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Articles 1 - 7 of 7
Full-Text Articles in Mechanical Engineering
Experimental Investigation Of The Vortex-Induced Vibration Response Of A Flexibly-Mounted Rigid Cylinder In The Shear-Thinning And Inertial-Viscoelastic Flow Regimes, Pieter Boersma
Doctoral Dissertations
Flexible or flexibly-mounted structures with bluff cross-sections in flow can shed vortices at frequencies that increase with increasing flow velocity. When this shedding frequency is equal to the structure's natural frequency, the structure can oscillate. This is called vortex-induced vibrations (VIV). VIV is present in multiple fluid-structure interaction (FSI) systems which can be found in industrial, medical, and engineering applications. These oscillations can be desirable or undesirable, so understanding the physics behind this phenomenon is important. This work seeks to investigate experimentally the VIV response in the inertial-viscoelastic regime where fluid inertia and elasticity influence the system. The subcritical Newtonian …
Advanced Materials Design Using Application-Based Processing Techniques, Daniel S. Camarda
Advanced Materials Design Using Application-Based Processing Techniques, Daniel S. Camarda
Doctoral Dissertations
This dissertation pertains to generating advanced materials using application-based processing techniques. First, billets consisting of PTFE sintering powders are evaluated using Thermomechancal Analysis. It was found that both shape change and volume change are associated with enthalpic and entropic recoil, respectively. These phenomena, due to melting and stored energy during the powder compaction process, were found to be molecular weight dependent. Additionally, kinetics of the recovery and sintering process were found to be slower in blended specimens than pure samples. Next, the creation of graft copolymers by selectively grafting a second polymer to the amorphous fraction of a semi-crystalline polymer …
Experimental Study Of Viscoelastic Fluid-Structure Interactions, Anita Anup Dey
Experimental Study Of Viscoelastic Fluid-Structure Interactions, Anita Anup Dey
Doctoral Dissertations
It is well known that when a flexible or flexibly-mounted structure is placed perpendicular to a Newtonian fluid flow, it can oscillate due to the shedding of vortices at high Reynolds numbers. Unlike Newtonian fluids, viscoelastic fluid flow can become unstable even at infinitesimal Reynolds numbers due to a purely elastic flow instability occurring at large Weissenberg numbers. This thesis focuses on exploring the mechanisms of viscoelastic fluid-structure interactions (VFSI) through experimental investigations on several different combinations of flexible and flexibly-mounted circular cylinders, micro and macro-scale cantilevered beams and viscoelastic fluids such as wormlike micelle solutions and polymer solutions. VFSI …
Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim
Polymeric Impulsive Actuation Mechanisms: Development, Characterization, And Modeling, Yongjin Kim
Doctoral Dissertations
Recent advances in the field of biomedical and life-sciences are increasingly demanding more life-like actuation with higher degrees of freedom in motion at small scales. Many researchers have developed various solutions to satisfy these emerging requirements. In many cases, new solutions are made possible with the development of novel polymeric actuators. Advances in polymeric actuation not only addressed problems concerning low degree of freedom in motion, large system size, and bio-incompatibility associated with conventional actuators, but also led to the discovery of novel applications, which were previously unattainable with conventional engineered systems. This dissertation focuses on developing novel actuation mechanisms …
The Rheology And Roll-To-Roll Processing Of Shear-Thickening Particle Dispersions, Sunilkumar Khandavalli
The Rheology And Roll-To-Roll Processing Of Shear-Thickening Particle Dispersions, Sunilkumar Khandavalli
Doctoral Dissertations
Particle dispersions are ubiquitous in our daily lives ranging from food and pharmaceutical products to inks. There has been great interest in the recent years in formulation of functional inks to fabricate myriad flexible electronic devices through high-throughput roll-to-roll technologies. The formulations often contain several functional additives or rheological modifiers that can affect the microstructure, rheology and processing. Understanding the rheology of formulations is important for tuning the formulation for optimal processing. This thesis presents investigations on the rheology of particle dispersions and their impact on roll-to-roll technologies. Shear-thickening behavior is common in particle dispersions, particularly, concentrated particulate inks. We …
Polymer And Small Molecule Designs For Anion Conducting Membranes: Connected Ion-Channel Morphologies And Highly Alkaline Stable Ammonium Cations, Sedef P. Ertem
Doctoral Dissertations
Fuel cells are one of the oldest sustainable energy generation devices, converting chemical energy into electrical energy via reverse-electrolysis reactions. With the rapid development of polymer science, solid polymer electrolyte (SPE) membranes replaced the conventional liquid ion transport media, rendering low-temperature fuel cells more accessible for applications in portable electronics and transportation. However, SPE fuel cells are still far from commercialization due to high operation cost, and insufficient lifetime and performance limitations. Anion exchange membrane fuel cells (AEMFCs) are inexpensive alternatives to current proton exchange membrane fuel cell (PEMFC) technology, which relies on utilizing expensive noble-metal catalysts and perfluorinated SPE …
Scaling Reversible Adhesion In Synthetic And Biological Systems, Michael David Bartlett
Scaling Reversible Adhesion In Synthetic And Biological Systems, Michael David Bartlett
Open Access Dissertations
Geckos and other insects have fascinated scientists and casual observers with their ability to effortlessly climb up walls and across ceilings. This capability has inspired high capacity, easy release synthetic adhesives, which have focused on mimicking the fibrillar features found on the foot pads of these climbing organisms. However, without a fundamental framework that connects biological and synthetic adhesives from nanoscopic to macroscopic features, synthetic mimics have failed to perform favorably at large contact areas. In this thesis, we present a scaling approach which leads to an understanding of reversible adhesion in both synthetic and biological systems over multiple length …