Mechanical Engineering Commons^™

Intrustive Probe Measurements In A High-Temperature Mach Two Flow, Sonya Renee Nelson

Masters Theses

To acquire heat transfer measurements of a high temperature Mach two flow a water-cooled calorimeter was placed in the flow and the water temperature rise was used to calculate the heat transfer rate and the recovery temperature of the gas. In addition, a graphite rod with a stainless steel tube at its core was used to measure the total pressure of the flow. This pressure probe was swept through the flow for two test runs to acquire a stagnation pressure profile of the gas flow. All results were compared to NASA CEA computer simulation code results. The heat transfer and …

Influence Of The Sampling Procedure On Extracted Jet Engine Exhaust Gas Emission Samples, Ashley Dawn Owens

Masters Theses

The purpose of this thesis is to analyze the effects of an intrusive sample extraction process on the thermo-chemistry of extracted gas samples taken from exhaust of a GE-J85-H turbojet engine. The engine testing took place at University of Tennessee Space Institute in Tullahoma, TN, where the J85 was installed in a test bay of a research facility. The results of the analysis validate that testing methods used had a low probability of disturbing the exhaust chemistry. The tools used to analyze the thermal history of the extracted samples were the NASA CEA and LSENS programs. Several different cases of …

Effect Of Length On The Performance Of Lean NoX Traps, Vitaly Y. Prikhodko

Masters Theses

The effect of monolith length on the NO_x performance of two different Lean NO_x Traps has been investigated using a bench flow reactor (BFR). The washcoat composition of one of the catalysts consists of Pt/K/γ-Al₂O₃; the major components of the other catalyst include Pt, Pd, Rh, barium, ceria and zirconia supported on γ-alumina washcoat. Samples of 2.22-cm in diameter and length of 2.54, 5.08 and 7.62-cm within each LNT were evaluated with long and short-cycle experiments at a fixed gas hourly space velocity, and results were compared between samples of different lengths. No significant …

Development Of A Multiple Microphone Probe Calibrator, Jonathan Reed Oldham

Theses and Dissertations

This paper presents the theory, design, and validation of a microphone calibrator used to calibrate multiple microphones simultaneously. This work was done in conjunction with the development of an acoustic energy density probe, which was used to validate the calibrator. The probe uses multiple microphones to acquire the data needed to compute the acoustic energy density. The probe microphones are 0.006 m diameter electret microphones which typically do not have an ideal “flat" response over a wide range of frequencies as compared to precision condenser microphones. The probe microphone characteristics prompted the need for simultaneous, multi-microphone magnitude calibration. The idea …

Elliptical Rolling Link Toggle Mechanisms For Passive Force Closures With Self-Adjustment, Jacob Ross Montierth

Theses and Dissertations

This thesis presents elliptical rolling contact joints as an alternative to circular rolling contact and conventional revolute joints where high quality force transmission "low friction and backlash" with variable output are desired. Parameters specific to the joint and its position are developed in terms of relative link angles and elliptical surface geometry. These parameters are used to generate the basic forward kinematics for elliptical rolling link toggle mechanisms with oscillatory motion and high mechanical advantage. As large compressive loads are characteristic of such mechanisms, stress conditions are identified and principles for joint stability with variable, precision outputs are discussed. Finally, …

A Geometry-Based Motion Planner For Direct Machining And Control, Robert M. Cheatham

Theses and Dissertations

Direct Machining And Control (DMAC) is a new method of controlling machine tools directly from process planning software. A motion planning module is developed for the DMAC system that operates directly off path geometry without pre-tessellation. The motion planner is developed with the intent to process Bezier curves. The motion planning module includes a deterministic predictor-corrector-type curve interpolator, a dynamics limiting module, and a two-pass jerk-limited speed profiling algorithm. The methods are verified by machining an automotive surface in a clay medium and evaluating the resultant machine dynamics, feed rate, and chordal error throughout the machining process.

Investigation Of Particle Velocity And Drag With Spherical And Non-Spherical Particles Through A Backward Facing Step, Kyle Frederick Larsen

Theses and Dissertations

Numerous practical applications exist where dispersed solid particles are transported within a turbulent accelerating or decelerating gaseous flow. The large density variation between phases creates the potential for significant differences in velocity known as velocity slip. Flow over a backward facing step provides a well characterized, turbulent, decelerating flow useful for measuring the relative velocities of the solid and gaseous phases in order to determine velocity slip and particle drag. Numerous investigations have been conducted to determine the gas phase velocity in a backward facing step for both laminar and turbulent flows and therefore the gas phase flow is well …

Autonomic Product Development Process Automation, John E. Daley

Theses and Dissertations

Market globalization and mass customization requirements are forcing companies towards automation of their product development processes. Many task-specific software solutions provide localized automation. Coordinating these local solutions to automate higher-level processes requires significant software maintenance costs due to the incompatibility of the software tools and the dynamic nature of the product development environment. Current automation methods do not provide the required level of flexibility to operate in this dynamic environment. An autonomic product development process automation strategy is proposed in order to provide a flexible, standardized approach to product development process automation and to significantly reduce the software maintenance costs …

Comparing The Feasibility Of Cutting Thin-Walled Sections From Five Commonly Used Metals Utilizing Wire Electric Discharge Machining, Richard C. Stephenson

Theses and Dissertations

Wire Electric Discharge Machining (wire-EDM) is a non-traditional machining process. Controlled electric sparks are successively used to vaporize part of a workpiece along a programmed path in order to machine a desired part. Because there is no tool that comes in direct contact with the workpiece, it is possible to machine thin, delicate parts. This thesis was designed to observe and analyze the differences in cutting capabilities for a conventional wire-EDM machine when cutting thin-walled sections from five commonly used metals utilizing a variation of roughing and finishing passes. The five metals that were used in this study are: Aluminum …

Development Of Deployable Wings For Small Unmanned Aerial Vehicles Using Compliant Mechanisms, Steven D. Landon

Theses and Dissertations

Unmanned Air Vehicles (UAVs) have recently gained attention due to their increased ability to perform sophisticated missions with less cost and/or risk than their manned counterparts. This thesis develops approaches to the use of compliant mechanisms in the design of deployable wings for small UAVs. Although deployable wings with rigid-link mechanisms have been used in the past to maintain flight endurance while minimizing required storage volume, compliant mechanisms offer many advantages in manufacturability and potential space savings due to function sharing of components. A number of compliant, deployable wing concepts are generated and a classification system for them is formed. …

Friction Stir Welding Of High-Strength Automotive Steel, Eric Michael Olsen

Theses and Dissertations

The following thesis is a study on the ability to create acceptable welds in thin-plate, ultra-high-strength steels (UHSS) by way of friction stir welding (FSW). Steels are welded together to create tailor-welded blanks (TWB) for use in the automotive industry. Dual Phase (DP) 590, 780, and 980 steel as well as Transformation-Induced Plasticity (TRIP) 590 steel with thicknesses ranging from 1.2 mm to 1.8 mm were welded using friction stir welding under a variety of processing conditions, including experiments with dissimilar thicknesses. Samples were tested under tensile loads for initial determination if an acceptable weld had been created. Acceptable welds …

Modelamiento, Diseño Y Automatización De Un Modelo Genérico De Secador De Polen, Erika Johana Ibarra Erazo, Julio Enrique Fernandez Gutierrez

Ingeniería en Automatización

No abstract provided.

A Finite Difference Method For Studying Thermal Deformation In A Three-Dimensional Microsphere Exposed To Ultrashort-Pulsed Lasers, Xudong Du

Doctoral Dissertations

Ultrashort-pulsed lasers with pulse durations on the order of sub-picoseconds to femtoseconds possess the capabilities in limiting the undesirable spread of the thermal process zone in a heated sample which have been attracting worldwide interest in science and engineering. Success of ultrashort-pulsed lasers in real application relies on: (1) well characterized pulse width, intensity and experimental techniques; (2) reliable microscale heat transfer models; and (3) prevention of thermal damage. Laser damage by ultrashort-pulsed lasers occurs after the heating pulse is over since the pulse duration time is extremely short and the heat flux is essentially limited to the region within …

An Intermediate-Layer Lithography Method For Producing Metal Micron/Nano Patterns And Conducting Polymer-Based Microdevices, Xinchuan Liu

Doctoral Dissertations

Metals have been widely used in the areas of integration circuit (IC) and microelectromechanical systems (MEMS) fields as materials for gates, contact pads, interconnects, corrosion resistance coatings, rectifying contacts, redundancy memories, heating elements, mechanical parts, magnetic component, etc. due to their good properties, such as high electrical conductivity and good thermal conductivity. Conducting polymers, because of their promising potential to replace silicon and metals in building devices, have attracted great attention in recent decades.

Traditional photolithography methods are often used to pattern metals and conducting polymers. However, it cannot be used to fabricate nano patterns because the minimum feature size …

Shaken Baby Syndrome: Retinal Hemorrhaging. A Biomechanical Approach To Understanding The Mechanism Of Causation, Steven Alex Hans

Mechanical & Aerospace Engineering Theses & Dissertations

Shaken Baby Syndrome (SBS) is a form of abuse where typically an infant, age six months or less, is held and shaken. There may or may not be direct impact associated with this action. Further, there is very little agreement on the actual mechanism of SBS. Clinical studies are limited in showing the exact mechanism of injury and only offer postulations and qualitative descriptions. SBS has received much attention in the media, has resulted in a great deal of litigation and can be the source of unfounded accusations. Therefore, it is necessary to try to quantify the forces that may …

An Investigation Of A Positive Engagement, Continuously Variable Transmission, Brian S. Andersen

Theses and Dissertations

A continuously variable transmission (CVT) is a type of transmission that allows an infinitely variable ratio change within a finite range, allowing the engine to continuously operate in an efficient or high performance range. A brief history of CVTs is presented, including the families under which they can be categorized. A new family of CVTs, with the classification of positive engagement, is presented. Three different published embodiments of CVTs of the positive engagement type are presented describing a meshing problem that exists apparently regardless of the embodiment in this family. The problem is called the non-integer tooth problem and its …

Computationally Efficient Modeling Of Transient Radiation In A Purely Scattering Foam Layer, Rudolph Scott Larson

Theses and Dissertations

An efficient solution method for evaluating radiative transport in a foam layer is a valuable tool for predicting the properties of the layer. Two different solution methods have been investigated. First, a reverse Monte Carlo (RMC) simulation has been developed. In the RMC simulation photon bundles are traced backwards from a detector to the source where they were emitted. The RMC method takes advantage of time reflection symmetry, allowing the photons to be traced backwards in the same manner they are tracked in a standard forward Monte Carlo scheme. Second, a reduced order model based on the singular value decomposition …

Development And Evaluation Of A Simulation System Based Upon Standard Pedestrian Thoroughfare Methodologies, Charles O. Pringle

All Master's Theses

This study was undertaken to determine whether existing simulation and modeling systems could be used to analyze and model pedestrian traffic flows. The study incorporates the Highway Capacity Manual 2000 (HCM) (Transportation Research Board, National Research Council [TRB], 2000a) methodologies into a ProModel simulation and then compares and contrasts the results of the HCM calculations with the ProModel simulation.

The Effect Of Cold Work On The Mechanical Behavior Of Niti Shape Memory Alloys, Mohamed Elwi Mitwally

Archived Theses and Dissertations

No abstract provided.

Vibration- Based Damage Detection Using Damage Location Vectors, Khaled Faizallah Mostafa

Archived Theses and Dissertations

No abstract provided.

Direct Simulations Of Cells Motions And Deformations In Flow, Quan Jin

Dissertations

Direct numerical simulations (DNS) are used to study the motions and deformations of blood cells, especially leukocytes, in pressure driven flows in parallel plate channels with both smooth and uneven walls under adhesion force between the leukocytes and the channel wall.

Leukocytes are represented by two composite fluid models. The first model is the compound-drop model in which the cytoplasm and the nucleus are modeled as fluids, and the second one is the drop-rigid-particle model in which the cytoplasm is modeled as a fluid and the nucleus as a rigid particle. The adhesion force is computed using two adhesion force …

Synthesis And Analysis Of Reactive Nanocomposites Prepared By Arrested Reactive Milling, Swati M. Umbrajkar

Dissertations

Different types of reactive nanocomposites have been synthesized by Arrested Reactive Milling (ARM). The technical approach was to increase the interface area available for heterogeneous reaction between solid fuel and oxidizer components. Using aluminum as the main fuel and different metal oxides as oxidizers, highly energetic reactive nanocomposites with different degrees of structural refinement were synthesized. Specifically, stoichiometric Al-MoO₃, Al-CuO, and Al-NaNO₃ material systems were studied in detail.

The correlation of heterogeneous exothermic reactions occurring in the nanocomposite powders upon their heating at low rates and ignition events observed for the same powders heated rapidly was of …

Large-Displacement Linear-Motion Compliant Mechanisms, Allen B. Mackay

Theses and Dissertations

Linear-motion compliant mechanisms have generally been developed for small displacement applications. The objective of the thesis is to provide a basis for improved large-displacement linear-motion compliant mechanisms (LLCMs). One of the challenges in developing large-displacement compliant mechanisms is the apparent performance tradeoff between displacement and off-axis stiffness. In order to facilitate the evaluation, comparison, and optimization of the performance of LLCMs, this work formulates and presents a set of metrics that evaluates displacement and off-axis stiffness. The metrics are non-dimensionalized and consist of the relevant characteristics that describe mechanism displacement, off-axis stiffness, actuation force, and size. Displacement is normalized by …

Multi-Stable Compliant Rolling-Contact Elements, Peter Andrew Halverson

Theses and Dissertations

The purpose of this research is the development of design concepts and models of large-angle, compliant, multistable, revolute joints. This research presents evidence of the capability of these models and concepts by presenting a case study in which the miniaturization of revolute joints are examined. Previous attempts at multistable revolute joints can be categorized into two categories: compliant and non-compliant mechanisms. Non-compliant multistable revolute joints are typified by a combination of pin-in-slot joints, springs, and detents. Due to factors inherit in design, noncompliant joints often succumb to friction, wear, and undesirable motion, that leads to a decline in performance. Compliant …

Analysis And Optimization Of Partial Length, Constrained Damping Layers, Shing-Jia Tang

Doctoral Dissertations

A laminated beam with constrained damping layers is analyzed. The normal strain in the longitudinal direction and shear strain in the viscoelastic layer is considered. Hamilton’s principle is used to derive equations of motion and boundary conditions. A 6th order equation is used to describe the portion of the beam covered with a constrained damping layer and a 4th order equation is used to describe the remainder of the beam. The characteristic equations are solved numerically with a gradient-based optimization method in order to determine normalized loss factor values. The loss parameter (normalized loss factor) is shown to be a …

Modeling Coordinate Measuring Machine Scanning Operations, Pamela Murray Moor

Doctoral Dissertations

International standards require that dimensional inspection operations include an assessment of measurement uncertainty. Scanning coordinate measuring machines (CMMs) are frequently used to measure part surfaces and features, and there is a continuing need to improve their performance for high precision measurement applications. This research provides a mechanism for minimizing the uncertainty of measurements made with a CMM in scanning mode by developing a model of CMM scanning that allows selection of optimum scanning parameters.

The method for selecting scanning parameters is based on models developed from measurements of a ring with a constant five micrometer amplitude swept sine wave machined …

Atomic Force Microscope Imaging Of Dna And Multi Walled Carbon Nanotubes, Jacob Hohnbaum

Mechanical Engineering Undergraduate Honors Theses

The Micro and Nano System Laboratory at the University of Arkansas currently is equipped with an Atomic Force Microscope (AFM). This device can be used to measure objects with resolution on the nanometer scale, but there are a number of technical difficulties in performing scans of carbon nanotubes and DNA. The goal of this research is to successfully perform scans on both carbon nanotubes and DNA and to also establish laboratory processing protocols to re-perform such scans in the future. Previous works performed by other researchers in the laboratory provided basic protocols with which to begin the present research. These …

Mathematical Modeling Of Reverse Flow Oxidation Catalysts, Barath Raghavan

Masters Theses

A theoretical model and a computer simulation on methane (CH4) reduction in a simulated natural gas exhaust mixture are performed for a Reverse-Flow Oxidation Catalyst. This theoretical model is to predict the conversion of methane flowing through an oxidation catalyst with periodic reversal of flow direction. The model developed for this purpose is a transient, 1-Dimensional plug flow model with gas phase reactions and surface reactions. The derivation of the model resulted in the mole balance equation and the energy balance equation for the gas phase and the solid phase. The momentum equation for this model is neglected as it …

Energy Harvesting From Vibration Of A Bridge, Sri Harish Valluru

Masters Theses

Basic research in smart materials and structural systems has demonstrated great potential for enhancing the functionality, serviceability and durability of civil and mechanical infrastructure systems. These smart materials (like piezoelectric materials) can be used as mechanisms to transfer mechanical energy, usually ambient vibration, into electrical energy that can be stored and used to power other devices. The intelligent renewal of aging and deteriorating civil and mechanical infrastructure systems includes efficient and innovative use of high performance sensors, actuators, and structural systems. In this work, a computational model is developed to generate power from the ambient vibration of a single span …

Energy Harvesting Using Optimized Piezoelectric Microcantilevers, Ahmed Mohamed Elalfy

Masters Theses

In this thesis, the energy producing capabilities and efficiency of Piezoelectric materials for ambient energy harvesting from multi-layered micro-cantilevers are analyzed. The cantilevers are then optimized utilizing a homogenization approach involving the redistribution of materials in all regions throughout the three dimensional model to yield the greatest voltage output for a specified tip force under static loading; This would be analogous to having the greatest energy production. The design of the model using the Finite Element Analysis (FEA) software ABAQUS is used in conjunction with a commercial FORTRAN optimization code, where the FEA software handles the mechanical design aspect of …