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Articles 721 - 750 of 1342

Full-Text Articles in Mechanical Engineering

A Hybrid Bishop-Hill Model For Microstructure Sensitive Design, Ribeka Takahashi Nov 2012

A Hybrid Bishop-Hill Model For Microstructure Sensitive Design, Ribeka Takahashi

Theses and Dissertations

A method is presented for adapting the classical Bishop-Hill model to the requirements of elastic/yield-limited design in metals of arbitrary crystallographic texture. The proposed Hybrid Bishop-Hill (HBH) model, which will be applied to ductile FCC metals, retains the `stress corners' of the polyhedral Bishop-Hill yield surface. However, it replaces the `maximum work criterion' with a criterion that minimizes the Euclidean distance between the applicable local corner stress state and the macroscopic stress state. This compromise leads to a model that is much more accessible to yield-limited design problems. Demonstration of performance for the HBH model is presented for an extensive …

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Force Optimization And Flow Field Characterization From A Flapping Wing Mechanism, Nathaniel Stephen Naegle Oct 2012

Force Optimization And Flow Field Characterization From A Flapping Wing Mechanism, Nathaniel Stephen Naegle

Theses and Dissertations

Flapping flight shows promise for micro air vehicle design because flapping wings provide superior aerodynamic performance than that of fixed wings and rotors at low Reynolds numbers. In these flight regimes, unsteady effects become increasingly important. This thesis explores some of the unsteady effects that provide additional lift to flapping wings through an experiment-based optimization of the kinematics of a flapping wing mechanism in a water tunnel. The mechanism wings and flow environment were scaled to simulate the flight of the hawkmoth (Manduca sexta) at hovering or near-hovering speeds. The optimization was repeated using rigid and flexible wings …

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Introduction Of Planar Compliant Joints Designed For Combined Bending And Axial Loading Conditions In Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby Oct 2012

Introduction Of Planar Compliant Joints Designed For Combined Bending And Axial Loading Conditions In Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby

Faculty Publications

This work introduces three joints to allow motion in lamina emergent mechanisms (LEMs) that were designed to have minimal parasitic motion under tension, compression, and a combination of tension and compression loading. Closed-form models of the joints were developed and combined with optimization algorithms for maximum flexibility in bending and then modeled using finite element analysis (FEA). The FEA results were used to predict the stiffness of the joints in bending, tension, and compression. As a baseline, lamina emergent torsional (LET) joints were designed to match the bending stiffness of each of the joints, so that the tensile-compressive performance could …

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Thermal And Mechanical Properties Of Nitrate Thermal Storage Salts In The Solid-Phase, Brian D. Iverson, Scott T. Broome, Alan M. Kruizenga, Joseph G. Cordaro Oct 2012

Thermal And Mechanical Properties Of Nitrate Thermal Storage Salts In The Solid-Phase, Brian D. Iverson, Scott T. Broome, Alan M. Kruizenga, Joseph G. Cordaro

Faculty Publications

Implementation of molten salt compounds as the heat transfer fluid and energy storage medium provides specific benefits to energy collection and conversion. Nitrate salts have been identified as a strong candidate for energy transfer and storage and have been demonstrated for use in these applications over time. As nitrate salts have solidification temperatures above ambient, concern for recovery from salt freezing events has instigated efforts to understand and predict this behavior. Accurate information of salt property behavior in the solid-phase is necessary for understanding recovery from a freeze event as well as for phase change thermal energy storage applications. Thermal …

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Spherical Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby Oct 2012

Spherical Lamina Emergent Mechanisms, Samuel E. Wilding, Larry L. Howell, Spencer P. Magleby

Faculty Publications

Lamina emergent mechanisms (LEMs) are compliant mechanisms that can be manufactured from planar materials and are capable of motion out of the plane of manufacture. Spherical LEMs combine the unique motion of spherical mechanisms with the compactness and simple topology of LEMs. The fundamentals of spherical LEMs are discussed in this work. It is found that 21 of the 33 possible spherical 4R types can be spherical LEMs. A classification based on these 21 possible types is developed. This classification is used to predict motion capabilities of spherical 6R, and Equintet mechanisms. It is also applied to arrays of spherical …

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Liquid Jet Impingement Experiments On Micro Rib And Cavity Patterned Superhydrophobic Surfaces In Both Cassie And Wenzel States, Michael G. Johnson Sep 2012

Liquid Jet Impingement Experiments On Micro Rib And Cavity Patterned Superhydrophobic Surfaces In Both Cassie And Wenzel States, Michael G. Johnson

Theses and Dissertations

Experiments were performed to characterize hydraulic jumps that form due to liquid jet impingement on superhydrophobic surfaces with alternating micro-ribs and cavities. If the surface is unimmersed, a surface tension based transition into droplets occurs, so a known depth of water was imposed downstream from the hydraulic jump to ensure the existence of a hydraulic jump. The surfaces are characterized by the cavity fraction, which is defined as the width of a cavity divided by the combined width of a cavity and an adjoining rib. Four different surface designs were studied, with respective cavity fractions of 0 (smooth surface), 0.5, …

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Effects Of Haptic And 3d Audio Feedback On Pilot Performance And Workload For Quadrotor Uavs In Indoor Environments, Robert Mark Philbrick Sep 2012

Effects Of Haptic And 3d Audio Feedback On Pilot Performance And Workload For Quadrotor Uavs In Indoor Environments, Robert Mark Philbrick

Theses and Dissertations

Indoor flight of unmanned aerial vehicles (UAVs) has many applications in environments in which it is undesirable or dangerous for humans to be, such as military reconnaissance or searching for trapped victims in a collapsed building. However, limited visual feedback makes it difficult to pilot UAVs in cluttered and enclosed spaces. Haptic feedback combined with visual feedback has shown to reduce the number of collisions of UAVs in indoor environments; however, it has increased the mental workload of the operator. This thesis investigates the potential of combining novel haptic and 3D audio feedback to provide additional information to operators of …

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Friction Stir Spot Welding Of Ultra-High Strength Steel, Trent J. Hartman Aug 2012

Friction Stir Spot Welding Of Ultra-High Strength Steel, Trent J. Hartman

Theses and Dissertations

Friction stir spot welding (FSSW) is quickly becoming a method of interest for welding of high strength steel (HSS) and ultra high strength steel (UHSS). FSSW has been shown to produce high quality welds in these materials, without the drawbacks associated with fusion welding. Tool grade for polycrystalline cubic boron nitride (PCBN) tools has a significant impact on wear resistance, weld quality, and tool failure in FSSW of DP 980 steel sheet. More specifically, for a nominal composition of 90% CBN, the grain size has a significant impact on the wear resistance of the tool. A-type tools performed the best, …

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Laboratory Experiments On Colliding Nonresonant Internal Wave Beams, Sean Paul Smith Aug 2012

Laboratory Experiments On Colliding Nonresonant Internal Wave Beams, Sean Paul Smith

Theses and Dissertations

Internal waves are prominent fluid phenomena in both the atmosphere and ocean. Because internal waves have the ability to transfer a large amount of energy, they contribute to the global distribution of energy. This causes internal waves to influence global climate patterns and critical ocean mixing. Therefore, studying internal waves provides additional insight in how to model geophysical phenomena that directly impact our lives. There is a myriad of fluid phenomena with which internal waves can interact, including other internal waves. Equipment and processes are developed to perform laboratory experiments analyzing the interaction of two colliding nonresonant internal waves. Nonresonant …

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The Effect Of Friction Stir Welding Process Parameters On Charpy V-Notch Impact Toughness In Hsla-65, Samuel C. Sanderson Aug 2012

The Effect Of Friction Stir Welding Process Parameters On Charpy V-Notch Impact Toughness In Hsla-65, Samuel C. Sanderson

Theses and Dissertations

HSLA-65 steel (6.4 mm thick) was friction stir welded at various welding speeds and spindle speeds. Varying weld parameters provided a range of heat inputs. Impact toughness was evaluated as a function of the different weld parameters and corresponding weld heat inputs. Charpy V-Notch (CVN) tests were conducted in parent material and at both the weld nugget centerline and heat-affected zone (HAZ) locations. The upper shelf CVN impact energy of the weld nugget was above that of the base metal for all weld parameters. The upper shelf impact toughness in the HAZ was largely unaffected by changing weld parameters. The …

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The Extraction Of Shock Waves And Separation And Attachment Lines From Computational Fluid Dynamics Simulations Using Subjective Logic, Matthew C. Lively Aug 2012

The Extraction Of Shock Waves And Separation And Attachment Lines From Computational Fluid Dynamics Simulations Using Subjective Logic, Matthew C. Lively

Theses and Dissertations

The advancement of computational fluid dynamics to simulate highly complex fluid flow situations have allowed for simulations that require weeks of computation using expensive high performance clusters. These simulations often generate terabytes of data and hinder the design process by greatly increasing the post-processing time. This research discusses a method to extract shock waves and separation and attachment lines as the simulation is calculating and as a post-processing step. Software agents governed by subjective logic were used to make decisions about extracted features in converging and converged data sets. Two different extraction algorithms were incorporated for shock waves and separation …

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Study On The Fracture Toughness Of Friction Stir Welded Api X80, Allan M. Tribe Aug 2012

Study On The Fracture Toughness Of Friction Stir Welded Api X80, Allan M. Tribe

Theses and Dissertations

High strength low alloy (HSLA) steels have been developed to simultaneously have high yield strength and high fracture toughness. However, in practical applications steel must be welded. Traditional arc welding has proven detrimental to the fracture toughness of HSLA steels. Friction stir welding has recently shown mixed results in welding HSLA steels. The range of welding parameters used in these recent studies however has been very limited. With only a few welding parameters tested, the effect of spindle speed, travel speed, and heat input on the fracture toughness of friction stir welded HSLA steel remains unknown. To understand how the …

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Mathematical Model And Experimental Exploration Of The Nanoinjector Lance Array, Nathan C. Toone Jul 2012

Mathematical Model And Experimental Exploration Of The Nanoinjector Lance Array, Nathan C. Toone

Theses and Dissertations

The Nanoinjector Lance Array has been developed to inject foreign material into thousands of cells at once using electrophoresis to attract and repel particles to and from the electrically-charged lances. A mathematical computer model simulating the motion of attracted or repelled proteins informs the design of the nanoinjection lance array system. The model is validated by accurately predicting protein velocity in electrophoresis experiments. A complete analysis of parameters is conducted via simulations and specific research questions regarding the counter electrode of the nanoinjector lance array system are explored using the model. A novel technique for fabricating lance arrays from collapsed …

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Design And Testing Of A Biological Microelectromechanical System For The Injection Of Thousands Of Cells Simultaneously, Gregory Herlin Teichert Jul 2012

Design And Testing Of A Biological Microelectromechanical System For The Injection Of Thousands Of Cells Simultaneously, Gregory Herlin Teichert

Theses and Dissertations

The ability to inject DNA and other foreign particles into cells, both germ cells (e.g. to produce transgenic animals) and somatic cells (e.g. for gene therapy), is a powerful tool in genetic research. Nanoinjection is a method of DNA delivery that combines mechanical and electrical methods. It has proven to have higher cell viability than traditional microinjection, resulting in higher integration per injected embryo. The nanoinjection process can be performed on thousands of cells simultaneously using an array of microneedles that is inserted into a monolayer of cells. This thesis describes the needle array design requirements and the fabrication process …

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The Biomechanical Implications Of An Intrinsic Decompressive Pre-Load On A Posterior Dynamic Stabilization System, Jeffrey Ellis Harris Jul 2012

The Biomechanical Implications Of An Intrinsic Decompressive Pre-Load On A Posterior Dynamic Stabilization System, Jeffrey Ellis Harris

Theses and Dissertations

The purpose of this research was to investigate the influence of applying an intrinsic decompressive pre-load to a particular dynamic stabilization device on the biomechanical response of the lumbar spine. The FlexSPAR, which supports this ability, was used as a test case. A finite element model of a full lumbar spine was developed and validated against experimental data, and tested in the primary modes of spinal motion. The model was used to compare five lumbar spine test cases: healthy, degenerate, implanted with a pre-loaded device, implanted with a device without a pre-load, and implanted with rigid fixators. Results indicated that …

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Data Consistency And Conflict Avoidance In A Multi-User Cax Environment, Robert Aaron Moncur Jul 2012

Data Consistency And Conflict Avoidance In A Multi-User Cax Environment, Robert Aaron Moncur

Theses and Dissertations

This research presents a new method to preserve data consistency in a multi-user CAx environment. The new method includes three types of constraints which work by constraining and controlling both features and users across an entire multi-user CAx platform. The first type of constraint includes locking or reserving features to enable only one user at a time to edit a given feature. The second type of constraint, collaborative feature constraints, allows flexible constraining of each individual feature in a model, and the data that defines it. The third type of constraint, collaborative user constraints, allows the constraining of user permissions …

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A Comparative Study Of Strength And Stiffness Of Thin-Walled Specimens Fabricated By Fdm And 3d Printing Technologies, Miranda Rodrigo Jul 2012

A Comparative Study Of Strength And Stiffness Of Thin-Walled Specimens Fabricated By Fdm And 3d Printing Technologies, Miranda Rodrigo

Theses and Dissertations

Rapid Prototyped part failure constitutes a major issue for both RP providers and customers. When parts fail the reputation of the vendor is heavily deteriorated, customer dissatisfaction increase and replacement of the broken parts is often necessary to avoid the loss of future business. Product design teams often run into situations where Rapid Prototyped parts are not able to withstand shipping and handling and delivered broken or while demonstrating and examining the parts. When done in the face of customers this builds a perception of poor quality and lack of aptitude on the design group as well as the RP …

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Analytical Thermal Model Of Friction Stir Welding With Spatially Distributed Heat Source, Gordon Scott Reese Jul 2012

Analytical Thermal Model Of Friction Stir Welding With Spatially Distributed Heat Source, Gordon Scott Reese

Theses and Dissertations

Friction stir welding (FSW) has been studied extensively for the past two decades. Thermal modeling has been of particular interest, as the quality of the weld is dependent upon the temperature history of the work piece during the process. Since direct temperature measurements of the welded zone are not possible, an analytical model was developed to predict the temperature in this area. This model requires parameters that cannot be easily experimentally determined, so a best fit for these parameters was acquired via regression analysis by comparing the model to experimental data acquired outside of the weld zone. The model was …

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Measurement And Analysis Of Gas Composition In A Staged And Unstaged Oxy-Fired Pulverized Coal Reactor With Warm Flue Gas Recycle, Skyler Charles Chamberlain Jul 2012

Measurement And Analysis Of Gas Composition In A Staged And Unstaged Oxy-Fired Pulverized Coal Reactor With Warm Flue Gas Recycle, Skyler Charles Chamberlain

Theses and Dissertations

Nearly half of the electrical power produced in the United States is generated with coal. Coal power is inexpensive and reliable, but coal combustion releases harmful pollutants including NOx and SOx into the atmosphere if not controlled. CO2, a greenhouse gas, is also released during coal combustion and may contribute to global warming. A promising technology enabling carbon capture is oxy-coal combustion. During oxy-combustion, coal is burned in an atmosphere of O2 and recycled flue gas to eliminate nitrogen which makes up the majority of air-combustion flue gas. Oxy-combustion flue gas is mainly composed of CO2 and H2O. H2O can …

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Investigation Of Internal Wave Spectra Due To Observed Interactions, Benjamin Lee Hillyard Jul 2012

Investigation Of Internal Wave Spectra Due To Observed Interactions, Benjamin Lee Hillyard

Theses and Dissertations

Observational data are analyzed and decomposed to reveal internal ocean waves and their interactions with one another. Particularly, the interaction of small-scale internal waves with a large inertia wave packet is examined. Using the governing internal wave equations, an analysis is made of the energy propagation of a small scale internal wave with a large-scale inertia wave. With that, an assessment is made of the frequency of occurrence of various encounter types. Next, the possibility of energy transfer during an interaction is explored. The relative energy of the small wave before interacting with the large-scale inertia wave is calculated and …

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Modeling Of Complex Pentahedron Solar Still Covers To Optimize Distillate, Jeremy D. Lefevre Jul 2012

Modeling Of Complex Pentahedron Solar Still Covers To Optimize Distillate, Jeremy D. Lefevre

Theses and Dissertations

This work shows the results of modeling and optimizing pentahedron-shaped covers for application on a passive solar still. While modeling under the assumption of clear weather in Provo, Utah, United States of America, it was found that two main geometries resulted: A single slope still with fully vertical back and sidewalls and a south face tilted at 37.1°, absorbing a total of 8.98 megajoules of direct solar radiation. A half-pyramid shaped cover with vertical backwall, sidewalls tilted in at 60.6°, and a south face tilted in at 41.5°, absorbing 9.34 megajoules of direct solar radiation.With improved covers, solar radiation absorbed …

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Three Dimensional Characterization Of Vocal Fold Fluid Structure Interactions, Joseph R. Nielson Jul 2012

Three Dimensional Characterization Of Vocal Fold Fluid Structure Interactions, Joseph R. Nielson

Theses and Dissertations

Voice quality is strongly linked to quality of life; those who suffer from voice disorders are adversely affected in their social, family, and professional relationships. An effort has been made to more fully understand the physics behind how the voice is created, specifically the fluid structure interactions that occur during vocal fold vibration. Many techniques have been developed and implemented to study both the motion of the vocal folds and the airflow that creates the motion. Until recently these techniques have sought to understand a highly three-dimensional phenomenon with 1D or 2D perspectives.This research focuses on the development and implementation …

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Investigation Of A Planetary Differential For Use As A Continuously Variable Transmission, Austin B. Randall Jul 2012

Investigation Of A Planetary Differential For Use As A Continuously Variable Transmission, Austin B. Randall

Theses and Dissertations

With gas prices on the rise, the demand for high-mileage and low pollution vehicles has taken on an unprecedented role in our society. The production and implementation of electric and hybrid-electric vehicles has recently been a large focus of all major automobile manufacturers. Although these new vehicles have begun to solve much of the expensive fuel consumption and air pollution problems that our economy faces, the initial cost of these vehicles has proven to still be too expensive to capture a significant portion of the market. The further advancement of this technology must not only continue to focus on better …

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Investigation Of Compliant Space Mechanisms With Application To The Design Of A Large-Displacement Monolithic Compliant Rotational Hinge, Robert Mcintyre Fowler Jun 2012

Investigation Of Compliant Space Mechanisms With Application To The Design Of A Large-Displacement Monolithic Compliant Rotational Hinge, Robert Mcintyre Fowler

Theses and Dissertations

The purpose of this research is to investigate the use of compliant mechanisms in space applications and design, analyze, and test a compliant space mechanism. Current space mechanisms are already highly refined and it is unclear if significant improvements in performance can be made by continuing to refine current designs. Compliant mechanisms offer a promising opportunity to change the fundamental approach to achieving controlled motion in space systems and have potential for dramatic increases in mechanism performance given the constraints of the space environment. A compliant deployment hinge was selected for development after industry input was gathered. Concepts for large-displacement …

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Multi-User Methods For Fea Pre-Processing, Prasad Weerakoon Jun 2012

Multi-User Methods For Fea Pre-Processing, Prasad Weerakoon

Theses and Dissertations

Collaboration in engineering product development leads to shorter product development times and better products. In product development, considerable time is spent preparing the CAD model or assembly for Finite Element Analysis (FEA). In general Computer-Aided Applications (CAx) such as FEA deter collaboration because they allow only a single user to check out and make changes to the model at a given time. Though most of these software applications come with some collaborative tools, they are limited to simple tasks such as screen sharing and instant messaging. This thesis discusses methods to convert a current commercial FEA pre-processing program into a …

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Evaluation Of Advanced Conductive Nickel Materials For Strain Sensing In Carbon Fiber Reinforced Polymers, Michael Christian Koecher Jun 2012

Evaluation Of Advanced Conductive Nickel Materials For Strain Sensing In Carbon Fiber Reinforced Polymers, Michael Christian Koecher

Theses and Dissertations

Due to their unique properties, carbon fiber reinforced polymers (CFRP) are becoming ever more prevalent in today's society. Unfortunately, CFRP suffer from a wide range of failure modes and structural health monitoring methods are currently insufficient to predict these failures. It is apparent that self-sensing structural health monitoring could be advantageous to protect consumers from catastrophic failure in CFRP structures. Previous research has shown that embedded nickel nanostrand nanocomposites can be used to instantaneously measure strain in carbon fiber composites, but these methods have been severely limited and can induce high stress concentrations that compromise the structural integrity of the …

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Microscopic Light Field Particle Image Velocimetry, Bryce Adam Mcewen Jun 2012

Microscopic Light Field Particle Image Velocimetry, Bryce Adam Mcewen

Theses and Dissertations

This work presents the development and analysis of a system that combines the concepts of light field microscopy and particle image velocimetry (PIV) to measure three-dimensional velocities within a microvolume. Rectanglar microchannels were fabricated with dimensions on the order of 350-950 micrometers using a photolithographic process and polydimethylsiloxane (PDMS). The flow was seeded with fluorescent particles and pumped through microchannels at Reynolds numbers ranging from 0.016 to 0.028. Flow at Reynolds numbers in the range of 0.02 to 0.03 was seeded with fluorescent particles and pumped through microchannels. A light field microscope with a lateral resolution of 6.25 micrometers and …

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The Composition And Morphology Of Coal Ash Deposits Collected In An Oxy-Fuel, Pulverized Coal Reactor, Curtis K. Stimpson May 2012

The Composition And Morphology Of Coal Ash Deposits Collected In An Oxy-Fuel, Pulverized Coal Reactor, Curtis K. Stimpson

Theses and Dissertations

Coal ash deposits were collected in a 160 kWth, down-fired oxy-coal reactor under staged and unstaged conditions for four different coals (PRB, Gatling, Illinois #6, and Mahoning). Concentration measurements of carbon, oxygen, sodium, magnesium, aluminum, silicon, phosphorus, sulfur, chlorine, potassium, calcium, titanium, chromium, manganese, iron, nickel, strontium, and barium were gathered from each deposit sample using scanning electron microscopy and energy dispersive spectroscopy (SEM-EDS). Backscattered electron micrographs for each deposit sample were analyzed to gather morphological data. Particle size and shape were studied for each deposit collected. The average particle sizes of the particles in upstream deposits were much larger …

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Mechanical Properties And Mems Applications Of Carbon-Infiltrated Carbon Nanotube Forests, Walter C. Fazio May 2012

Mechanical Properties And Mems Applications Of Carbon-Infiltrated Carbon Nanotube Forests, Walter C. Fazio

Theses and Dissertations

This work explores the use of carbon-infiltrated carbon nanotube (CI-CNT) forests as a material for fabricating compliant MEMS devices. The impacts of iron catalyst layer thickness and carbon infiltration time are examined. An iron layer of 7nm or 10nm with an infiltration time of 30 minutes produces CI-CNT best suited for compliant applications. Average maximum strains of 2% and 2.48% were observed for these parameters. The corresponding elastic moduli were 5.4 GPa and 4.1 GPa, respectively. A direct comparison of similar geometry suggested CI-CNT is 80% more flexible than single-crystal silicon. A torsional testing procedure provided an initial shear modulus …

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No, Burnout, Flame Temperature, Emissivity, And Radiation Intensity From Oxycombustion Flames, Darrel Patrick Zeltner May 2012

No, Burnout, Flame Temperature, Emissivity, And Radiation Intensity From Oxycombustion Flames, Darrel Patrick Zeltner

Theses and Dissertations

This work produced the retrofit of an air-fired, 150 kW reactor for oxy-combustion which was then used in three oxy-combustion studies: strategic oxy-combustion design, oxy-combustion of petroleum coke, and air versus oxy-combustion radiative heat flux measurements. The oxy-combustion retrofit was accomplished using a system of mass flow controllers and automated pressure switches which allowed safe and convenient operation. The system was used successfully in the three studies reported here and was also used in an unrelated study. A study was completed where a novel high oxygen participation burner was investigated for performance while burning coal related to flame stability, NO, …

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