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Articles 1351 - 1380 of 1700
Full-Text Articles in Mechanical Engineering
Development Of A Multiple Microphone Probe Calibrator, Jonathan Reed Oldham
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
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, …
Investigation Of Particle Velocity And Drag With Spherical And Non-Spherical Particles Through A Backward Facing Step, Kyle Frederick Larsen
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 …
A Geometry-Based Motion Planner For Direct Machining And Control, Robert M. Cheatham
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.
Autonomic Product Development Process Automation, John E. Daley
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
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
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
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 …
An Investigation Of A Positive Engagement, Continuously Variable Transmission, Brian S. Andersen
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
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 …
Large-Displacement Linear-Motion Compliant Mechanisms, Allen B. Mackay
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
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 …
Panoramic Video For Efficient Ground Surveillance From Small Unmanned Air Vehicles, Joseph Aaron Jackson
Panoramic Video For Efficient Ground Surveillance From Small Unmanned Air Vehicles, Joseph Aaron Jackson
Theses and Dissertations
As unmanned air vehicle (UAV) utilization increases in Wilderness Search and Rescue (WiSAR) efforts, onboard sensors yielding more information will be desired. UAVs can assist WiSAR efforts by accelerating the ground search process through returning quality aerial footage of the terrain. Additionally, tracking the progress of a search by populating a digital map with video resolution data increases confidence that a comprehensive search of the region has been made. This thesis presents methods for acquiring video from multiple video sensors and fusing them into a single rendered video stream as a Virtual Gimbal. The panoramic video stream is the first …
Applications Of Search Theory To Coordinated Searching By Unmanned Aerial Vehicles, Steven R. Hansen
Applications Of Search Theory To Coordinated Searching By Unmanned Aerial Vehicles, Steven R. Hansen
Theses and Dissertations
Concepts in optimal search theory have been used in human-based aerial search since World War II. This thesis addresses the technical and theoretical issues necessary to apply this crucial theory to search path planning for Small Unmanned Aerial Vehicles (SUAVs). A typical search often requires that more than one target be located. Accordingly, a method is presented to locate multiple targets in three dimensions, as well as to differentiate between them. However, significant error can be present when locating targets from an airborne platform, and the idea of target quality is also introduced as a way to describe the reliability …
Optimizing Product Variant Placement To Satisfy Market Demand, Jonathan Roger Parkinson
Optimizing Product Variant Placement To Satisfy Market Demand, Jonathan Roger Parkinson
Theses and Dissertations
Many companies use product families in order to offer product variants that appeal to different market segments while minimizing costs. Because the market demand is generally not uniform for all possible product variants, during the design phase a decision must be made as to which variants will be offered and how many. This thesis presents a new approach to solving this problem. The product is defined in terms of performance parameters. The market demand is captured in a preference model and applied to these parameters in order to represent the total potential market. The number and placement of the product …
Objective Test Methods For Waveguide Audio Synthesis, Steven Gregory Wood
Objective Test Methods For Waveguide Audio Synthesis, Steven Gregory Wood
Theses and Dissertations
Acoustic Physical Modeling has emerged as a newer musical synthesis technique. The most common form of physical modeling synthesis in both industry and academia is digital waveguide synthesis. Commercially available for the past thirteen years, the top synthesizer manufacturers have chosen to include physical modeling synthesis in their top of the line models. In the area of audio quality testing, the most common tests have traditionally been group listening tests. While these tests are subjective and can be expensive and time-consuming, the results are validated by the groups' proper quality standards. Research has been conducted to evaluate objective testing procedures …
An Evaluation Of American Companies That Outsource Manufacturing To China: Decision-Making And Performance, Michael Kenyon Favreau
An Evaluation Of American Companies That Outsource Manufacturing To China: Decision-Making And Performance, Michael Kenyon Favreau
Theses and Dissertations
The topic of outsourcing ranks at the top of business issues for a wide variety of companies (Wery, 2004; Ezrati, 2004). The majority of American companies believe that offshore-related matters rank as the most strategic decisions that management is expected to make in the next 12 months (Wery, 2004). “Outsourcing in China can help many companies save money, but it can be very frustrating if not done right" (Ting, 2004). The perceived benefits of outsourcing production to China are tremendously enticing, but a lack of understanding of the total costs involved lures many companies into outsourcing when it is not …
Particle Size, Gas Temperature, And Impingement Cooling Effects On High Pressure Turbine Deposition In Land Based Gas Turbines From Various Synfuels, Jared M. Crosby
Particle Size, Gas Temperature, And Impingement Cooling Effects On High Pressure Turbine Deposition In Land Based Gas Turbines From Various Synfuels, Jared M. Crosby
Theses and Dissertations
Four series of tests were performed in an accelerated deposition test facility to study the independent effects of particle size, gas temperature, and metal temperature on ash deposits from two candidate power turbine synfuels. The facility matches the gas temperature and velocity of modern first stage high pressure turbine vanes while accelerating the deposition process. This is done by matching the net throughput of particulate out of the combustor with that experienced by a modern power turbine. In the first series of tests, four different size particles were studied by seeding a natural-gas combustor with finely-ground coal ash particulate. The …
Lifetime Testing Of Wire-Grid Polarizers With Selected Over-Coatings, Steven J. Malone
Lifetime Testing Of Wire-Grid Polarizers With Selected Over-Coatings, Steven J. Malone
Theses and Dissertations
Wire-grid polarizers (WGPs) offer superior extinction, durability, angle of incidence, and heat resistance when compared to traditional organic polarizers. WGPs are found in applications such as high lumen lighting, laser devices, high lumen digital cinema projectors, LED packaging, and other integrated optical applications and are driving the need for over-coatings. Over-coating a WGP has been found to increase lifetime and durability. This research provides lifetime data on coated and uncoated WGPs. WGPs over-coated with 100nm of SiO2, 300nm of MgF2, and with no over-coating were heated to temperatures of 450 ºC, 500 ºC, and 550 ºC and timed until they …
An Investigation Of Wear-Resistant Coatings On An A390 Die-Cast Aluminum Substrate, D. Adam Mower
An Investigation Of Wear-Resistant Coatings On An A390 Die-Cast Aluminum Substrate, D. Adam Mower
Theses and Dissertations
In this investigation, four coatings were tested for their ability to increase the wear life of A390 aluminum primary clutch sheaves used in continuously variable transmission (CVT). The coatings tested were: hard chrome, electroless nickel metal, hard coat anodizing and composite ceramic coating. The primary clutch sheave material is a die-cast A390 aluminum. A wear test stand was developed to duplicate wear found on CVTs currently in use. The wear was evaluated using four methods. First, the change in shift characteristics of the CVT while running on the wear test stand, second a change in performance using an ATV and …
Effects Of Spanwise And Discrete Disturbances On Separating Boundary Layers On Low Pressure Turbine Blades, Daniel D. Reimann
Effects Of Spanwise And Discrete Disturbances On Separating Boundary Layers On Low Pressure Turbine Blades, Daniel D. Reimann
Theses and Dissertations
Flow measurements were made on two highly loaded, low pressure turbine blade configurations in a low-speed, linear cascade facility. The L1M blade has a design Zweifel coefficient of 1.34 with a peak cp near 47% cx (mid-loaded) and the Pack B blade has a design Zweifel coefficient of 1.15 with a peak cp at 63% cx (aft-loaded). Flow velocity and surface pressure measurements were taken for Rec=20,000 and 3% inlet freestream turbulence. For these operating conditions, a large separation bubble forms on the blade suction surface, beginning at 59% cx and reattaching at 86% cx on the L1M blade and …
The Effects Of Vortex Generator Jet Frequency, Duty Cycle, And Phase On Separation Bubble Dynamics, Matthew J. Bloxham
The Effects Of Vortex Generator Jet Frequency, Duty Cycle, And Phase On Separation Bubble Dynamics, Matthew J. Bloxham
Theses and Dissertations
Vortex generator jets (VGJs) have proven to be effective in minimizing the separation losses on low-pressure turbine blades at low Reynolds numbers. Experimental data collected using phase-locked particle image velocimetry and substantiated with a hot-film anemometer were used to answer fundamental questions about the influence of VGJs on a separated boundary layer. The data were collected on the suction surface of the Pack B blade profile, which has a non-reattaching separation bubble beginning at 68% axial chord. Two VGJ pulse histories were created with different frequencies, jet durations, and duty cycles. The mechanisms responsible for boundary layer separation control were …
Characterizing The Frictional Interface In Friction Stir Welding, Daryl A. Stratton
Characterizing The Frictional Interface In Friction Stir Welding, Daryl A. Stratton
Theses and Dissertations
Quantitative understanding of frictional phenomena between the tool and the workpiece is essential for accurate modeling of the Friction Stir Welding (FSW) process. Two methods of measuring the tool-workpiece interface are proposed that allow frictional measurements to be made under extreme conditions. The first method uses a cylindrically curved surface in contact with a flat plate. The ranges of temperature, velocity, and normal force used in this method are 100–600°C, 0.38–2.0 m/s (75–400) surface feet per minute (SFM)), and 450–2700 N (100–600 lbf), respectively. Data are gathered at different parameter level combinations to provide enough data to create an empirical …
A Qualitative Study Of Selected Quality Knowledge And Practices In Guangdong Province, China, Tyler R. Thomas
A Qualitative Study Of Selected Quality Knowledge And Practices In Guangdong Province, China, Tyler R. Thomas
Theses and Dissertations
The manufacturing industry has become very competitive in today's global market environment. Many US companies are faced with the choice of keeping their manufacturing domestic or looking to low cost off-shore countries to take advantage of the labor costs differences. To gain an understanding of the state of manufacturing in China, a major focus in the manufacturing world today, this thesis was undertaken. This thesis presents the findings of research conducted in Guangdong Province, China in June - July, 2005. This research addressed customer focus, leadership and general manufacturing and quality knowledge and practices of small, medium and large sized …
Spot Friction Welding Of Ultra High-Strength Automotive Sheet Steel, Jack H. Sederstrom
Spot Friction Welding Of Ultra High-Strength Automotive Sheet Steel, Jack H. Sederstrom
Theses and Dissertations
Spot friction welding (SFW) was performed on ultra high strength steel (UHSS) steel sheet commonly used in automobile manufacturing. Alloys studied included DP780, DP780EG, DP980, and DF140T sheet steel of varying thickness from 1.2 mm to 1.4 mm. Welding was accomplished using a PCBN standard tool. Weld strengths were then compared to a proposed AWS standard. Initial hardness readings were taken in cross sectioned samples. Grain structure in a SFW is presented. Resistance spot welds were created in three steels. This study focuses on the strength of SFW joints as compared to traditional resistance spot welding (RSW) in welding like …
Development Of An Efficient Solar Powered Unmanned Aerial Vehicle With An Onboard Solar Tracker, Troy Dixon Tegeder
Development Of An Efficient Solar Powered Unmanned Aerial Vehicle With An Onboard Solar Tracker, Troy Dixon Tegeder
Theses and Dissertations
Methods were developed for the design of a solar powered UAV capable of tracking the sun to achieve maximum solar energy capture. A single-axis solar tracking system was designed and constructed. This system autonomously rotated an onboard solar panel to find the angle of maximum solar irradiance while the UAV was airborne. A microcontroller was programmed and implemented to control the solar tracking system. A solar panel and an efficient airframe capable of housing the solar tracking system was designed and constructed. Each of these subsystems was tested individually with either ground or flight tests. Ultimately, the final assembled system …
Design, Construction, And Validation Of The Afit Small Scale Combustion Facility And Section Model Of The Ultra-Compact Combustor, Wesley S. Anderson
Design, Construction, And Validation Of The Afit Small Scale Combustion Facility And Section Model Of The Ultra-Compact Combustor, Wesley S. Anderson
Theses and Dissertations
The AFIT small-scale combustion facility is complete and its first experiment designed and built. Beginning with the partially built facility, detailed designs have been developed to complete the laboratory in order to run small-scale combustion experiments at atmospheric pressure. A sectional model of the Ultra-Compact Combustor has also been designed and built. Although the lab's specific design intent was to study the UCC's cavity-vane interaction, facility flexibility has also been maintained for future work. The design enabled the completion of liquid fuel and air delivery systems, power and control systems, and test equipment. The design includes failsafe operation, remote control, …
Evaluating The Application Of Modularity To Reduce Market Risk In Technology Push Products, Aaron John Hopkinson
Evaluating The Application Of Modularity To Reduce Market Risk In Technology Push Products, Aaron John Hopkinson
Theses and Dissertations
Technology push product development presents a number of challenges over the more typical market pull product development. Despite these challenges, enough advantages exist to motivate firms to develop technology push products at greater risk. Modularity is a tool that can address some of these challenges. Currently most research and application of modularity have focused on market pull product development efforts. The research in this thesis explores the value of modularity in technology push product development through the development of methods and the analysis of 68 example products including 35 technology push products. A method has been developed for quantifying the …
Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard
Characterizationn Of Polumer-Based Mems Pyroelectic Infrared Detector, Mark E. Allard
Theses and Dissertations
AFRL/MLPJE had developed a novel thermal sensing material termed protein-impregnated-polymer (PIP). Thus far, a proof-of-concept has been demonstrated using a macro-sized pixel (0.64 mm2) as a bolometric detector. In an effort to better characterize this novel thermal sensing material, experimental data was used to determine figures of merit (FOMs) comparative to off-the-shelf thermal detectors. Microelectromechanical (MEMS) pixels were designed and used as the support structure for an inkjet-deposited droplet of the PIP. During the material characterization, two observations were made: PIP is a pyroelectric material, and the polymer (polyvinyl alcohol (PVA)) without the protein was found to be …
Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham
Characterization Of Intercalated Graphite Fibers For Microelectromechanical Systems (Mems) Applications, Bryan W. Winningham
Theses and Dissertations
Research was accomplished to characterize the electrical and physical characteristic changes of the Thornel® P-100 carbon fiber and five variants when intercalated with 96% sulfuric acid and incorporated the use of Microelectromechanical Systems (MEMS) structures for testing purposes. The five fiber variants were oxidized in 1 M nitric acid at 0.5 A for 30 seconds, 1 and 2 minutes, the last two samples were detreated at 1150 °C for one hour prior to the nitric acid treatment. The fibers were mounted onto a MEMS die, placed into a chip carrier, sulfuric acid added, the chip carrier sealed and testing accomplished. …