister formation is a universal problem that can be witnessed within a wide range of contents. It is first documented as a side effect of syringomyelia and other diseases. Later on, the forming of blisters are also observed during the cell apoptosis, which leads to the hypothesis that it could have some intricate relationships with the death of living organisms. Other than biological problems, blister forming is also a common phenomenon in thin film technologies. Therefore, the research in the forming of blisters is essential and critical in both engineering and science fields.

In this thesis, we study the problem ...