Mechanical Engineering Commons^™

Mimicking The Mechanical Behavior Of Advancing Disc Degeneration Through Needle Injections, Jeremy S. Alsup

Theses and Dissertations

Objective - To investigate the effects of injected protease solution on the mechanical advancement of disc degeneration, and to establish test protocol for future pre-clinical validation of spinal arthroplasty devices. The hypothesis that injection of a protease into a cadaveric lumbar disc will mimic advanced degeneration mechanics was the subject of this study. Summary of Background Information - Spinal disc degeneration is a universal condition that progresses in adults due to aging, disease, or injury. Stages of disc degeneration have been categorized in cadaver specimens, with each degeneration level exhibiting characteristic changes in flexibility parameters. Spinal disc tissue can be …

A Methodology For The Extraction Of Design Principles For Unfamiliar Markets, Robert D. Campbell

Theses and Dissertations

Successful product design focuses on design principles that are relevant to a target market. Consequently, the better these principles are understood and used, the higher the likelihood that resulting products will be well-received in that market. This thesis presents a method for extracting market-specific design principles for any market. The method employs user/designer-described characteristics of products within a market to extract the design principles specific to that market. The method generalizes the product characteristics, seeks to discover design decisions that could have resulted in those characteristics, and then extracts the underlying design principles. To demonstrate the ability of the method …

Fully Compliant Mechanisms For Bearing Subtraction In Robotics And Space Applications, Ezekiel G. Merriam

Theses and Dissertations

Robotics and space applications represent areas where compliant mechanisms can continue to make a significant impact by reducing costs and weight while improving performance. Because of the nature of these applications, a common need is for bearing replacement mechanisms, or mechanisms that perform the function of a bearing without the complexity and failure modes associated with bearings. Static balancing is a design strategy that attempts to reduce the actuation effort of a mechanism, and has been applied to compliant mechanisms in some applications. Monolithic construction, especially by means of 3D printing technology, is a strategy whereby the mechanism links and …

Investigations Of Partially Immersed Spinning Spheres In A Liquid Bath And Butterfly Flight, Kenneth Roy Langley

Theses and Dissertations

This thesis examines two important problems in fluid dynamics: that of a partially immersed sphere spinning in a bath of liquid and the measurement of flow velocities around a free flying butterfly. Although the actual problems are quite different, each problem incorporates many of the same principles and techniques. When a hard-boiled egg spins through a pool of milk on the kitchen counter, the milk rises up the sides of the egg and droplets are ejected. This phenomenon occurs when any partially submerged object whose radius increases upward from the fluid surface (e.g., spheres, inverted cones, rings, etc.), spins in …

Hydrogen Storage Properties Of Magnesium Based Nanostructured Materials Produced By Glancing Angle Deposition, Mehmet Fatih Cansizoglu

Theses and Dissertations

Hydrogen is proposed as an ideal fuel for future global energy requirements with the potential to reduce carbon dioxide and other greenhouse gas emissions and improve energy independence for countries. Hydrogen is ideal for mobile applications, such as transportation vehicles and mobile devices. However storage of hydrogen remains as a challenge to realize this transition. One of the promising approaches in solid state storage is storing hydrogen in the form of metal hydrides. High hydrogen storage capacity of 7.6 wt% (weight percentage), reversibility, low cost, and abundance make magnesium an attractive material for solid state hydrogen storage. The main drawbacks …

Passive Stiffness Of Coupled Wrist And Forearm Rotations, Will Brandon Drake

Theses and Dissertations

The dynamics of wrist rotations are dominated by joint stiffness, which the neuromuscular system must account and compensate for when controlling wrist movements. Because wrist stiffness is anisotropic, movements in some directions require less torque than movements in others, creating opportunities to follow "paths of least resistance." Forearm pronation-supination (PS) can combine with wrist flexion-extension (FE) and radial-ulnar deviation (RUD) to allow the wrist to rotate in directions of least stiffness. Evaluating this hypothesis, and understanding the control of combined wrist and forearm rotations in general, requires a knowledge of the stiffness (the dominant mechanical impedance) encountered during combined wrist …

Starch Resin Moisture Level Effect On Injection Molding Processability And Molded Part Mechanical Properties With Pure Starch Resin And Polymer Blends, Jordan M. Ellingson

Theses and Dissertations

The current and forecasted global consumption of plastic packaging and products through the 21st century combined with the already reported and growing negative impact of plastics on the environment due to plastics being synthesized from nonrenewable resources that do not biodegrade is of serious concern. However, recent advances in starch technology including the development of thermoplastic starch (TPS) materials —polymers that are both renewable and biodegradable—have brought hope to reducing this impact. The mechanical properties of thermoplastic starch have often been improved by blending with synthetic polymers. One issue that arises with blending is volatilization of the melt from moisture …

Location-Allocation Optimization Of Supply Chain Distribution Networks: A Case Study, Mark Nicholas Helberg

Theses and Dissertations

The location of distribution centers is an important strategic decision in supply chain design, particularly as it relates to service quality, productivity, and profitability of the firm. There has been extensive research performed on distribution location models which require the use of complex algorithms and assumptions that make use of these models difficult in practice for small and medium enterprises (SMEs) that have limited capital and resources. Studies have also failed to capture and quantify potential business results of using more sophisticated methods. In this study, a deterministic and static location-allocation model is designed using a prototype software tool. The …

Film Cooling In Fuel Rich Environments, Jacob J. Robertson

Theses and Dissertations

The ultra compact combustor is a high performance gas turbine design concept that portends reduced weight for future weapons platforms. A natural outcome of the design is the continual presence of fuel-rich air in the turbine component of the engine. Because modern cooling schemes for hot section turbine blades involve injecting cool, oxygen-rich air adjacent to the surface, the potential arises for reaction with the unconsumed radicals in the mainstream ow and augmented heat transfer to the blade. This outcome is contrary to the purpose of film cooling, and can lead to early life-cycle turbine failure. This study examined the …

Design And Testing Of An H2/O2 Predetonator For A Simulated Rotating Detonation Engine Channel, Stephen J. Miller

Theses and Dissertations

A study is presented on the relationship between a pre-detonator and a detonation channel of an RDE. Testing was conducted on a straight narrow channel made of clear polycarbonate windows connected to an H2/O2 pre-detonator to simulate the RDE initiation scheme and allow for flow visualization. A comparison is made on decoupling distance and wave velocities for a range of pre-detonator designs, inclination angles, equivalence ratios and geometries placed within the simulated channel. Regardless of inclination angle or equivalence ratio the detonation wave decoupled within 25 mm from the pre-detonator exit into the channel. A step change in diameter 25 …

Quantifying The Nonlinear, Anisotropic Material Response Of Spinal Ligaments, Daniel J. Robertson

Theses and Dissertations

Spinal ligaments may be a significant source of chronic back pain, yet they are often disregarded by the clinical community due to a lack of information with regards to their material response, and innervation characteristics. The purpose of this dissertation was to characterize the material response of spinal ligaments and to review their innervation characteristics.


Review of relevant literature revealed that all of the major spinal ligaments are innervated. They cause painful sensations when irritated and provide reflexive control of the deep spinal musculature. As such, including the neurologic implications of iatrogenic ligament damage in the evaluation of surgical procedures …

Modeling And Simulation Study Of A Dynamic Gas Turbine System In A Virtual Test Bed Environment, Eshwarprasad Thirunavukarasu

Theses and Dissertations

Gas Turbine is a complex system and highly non linear in its overall performance. For power generation applications, it is essential to develop a reliable gas turbine model for simulating the impact on electric power generated under various load conditions. This research focuses on development of a dynamic gas turbine model to simulate both single shaft and twin shaft engines. The model is developed on a virtual test bed platform which is an advanced dynamic multidisciplinary simulation environment. The modeling approach starts by developing mathematical models for individual components of gas turbines based on the thermodynamic laws and is coupled …

Electrokinetic Mixing And Separation In Microfluidic Systems, Fang Yang

Theses and Dissertations

Electrokinetics involves the study of liquid or particle motion under the action of an electric field; it includes electroosmosis, electrophoresis, dielectrophoresis, and electrowetting, etc. The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) for use in biological and chemical assays. Here we present our works of electrokenitic based mixing and separation in microfluidics …

Synthesis And Characterization Of New Ionic And Mixed Ionic/Electronic Conductors, Kevin Gregory Romito

Theses and Dissertations

In a constantly growing and developing world, there is a great need to develop new forms of clean energy generation. Many solutions have been proposed to ameliorate these global concerns, which include fuel cell technology and new processes for reducing polluting chemicals in the atmosphere. These technologies are still in their infancy and require further development before becoming viable options.

In the case of fuel cells, particularly solid oxide fuel cells, and CO2 separation membranes, there is a need to develop ion conducting materials that are highly efficient, less costly to synthesize, and can perform strongly under many real-world conditions. …

Improved Limits And Portability Over Currently Employed Cadmium Monitoring Systems Through Preconcentration For Detection By Way Of Micro-/Nanofluidic Mechanisms, Paul F. Wach

Theses and Dissertations

Due to risk of environmental and biological accumulation of Cadmium (Cd), improved methods of early detection and monitoring must be explored as a preventative measure. Listed as one of the top three toxic heavy metals by the Environmental Protection Agency (EPA), the effects on ecological and human systems have well documented side-effects of physical mutation, reproductive sterility, kidney failure, liver disease, bone loss, and death. Found in batteries, metal plating, pigments, plastics, and cigarettes, Cd is also used as a neutron absorber in the nuclear industry as well as having 3 known radioactive isotopes. Urine Cd levels, which have been …

Modeling Ultrasonic Field Emanating From Scanning Acoustic Microscope For Reliable Characterization Of Pathogens (Biological Materials), Rowshan Ara Rima

Theses and Dissertations

Acoustic microscopy provides extraordinary advantages over state-of-the-art invasive imaging techniques to determine the mechanical properties of living colonies of pathogens and micro-organisms. It is possible to obtain the morphomechanical parameters of the pathogenic colonies e.g. variation of thickness, stiffness and the coefficients of attenuation, using scanning acoustic microscope (SAM). However, the process requires an expert with extensive understanding of SAM and ultrasonic signals which is very time consuming and expensive for complex form of analysis. Due to lack of a suitable computational tool, presently the ultrasonic wave scattering, reflection and transmission through the biological specimens cannot be properly visualized. Without …

Dual-Phase Mixed Ion And Electron Conducting Co2-Selective Permeation Membranes, Lingling Zhang

Theses and Dissertations

Fossil fuels are the dominant energy source powering our modern society. However, burning fossil fuels emits carbon dioxide (CO2), a greenhouse gas that can cause climate change and ultimately threaten the survival of humanity. Effectively mitigating CO2 emissions from the use of fossil fuels has become an intense subject of scientific research as well as political debate in recent years. The current mainstream technical approach to achieving that goal is to curb the emission of CO2 by capturing CO2 at point-sources and geologically storing it. The CO2 separation and capture process, the first step toward the ultimate storage of CO2, …

A New Class Of Solid Oxide Metal-Air Redox Batteries For Advanced Stationary Energy Storage, Xuan Zhao

Theses and Dissertations

Cost-effective and large-scale energy storage technologies are a key enabler of grid modernization. Among energy storage technologies currently being researched, developed and deployed, rechargeable batteries are unique and important that can offer a myriad of advantages over the conventional large scale siting- and geography- constrained pumped-hydro and compressed-air energy storage systems. However, current rechargeable batteries still need many breakthroughs in material optimization and system design to become commercially viable for stationary energy storage.

This PhD research project investigates the energy storage characteristics of a new class of rechargeable solid oxide metal-air redox batteries (SOMARBs) that combines a regenerative solid oxide …

Environmental Effects On Mechanical And Thermal Behaviors Of Zinc Oxide Nanobelts And Dispersion Of Carbon Nanostructures, Yingchao Yang

Theses and Dissertations

One-dimensional (1-D) nanostructures, such as nanowires, nanobelts, and nanotubes of different materials, have significant applications as nanoscale interconnects and active/functional components of electronic and optoelectronic devices, sensors, actuators, nanoelectromechanical systems (NEMS), and energy generation/conversion systems. The thermal and mechanical stabilities of those nanodevices and nanoenabled energy systems are of both theoretical and practical interests. Thermodynamic properties of nanomaterials are different from those of bulk materials. As the size of a solid particle reduces to the nanometer scale, the surface-to-volume ratio increases and the melting temperature may remarkably decrease. The functionality and/or reliability of those nanodevices and nanoenabled energy systems are …

Structural Health Monitoring Of Composite Laminates Using Piezoelectric And Fiber Optics Sensors, Catalin Roman

Theses and Dissertations

This research proposes a new approach to structural health monitoring (SHM) for composite laminates using piezoelectric wafer active sensors (PWAS) and fiber optic bragg grating sensors (FBG). One major focus of this research was directed towards extending the theory of laminates to composite beams by combining the global matrix method (GMM) with the stiffness transfer matrix method (STMM). The STMM approach, developed by Rokhlin et al (2002), is unconditionally stable and is more computationally efficient than the transfer matrix method (TMM). Starting from theory, we developed different configurations for composite beams and validated the results from the developed analytical method …

Multi-Physicochemical Modeling Of Solid Oxide Fuel Cells And Electrolyzer Cells, Yuanyuan Xie

Theses and Dissertations

Multi-physicochemical models are developed for solid oxide fuel cells and electrolysis cells. The models describe the complicated transport processes of charge (electron/ion) conservation, mass/species conservation, momentum conservation, and energy conservation. Transport processes are coherently coupled with chemical reforming processes, surface elementary reaction processes, as well as electro-oxidation processes of both hydrogen and carbon monoxide. The models are validated with experimental data and utilized for fundamental mechanism studies of SOFCs fueled with different type of fuels, such as hydrogen, hydrocarbon, e.g., methane, H2S, and their mixtures. The fundamental mechanisms associated with syngas generation using electrolysis cell are also extensively investigated using …

Welding Parameters, Distortion And Mechanical Properties Of Aa7075 Lap Joints In Ssfsw, Hejun Yu

Theses and Dissertations

Friction Stir Welding (FSW), first invented by The Welding Institute of UK (TWI) in 1991, is a solid state welding process which was initially applied to welding Aluminum Alloy. FSW has wide application in industrial sectors. Stationary shoulder friction stir welding (SSFSW) was first developed to weld low thermal conductivity Ti-based alloys, which are hard to weld using conventional friction stir welding. Previous literatures showed SSFSW can produce uniform temperature distribution through thickness during the welding process. Since SSFSW is still under study phase, its advantages and disadvantages are not yet well defined. It is important to study the characteristics …

Three-Dimensional Evolution Of Mechanical Percolation In Nanocomposites With Random Microstructures, Bethany Suzanne Fralick

Theses and Dissertations

One mechanism that is expected to play a large role in the enhanced, and sometimes novel, mechanical properties of nanocomposites is the probabilistic formation of percolated or connected microstructures. The majority of the models used to describe mechanical percolation have the functional form of a power law and depend on prior knowledge of a percolation threshold or critical volume fraction. While these models have been fairly accurate predictors of electrical conductivity in composites, they do not take any microstructural mechanisms, other than connectivity, into consideration. Classic mean-field micromechanics models, however, do not capture the variability in effective properties due to …

Microstructural-Based Modeling Of Electrical Percolation In Polymer Nanocomposites, Neelima Yellepeddi

Theses and Dissertations

Polymer nanocomposites (PNCs) represent a radical alternative to conventional filled polymers or polymer blends. In contrast to conventional composites, where the included phase is on the order of micrometers, PNCs are defined as those that have discrete constituents on the order of a few hundred nanometers. The value of PNCs is not solely based on tailoring mechanical properties, as in traditional composite design and manufacture, but rather on the potential for the design and optimization of multi-functional properties. There is major interest in these polymeric materials embedded with a conductive nanoscale filler. This is due to the possibility of designing …

Boiling And Evaporation On Micro/Nanoengineered Surfaces, Xianming Dai

Theses and Dissertations

Two-phase transport is widely used in energy conversion and storage, energy efficiency and thermal management. Surface roughness and interfacial wettability are two major impact factors for two-phase transport. Micro/nanostructures play important roles in varying the surface roughness and improving interfacial wettability. In this doctoral study, five types of micro/nanoengineered surfaces were developed to systematically study the impacts of interfacial wettability and flow structures on nucleate boiling and capillary evaporation. These surfaces include: 1) superhydrophilic atomic layer deposition (ALD) coatings; 2) partially hydrophobic and partially hydrophilic composite interfaces; 3) micromembrane-enhanced hybrid wicks; 4) superhydrophilic micromembrane-enhnaced hybrid wicks, and 5) functionalized carbon …

Toward Sophisticated Controls Of Two-Phase Transport At Micro/Nano-Scale, Fanghao Yang

Theses and Dissertations

Through the use of latent heat evaporating, flow boiling in microchannels offers new opportunities to enable high efficient heat and mass transport for a wide range of emerging applications such as high power electric/electronic/optical cooling, compact heat exchangers and reactors. However, flow boiling in microchannels is hampered by several severe constraints such as bubble confinement (e.g., slug flow), viscosity and surface tension force-dominated flows, which result in unpredictable flow pattern transitions and tend to induce severe flow boiling instabilities (i.e. low-frequency and large magnitude flows) and suppress evaporation and convection.

In this dissertation, three novel micro/nanoscale thermo-fluidic control methodologies were …

Experimental And Simulation Predicted Crack Paths For Al-2024-T351 Under Mixed-Mode I/Ii Fatigue Loading Using An Arcan Fixture, Eileen Miller

Theses and Dissertations

Mixed mode I/II fatigue experiments and simulations are performed for an Arcan fixture and a 6.35mm thick Al-2024-T351 specimen. Experiments were performed for Arcan loading angles that gave rise to a range of Mode I/II crack tip conditions from 0 ¡Ü ¦¤KII/¦¤KI ¡Ü ¡Þ. Measurements include the crack paths, loading cycles and maximum and minimum loads for each loading angle. Simulations were performed using three-dimensional finite element analysis (3D-FEA) with 10-noded tetrahedral elements via CRACK3D. While modeling the entire fixture-specimen geometry, a modified version of VCCT with automatic crack tip re-meshing and a maximum normal stress criterion were used to …

Numerical Study Of Stable Tearing Crack Growth Events Using The Cohesive Zone Model Approach, Xin Chen

Theses and Dissertations

Numerical analysis of stable tearing crack growth events plays an important role in assessing the structural integrity and residual strength of critical engineering structures. The cohesive zone model (CZM) has been widely applied to simulate fracture processes in a variety of material systems. However, its application to the study of elastic-plastic stable tearing crack growth events in ductile materials, especially under mixed-mode loading conditions, has been limited. The current study is aimed at investigating the applicability of the CZM based approach in simulating mixed-mode stable tearing crack growth events in aluminum alloys. In the simulations, which are carried out using …

Structural Origin Of Mechanical Prowess In Conch Shells, Haoze Li

Theses and Dissertations

Conch shells are natural nanocomposites with an exquisite multiscale hierarchical architecture which exhibit coupled ultrahigh mechanical strength and toughness. What materials design strategy renders conch shells such mechanical prowess? In this study, micro/nanoscale structural and mechanical characterization of conch shells (Busycon carica) has been carried out. We demonstrate, for the first time, direct evidence that the previously claimed single-crystal third-order lamellae - the basic building blocks in conch shells are essentially assembled with aragonite nanoparticles of the size ranging from 20 to 45 nm. The third-order lamellae exhibit not only elasticity but also plasticity with the strain up to 0.7% …

Synthesis And Characterization Of One Dimensional Boron-Based Nanomaterials, Rui Li

Theses and Dissertations

One dimensional (1D) metal borate and boride nanomaterials have attracted tremendous attention due to their good chemical inertness, high-temperature stability, excellent mechanical properties, and low thermal expansion coefficient.

Beta-BaB2O4 (BBO) is a well-known nonlinear optical material with a high second-order nonlinear susceptibility, wide transparency range, and high damage threshold. Using a low temperature, organic-free hydrothermal technique, single-crystalline barium polyborate Ba3B6O9(OH)6 (BBOH) nanorods were synthesized. It was found that BBO nanospindles can be achieved by annealing the BBOH nanorods at a relatively low temperature of 810 oC. Transmission electron microscopy (TEM), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS) techniques were …