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Masters Theses

2012

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Articles 1 - 29 of 29

Full-Text Articles in Mechanical Engineering

Validation Of Weak Form Thermal Analysis Algorithms Supporting Thermal Signature Generation, Elton Lewis Freeman Dec 2012

Validation Of Weak Form Thermal Analysis Algorithms Supporting Thermal Signature Generation, Elton Lewis Freeman

Masters Theses

Extremization of a weak form for the continuum energy conservation principle differential equation naturally implements fluid convection and radiation as flux Robin boundary conditions associated with unsteady heat transfer. Combining a spatial semi-discretization via finite element trial space basis functions with time-accurate integration generates a totally node-based algebraic statement for computing. Closure for gray body radiation is a newly derived node-based radiosity formulation generating piecewise discontinuous solutions, while that for natural-forced-mixed convection heat transfer is extracted from the literature. Algorithm performance, mathematically predicted by asymptotic convergence theory, is subsequently validated with data obtained in 24 hour diurnal field experiments for ...


Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa Dec 2012

Heat Transfer Analysis Via Rate Based Sensors, Jake Erik Plewa

Masters Theses

This work presents an integrated rate-based sensor and method for resolving the surface heat flux of a fundamental inverse heat conduction problem without numerical regularization or differentiation in a semi-infinite geometry that additionally accounts for thermocouple delay due to its intrinsic time constant. The sensor uses well-designed analog filters to directly regularize raw voltage data to eliminate the need for numerical regularization methods. The sensor can also be used in a series of well-designed voltage-rate interfaces that directly measure the voltages from in-depth thermocouples, which are used in conjunction with the thermocouple calibration curve to provide higher-time derivatives of the ...


Reduced Leak Calibration Uncertainties By The Outgassing Quantification Method, Philip Mason Carper May 2012

Reduced Leak Calibration Uncertainties By The Outgassing Quantification Method, Philip Mason Carper

Masters Theses

Standard leaks are used throughout industry for various applications, such as gas transfer, calibration of mass spectrometers, and calibration of leak detectors. The ability to provide a controlled delivery of gases at relatively low flow rates makes standard leaks a popular choice for calibration standards. This ability also allows for precise quantities of gas to accumulate over time. The accumulation of gas from standard leaks is used as a “transfer standard” for making in-process adjustments to measurement instrumentation. With the advent of tighter quality control constraints, the quantification and control of leak rates is becoming an increasingly important matter, placing ...


Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke May 2012

Droplet Characterization In The Wake Of Steam Turbine Cascades, Adam Charles Plondke

Masters Theses

In low-pressure steam turbines, water droplet formation on the surfaces of stationary stator blades can lead to erosion on downstream turbine blades and other equipment. One property that affects the size of the droplets that are formed is the adhesive forces between the water and the surface of the stator blade. The adhesive forces hold the droplets to the surface where they may combine, forming increasingly larger droplets. Eventually, the aerodynamic forces will tear the droplets off the surface, carrying them downstream.

To study the effect of stator surface properties on the droplet size distribution, four cascades of stator blades ...


A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst May 2012

A Method For Performance Analysis Of A Ramjet Engine In A Free-Jet Test Facility And Analysis Of Performance Uncertainty Contributors, Kevin Raymond Holst

Masters Theses

Ramjet and scramjet engines are being developed to provide a more fuel efficient means of propulsion at high Mach numbers. Part of the development of these engines involves test and evaluation of an engine in ground facilities as well as in flight. Ground facilities, like Arnold Engineering Development Center (AEDC) and those at engine manufacturers like General Electric (GE) and Pratt & Whitney (PW), have decades of experience testing traditional turbine engines and much less experience testing full scale ramjet engines.

Testing a supersonic engine model in a free-jet mode presents a host of challenges not experienced during traditional direct connect ...


A Gps-Based Mobility Power Model For Military Vehicle Applications, George William Bozdech May 2012

A Gps-Based Mobility Power Model For Military Vehicle Applications, George William Bozdech

Masters Theses

In recent years, military vehicles have been equipped with hybrid, diesel-electric drives to improve fuel efficiency and stealth capabilities. These vehicles require an accurate estimate of the power duty cycles during distinct operating conditions. To meet this demand, a GPS-based mobility power and duty cycle analysis is one approach to predict the power requirements of on-road and off-road vehicles. The dynamic vehicle parameters needed to estimate the forces developed during locomotion are determined from the GPS tracking data, and these forces include the following: the motion resistance, gravitational, linear inertia, rotational inertia, and aerodynamic drag. The motion resistance force generated ...


Biarticular Muscles Influence Postural Responses: Implications For Treatment Of Stiff-Knee Gait, Ashley Elizabeth Clark May 2012

Biarticular Muscles Influence Postural Responses: Implications For Treatment Of Stiff-Knee Gait, Ashley Elizabeth Clark

Masters Theses

Stiff knee gait is a prevalent and troublesome movement disorder among children with cerebral palsy, where peak knee flexion is diminished during swing phase. Rectus femoris transfer surgery, a common treatment for stiff-knee gait, reattaches the distal tendon of this biarticular, or two joint, muscle to a new site, such as the sartorius insertion on the tibia. Biarticular muscles play a unique role in motor control. As a biarticular muscle, rectus femoris may offer unrecognized benefits to maintain balance. This study uses musculoskeletal modeling and simulation to investigate the role of this biarticular muscle on balance recovery following support-surface translations ...


Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng May 2012

Test Size And Volume Effects On Fatigue Behavior Of Bulk Metallic Glasses (Bmgs), Qingming Feng

Masters Theses

As a potential structural material, performance of bulk metallic glasses (BMGs) under cyclic loading is critical in applications. Among the mechanical properties of metallic glasses, the fatigue behavior received less attention and is not well understood. BMGs exhibit significant size effects on the mechanical behavior under monotonic loading, such as compression, tension, and bending. At the same time, different test-volume could lead to a distinct difference in the mechanical behavior of BMGs.

The fatigue behavior of the Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 [atomic percent (at. %)] BMG alloy (Vitreloy 105) with ...


Development And Verification Of A Navier-Stokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell May 2012

Development And Verification Of A Navier-Stokes Solver With Vorticity Confinement Using Openfoam, Austin Barrett Kimbrell

Masters Theses

Vorticity Confinement (VC) is a numerical technique which enhances computation of fluid flows by acting as negative diffusion within the limit of vortical regions, preventing the inherent numerical dissipation present with conventional methods. VC shares similarities with large eddy simulation (LES), but its behavior is based on a stable negative dissipation of vortical structures controlled by the automatic balance between two parameters, μ [mu] and ε [epsilon].

In this thesis, three-dimensional, parallel-computing Navier-Stokes solvers with VC are developed using the OpenFOAM computational framework. OpenFOAM is an open-source collection of C++ libraries developed for computational fluid dynamics. Object-oriented programming concepts are ...


Methods Of Optimizing The Gas Exchange Process To Improve Fuel Efficiency Of Small Carbureted Spark Ignition Engines, Cory Hannibal Huck Jan 2012

Methods Of Optimizing The Gas Exchange Process To Improve Fuel Efficiency Of Small Carbureted Spark Ignition Engines, Cory Hannibal Huck

Masters Theses

"Fuel efficiency of internal combustion engines long has been a topic of concern. Much effort has been made to optimize the fuel efficiency of large automotive type engines. However, for small engine manufactures subject to tight cost constraints, this has only recently become an area of great focus. A method by which the fuel efficiency of an engine can be improved is through optimization of the intake process. Specifically, reductions in flow losses and the choice of appropriate valve event timings can provide ways to make gains towards more fuel efficient operation. The challenge arises when the focus is on ...


Force Sensing Of An Asymmetric Dielectric Barrier Discharge Using Mechanical Resonators, Mark Dawson Emanuel Jan 2012

Force Sensing Of An Asymmetric Dielectric Barrier Discharge Using Mechanical Resonators, Mark Dawson Emanuel

Masters Theses

"Dielectric barrier discharge (DBD) plasma actuators are of great interest in flow control research and application. DBD plasma actuators are low-cost, lightweight, high voltage devices that have the capability of generating small amounts of thrust on the order of a few tenths of a gram. The thrust is created by rapidly pulsing plasma discharges which correlate to the frequency of the applied alternating current waveform, in the low kilohertz range.

Plasma actuators experience a reactant force generated by the pulsed plasma charging and then expelling air away from the charged surface. This force fluctuates with time as the plasma is ...


Development Of Kinectᵀᴿ Applications For Assembly Simulation And Ergonomic Analysis, Chinmay Prakash Daphalapurkar Jan 2012

Development Of Kinectᵀᴿ Applications For Assembly Simulation And Ergonomic Analysis, Chinmay Prakash Daphalapurkar

Masters Theses

"Marker-less motion capture technology has been harnessed for several years to track human movements for developing various applications. Recently, with the launch of Microsoft Kinect, researchers have been keenly interested in developing applications using this device. Since Kinect is very inexpensive (only $110 at the time of writing this thesis), it is a low-cost and a promising substitute for the comparatively expensive marker-based motion capture systems. Though it is principally designed for home entertainment, numerous applications can be developed with the capabilities of Kinect. The skeleton data of a human being tracked by a single Kinect device is enough to ...


Process Planning And Control Of Functionally Graded Parts Using Freeze-Form Extrusion Fabrication, Bradley Kenneth Deuser Jan 2012

Process Planning And Control Of Functionally Graded Parts Using Freeze-Form Extrusion Fabrication, Bradley Kenneth Deuser

Masters Theses

"Freeze-form Extrusion Fabrication (FEF) is an additive manufacturing technology that is capable of fabricating complex three-dimensional parts. FEF works by depositing an aqueous-based colloidal ceramic or metal paste in a layer-by-layer fashion below the freezing point of the aqueous medium as to rapidly freeze the paste. The FEF machine in the present study is equipped with three syringes and is capable of mixing each paste in a desired composition ratio by using an inline static mixer. Compensation for the transport delay caused by the static mixer is necessary; therefore, an algorithm was developed to apply a one-dimensional (1D) composition gradient ...


Advanced Moisture Modeling Of Polymer Composites, Nathan Robert Roe Jan 2012

Advanced Moisture Modeling Of Polymer Composites, Nathan Robert Roe

Masters Theses

"Composite materials absorb moisture from the environment and over time this moisture absorption affects the mechanical performance of the material. In order to determine the long-term moisture effects on the component, representative parts must be tested after having been exposed to an accelerated moisture-conditioning environment. This accelerated environment simulates the worst-case exposure conditions that a part might experience. Currently accepted methodologies for analyzing the time required to condition specimens are limited, only allowing simple geometry and an assumption that diffusivity rates are independent of the flow path or direction. Therefore, a more advanced finite element method is desired. In the ...


Pulmonary Fluid Dynamics And Aerosol Drug Delivery In The Upper Tracheobronchial Airways Under Mechanical Ventilation Conditions, Timothy Andrew Van Rhein Jan 2012

Pulmonary Fluid Dynamics And Aerosol Drug Delivery In The Upper Tracheobronchial Airways Under Mechanical Ventilation Conditions, Timothy Andrew Van Rhein

Masters Theses

"The effects of mechanical ventilation conditions on fluid flow and particle deposition were studied in a computer model of the human airways. The frequency with which aerosolized drugs are delivered to mechanically ventilated patients demonstrates the importance of understanding the effects that ventilation parameters have on particle deposition in the human airways. Past studies that modeled particle deposition in silico frequently used an idealized geometry with steady inlet conditions. With recent advancements in computational power and medical imaging capabilities, studies have begun to use more realistic geometries or unsteady inlet conditions that model normal breathing. This study focuses specifically on ...


Development Of A Technique For Testing Of Tensile Properties With Miniature Size Specimens For Metal Additive Manufacturing, Sujitkumar Dongare Jan 2012

Development Of A Technique For Testing Of Tensile Properties With Miniature Size Specimens For Metal Additive Manufacturing, Sujitkumar Dongare

Masters Theses

"The study of mechanical properties of metals provides a basis to decide on the capability of a particular metal for a task and also to make predictions about its life. The concepts of stress, strain and strength of materials are employed in practically every engineering discipline. Mechanical properties such as stiffness, yield strength, tensile strength, ductility, toughness, impact resistance, creep resistance, fatigue resistance and others, influence the design, fabrication and service life of equipment. Therefore, more than one property is considered for the material selection process for an application. For complete understanding of any material and its feasibility for a ...


Investigating The Effects Of Internally Trapped Residuals On The Performance Of A Homogeneous Charge Compression Ignition (Hcci) Engine, Aaron David Attebery Jan 2012

Investigating The Effects Of Internally Trapped Residuals On The Performance Of A Homogeneous Charge Compression Ignition (Hcci) Engine, Aaron David Attebery

Masters Theses

"Homogeneous charge compression ignition (HCCI) combustion introduces great opportunity for decreased emissions along with greater engine efficiencies. Implementing an innovative combustion mode such as HCCI presents a great challenge for the engine research community. One such challenge is controlling the innate cyclic variability from this chemical kinetics controlled auto-ignition event when transitioning to or from a SI operating mode. This work includes the study of cycle-to-cycle dynamics that occur within the partial burn regime of an HCCI engine as it approaches the misfire limit. Within this regime there are many successive incomplete combustion events that will impact the next cycle ...


Design Of A Vortex Induced Vibration Based Marine Hydro-Kinetic Energy System, Varun Michael Lobo Jan 2012

Design Of A Vortex Induced Vibration Based Marine Hydro-Kinetic Energy System, Varun Michael Lobo

Masters Theses

"Hydrokinetic energy harvesting based on vortex induced vibration (VIV) of a bluff body is discussed. VIV is defined as the vibration incurred on a bluff body due to an external fluid flowing over it. These vibrations are the results of boundary layer separation from the surface of the body. An optimized VIV generator has been developed, that utilizes a non-contact type linear magnetic device for generation of energy. The cylinder was chosen such that at the mass ratio (m*) was always lower than the critical mass (m*critical= 0.52). The studies were based on two complementary techniques: (a) computational ...


Height Dependent Laser Metal Deposition Process Modeling, Patrick M. Sammons Jan 2012

Height Dependent Laser Metal Deposition Process Modeling, Patrick M. Sammons

Masters Theses

"Laser Metal Deposition (LMD) is used to construct functional parts in a layer-by-layer fashion. The heat transfer from the melt region to the solid region plays a critical role in the resulting material properties and part geometry. The heat transfer dynamics can change significantly as the layers increase, depending on the geometry of the sub layers. However, this effect is unaccounted for in previous analytical models, which are only valid for a single layer. This thesis develops a layer dependent model of the LMD process for the purpose of designing advanced layer-to-layer controllers. A lumped-parameter model of the melt pool ...


5-Axis Tool Path Generation With Collision Detection For Finish Machining Of Freeform Surfaces, Jomy Francis Jan 2012

5-Axis Tool Path Generation With Collision Detection For Finish Machining Of Freeform Surfaces, Jomy Francis

Masters Theses

"Research in the field of Tool path generation for freeform surfaces has been done intensively in the past. However, the main challenge that still exists is the computational efficiency related to the tool path generation. Tool path generation for freeform surface involves instantaneous calculation of new tool orientations which does not collide with the neighboring surfaces. Since the collision check of tool and neighboring surface is done repetitively at every instant of the tool, the calculations at every instant are to be computationally as easy as possible.

This thesis is composed of one paper. Paper I presents a novel extension ...


Ultrasonic Communications System For Health Monitoring Of Hydrokinetic Turbine Blades, Andrew James Heckman Jan 2012

Ultrasonic Communications System For Health Monitoring Of Hydrokinetic Turbine Blades, Andrew James Heckman

Masters Theses

"A health monitoring approach is investigated for hydrokinetic turbine blade applications. In-service monitoring is critical due to the difficult environment for blade inspection and the cost of inspection downtime. Composite blade designs provide a medium for embedding sensors into the blades for in-situ health monitoring. The major challenge with in-situ health monitoring is transmission of sensor signals from the remote rotating reference frame of the blade to the system monitoring station. In the presented work, a novel system for relaying in-situ blade health measurements in hydrokinetic systems is described and demonstrated. An ultrasonic communication system is used to transmit health ...


A Planning Tool To Predict The Welding Angle In Laser Metal Deposition, Sriram Prabhu Jan 2012

A Planning Tool To Predict The Welding Angle In Laser Metal Deposition, Sriram Prabhu

Masters Theses

"Research in Laser Metal Deposition (LMD) has been done rigorously in the past. However, the main challenge that still exists is the production of complex part geometries having overhang features. Production of such features requires individual tracks with a high aspect ratio and wider bead angle. The use of destructible/ non-destructible support structures involves costly post production operations which increase production cost. Tilting or moving the deposition surface can be useful to create overhangs but are applicable only to special cases. Since such techniques have to be used by the manufacturing community, the techniques need to be simple in calculation ...


Integration Of Multiple Vision Systems And Toolbox Development, Rohit Vijay Bapat Jan 2012

Integration Of Multiple Vision Systems And Toolbox Development, Rohit Vijay Bapat

Masters Theses

"Depending on the required coverage, multiple cameras with different fields of view, positions and orientations can be employed to form a motion tracking system. Correctly and efficiently designing and setting up a multi-camera vision system presents a technical challenge. This thesis describes the development and application of a toolbox that can help the user to design a multi-camera vision system. Using the parameters of cameras, including their positions and orientations, the toolbox can calculate the volume covered by the system and generate its visualization for a given tracking area. The cameras can be repositioned and reoriented using toolbox to generate ...


Enhancing The Aerodynamic Performance Of Stepped Airfoils, Ranganadhan Voona Jan 2012

Enhancing The Aerodynamic Performance Of Stepped Airfoils, Ranganadhan Voona

Masters Theses

"The main objective of this research was to investigate the lift and drag characteristics of a stepped airfoil with backward facing steps; apply active flow control technique to enhance the aerodynamic performance of stepped airfoils and examine the possibility of using such airfoils on Unmanned Aerial Vehicles (UAV's). A step was introduced at mid-chord, with a depth of 50% of the airfoil thickness at mid-chord position extending till the trailing edge of a NACA 4415 airfoil. Computational studies were conducted with the use of passive flow control constituting the activation of step and active flow control with the use ...


Thermal Modeling And Analysis Of Polymer Electrolyte Membrane Open Cathode Fuel Cells, Blanca Ollero Loranca Jan 2012

Thermal Modeling And Analysis Of Polymer Electrolyte Membrane Open Cathode Fuel Cells, Blanca Ollero Loranca

Masters Theses

"In the past decade renewable energies have increasingly become a commodity in everyday life. Because of their high power densities and their application versatility, fuel cells have stood out among other sources of renewable energy. In order to improve this technology as the needs for it increases, thermal modeling is an essential step. Researchers in the past have investigated the effect that temperature has on fuel cells. However, not much work has been done on the thermal dynamics of these devices and no one, to the authors knowledge, has studied the speed of response in thermal changes as a function ...


Control Oriented Thermal Modeling Of Lithium Ion Batteries, Derek Brown Jan 2012

Control Oriented Thermal Modeling Of Lithium Ion Batteries, Derek Brown

Masters Theses

"Lithium ion batteries have been widely used in consumer electronics and are beginning to move to the forefront of the automotive and power grid industries. Lithium ion batteries are desirable in these applications because they are high energy density and high specific energy cells, while remaining inexpensive and lightweight. Safety is a concern in every consumer application; therefore, in order for lithium ion battery use to continue growing, advances in battery management systems are needed. Thermal management of lithium ion batteries is currently a critical issue. Applications are becoming more dependent on active liquid thermal management systems. The development of ...


Fabrication Of Complex Ceramic Parts With Sacrificial Material Using Freeze-Form Extrusion Fabrication, Diego Armando Garcia MontañO Jan 2012

Fabrication Of Complex Ceramic Parts With Sacrificial Material Using Freeze-Form Extrusion Fabrication, Diego Armando Garcia MontañO

Masters Theses

"An additive manufacturing process called Freeze-form Extrusion Fabrication (FEF) was developed in this study to fabricate complex ceramic parts that require the use of sacrificial materials. The aqueous paste of alumina (Al₂O₃) was used as the main material, with solids loadings as high as 50 vol. % and water as the main liquid medium. Methyl cellulose, with a 10 vol. % solids loading and 90 vol. % water content, was used as the sacrificial material. The freeze-form extrusion machine has multiple extruders (extrusion devices) capable of fabricating parts from multiple materials without mixing them. The dynamic process of extruding alumina and methyl cellulose ...


Generic Kinematic Simulation For Verification Of Laser Deposition Tool Paths, Sweta Dhaveji Chakravadhanula Jan 2012

Generic Kinematic Simulation For Verification Of Laser Deposition Tool Paths, Sweta Dhaveji Chakravadhanula

Masters Theses

"The development of 3D visual simulation tool for machine simulation is a key approach in saving time and reducing cost. It is an important step before a manufacturing operation is performed on a part, as a tool to detect collision and validate the operation results. There are several kinds of manufacturing equipment being used and hence there is a need for the development of a generalized method to visually simulate a variety of machines. This paper presents the research conducted on describing machine configuration in a generic format which not only gives useful information, but can also be used as ...


A Three-Dimensional Transient Simulation Of An Electrochemical Magnetohydrodynamics Cell With Micro And Millielectrode: A Unified Reconciliation Of Theory And Experiment, Cajon Gonzales Jan 2012

A Three-Dimensional Transient Simulation Of An Electrochemical Magnetohydrodynamics Cell With Micro And Millielectrode: A Unified Reconciliation Of Theory And Experiment, Cajon Gonzales

Masters Theses

"Even though electrochemically induced magnetohydrodynamic (MHD) convection is a straightforward inexpensive method for moving fluids in confined spaces as for example during electrodeposition, stripping voltammetry, or in microfluidics, efficient quantitative models only recently have begun to appear. This is traced to complex mathematics that have prevented development of analytical expressions, e.g., for mass-transfer limited currents in analogy to the well-known Levich equation for the rotating electrode. Thus, related literature expressions remain mainly phenomenological concerning particular cell geometries or applications. Here, using such reports as points of departure, we validate a computationally rigorous description of the magnetoelectrochemical problem and define ...