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Articles 1 - 30 of 38
Full-Text Articles in Mechanical Engineering
Skin-Stiffener Separation In Buckled Composite Plates And Shallow Shells, Mark Edward Robeson
Skin-Stiffener Separation In Buckled Composite Plates And Shallow Shells, Mark Edward Robeson
Mechanical & Aerospace Engineering Theses & Dissertations
The development of an approximate analysis for predicting stresses in the skin-stiffener interface region of composite plates and shallow shells is presented. The analysis determines interlaminar normal stress and transverse shear stresses in the direction of the stiffener axial coordinate and the direction of the inplane coordinate perpendicular to the stiffener axis. The analysis accounts for skin-stiffener interfaces with nonzero thickness and for curvature in the skin and stiffener. The interlaminar normal stress and transverse shear stresses at the interface are applied to the lower face of the skin and the upper face of the stiffener flange as unknown functions, …
Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu
Electro-Mechanical Fatigue Behavior Of A Quasi-Isotropic Laminate With An Embedded Piezoelectric Actuator, Tse Lin Hsu
Theses and Dissertations
This study primarily investigated the electro-mechanical fatigue behavior of the embedded piezoelectric actuators in graphite/epoxy laminate with a lay-up of 0 | ± 45 | 90s. A secondary focus was the investigation of the mechanical fatigue effects of the 0 | 0 | ± 45 | 0 | 0 | 90s laminate with embedded PZT under tensile loading. All the fatigue tests were conducted with a triangular loading waveform which had a frequency of 10 Hz and with R=0. 1. In the electro-mechanical testing, the embedded actuator was excited by a -10 V to -100 V or a 10 V …
Tools For The Design Of Flexible Manufacturind Systems, Prashant A. Patel
Tools For The Design Of Flexible Manufacturind Systems, Prashant A. Patel
Theses
Flexibility in manufacturing systems can broaden the horizons for a company. But the means for achieving it are far more critical. This trend is created by the increase in competitiveness, growth of technology along with demand variations, more customization, and short product life cycles. But "Flexible Manufacturing Systems" to most of the manufacturers sounds like a synonym for automation.
A real Flexible Manufacturing System is designed when every unit of the company is synchronized in such a way to respond in a harmony to any changes that come against it. Fine-tuning of each and every part of the company is …
Object Oriented 3d Dynamic Simulation Of Flow Of Material Through Hopper, Krishnendu Roy
Object Oriented 3d Dynamic Simulation Of Flow Of Material Through Hopper, Krishnendu Roy
Theses
Development of object oriented 3D dynamic simulation of the particle is considered. This code is based on the soft sphere model dealing with both normal force , tangential force and the friction. The development of such a model and the code is motivated by the need to understand the flow patterns of granular material. The prime effort while developing this code was focused on the data encapsulation and secured access to all the attributes of all physical parameters of the bulk solid, which might be endangered by the random access of the interface of the software. A dynamically bound array …
Development And Realization Of A Single-Mode Optical Fiber Ferrule Mold Insert With Twelve Channels, Hsiharng William Yang
Development And Realization Of A Single-Mode Optical Fiber Ferrule Mold Insert With Twelve Channels, Hsiharng William Yang
Doctoral Dissertations
A manufacturing process for an optical fiber ferrule mold insert with twelve channels has been established. This research project presents mask design, mask fabrication, deep X-ray lithography exposure, resist developing, nickel electroforming, as well as surface finishing to attain the final result. Deep X-ray mask fabrication methods are explored, including mechanically machined masks, micro-EDM masks, and E-beam written masks. The exposures to pattern resists and electroforming to fabricate nickel molds up to 500 $\mu$m thickness are reported in this study. Nickel structures for the optical fiber ferrule insert with twelve channels made by electroforming are the final products. A practical …
The Optimized Electrostatic Motor, Christopher Lee Rambin
The Optimized Electrostatic Motor, Christopher Lee Rambin
Doctoral Dissertations
The most common means of electrically activated actuation is the electromagnetic motor. All electromagnetic motors have a low output to weight ratio and low energy efficiency. The motor's weight is due to the coils and magnets used to generate propulsion. The energy loss is mainly the result of Joule heating that is inherent with any current driven device. An electrostatic motor offers the potential of significantly less weight and higher energy efficiency. This lower weight characteristic is due to the epoxide material used to construct the major components of its propulsion unit. Greater efficiency results from the reduced Joule heating …
The Solution Of Hypersingular Integral Equations With Applications In Acoustics And Fracture Mechanics, Richard S. St. John
The Solution Of Hypersingular Integral Equations With Applications In Acoustics And Fracture Mechanics, Richard S. St. John
Mathematics & Statistics Theses & Dissertations
The numerical solution of two classes of hypersingular integral equations is addressed. Both classes are integral equations of the first kind, and are hypersingular due to a kernel containing a Hadamard singularity. The convergence of a Galerkin method and a collocation method is discussed and computationally efficient algorithms are developed for each class of hypersingular integral equation.
Interest in these classes of hypersingular integral equations is due to their occurrence in many physical applications. In particular, investigations into the scattering of acoustic waves by moving objects and the study of dynamic Griffith crack problems has necessitated a computationally efficient technique …
Vortex Wake And Exhaust Plume Interaction, Including Ground Effect, Ihab Gaber Adam
Vortex Wake And Exhaust Plume Interaction, Including Ground Effect, Ihab Gaber Adam
Mechanical & Aerospace Engineering Theses & Dissertations
Computational modeling and studies of the near-field wake-vortex turbulent flows, far-field turbulent wake-vortex/exhaust-plume interaction for subsonic and High Speed Civil Transport (HSCT) airplane, and wake-vortex/exhaust-plume interaction with the ground are carried out. The three-dimensional, compressible Reynolds-Averaged Navier-Stokes (RANS) equations are solved using the implicit, upwind, Roe-flux-differencing, finite-volume scheme. The turbulence models of Baldwin and Lomax, one-equation model of Spalart and Allmaras and two-equation shear stress transport model of Menter are implemented with the RANS solver for turbulent-flow modeling.
For the near-field study, computations are carried out on a fine grid for a rectangular wing with a NACA-0012 airfoil section and …
Analytical And Experimental Study Of Investment Casting With Laser Stereolithography Models, Wen-Long Yao
Analytical And Experimental Study Of Investment Casting With Laser Stereolithography Models, Wen-Long Yao
Dissertations
This dissertation presents an analytical and experimental investigation of ceramic shell cracking during the burnout process in investment casting with internally webbed laser stereolithography (SLA) patterns. Included in the consideration are the cracking temperature of the ceramic shell, the web link buckling temperature, and the glass transition temperature of the epoxy resin. The hypothesis is that shell cracking will occur when the cracking temperature is lower than the glass transition temperature and the web buckling temperature.
An analytical and experimental study has been conducted, with the cross-sectional area, the span length of the web structure, and the shell thickness being …
Automobile Air Bag Inflation System Using Pressurized Carbon Dioxide, Bart Adams
Automobile Air Bag Inflation System Using Pressurized Carbon Dioxide, Bart Adams
Dissertations
A novel air bag inflator based on the evaporation ofliquefied carbon dioxide was developed. A detailed qualitative model wasestablished on the basis of an extensive experimental study. An integratedquantitative model of this inflator was constructed.
The system was studied by discharging the inflatorinto a tank and measuring pressure and temperature evolution (0-50 ms). Thedispersion of the two-phase spray duringinflation was investigated by high-speed cinematography.
The optimal storage pressure of the liquid CO2was found to be 2000 psig (at 22 °C). Two distinct inflator behaviors wereidentified. First, at conditions corresponding to an initial entropy below the critical point, atwo-phase …
Robust Fuzzyclustering For Object Recognition And Classification Of Relational Data, Sumit Sen
Robust Fuzzyclustering For Object Recognition And Classification Of Relational Data, Sumit Sen
Dissertations
Prototype based fuzzy clustering algorithms have unique ability to partition the data while detecting multiple clusters simultaneously. However since real data is often contaminated with noise, the clustering methods need to be made robust to be useful in practice. This dissertation focuses on robust detection of multiple clusters from noisy range images for object recognition. Dave's noise clustering (NC) method has been shown to make prototype-based fuzzy clustering techniques robust. In this work, NC is generalized and the new NC membership is shown to be a product of fuzzy c-means (FCM) membership and robust M-estimator weight (or possibilistic membership). Thus …
Design Of An Effective And Timely Product Development Process For Medical Devices, Jean Benoit Almonor
Design Of An Effective And Timely Product Development Process For Medical Devices, Jean Benoit Almonor
Theses
Effective product development process is one of the most critical issues facing medical devices manufacturing today. There is a need to search for ways to improve or solve the cross organization and company boundaries to enhance the faster release of new medical products to the market. This thesis presents an integrated set of perspectives on the process of new product development of medical devices with dual goals of achieving marketing speed and meet customer satisfaction.
The Attribute Driven Specifications approach described in this thesis, is one of the most valuable tools in the approach to effective product development in medical …
Demanufacturing Metrics For Industrial Fasteners And Disassembly Process, Narendra P. Raj
Demanufacturing Metrics For Industrial Fasteners And Disassembly Process, Narendra P. Raj
Theses
As the society progresses towards ecological maturity, the issue of reducing the environmental burden imposed by used products becomes increasingly important Environmental issues are becoming increasingly relevant for product designers and manufacturers. Public awareness of the value and fragility of an intact ecology is constantly growing, and the traditional assumption that the cost of ecological burdens to be shared by a society, as a whole is no longer accepted. Environmental protection legislation requiring manufacturers to "take back" and recycle used products will be a commonplace throughout Europe and the U.S. in the near future.
Demanufacturing involves separating and disassembling a …
The Experimental Analysis Of Aqueous Lithium Bromide Vertical Film Absorption, William A. Miller
The Experimental Analysis Of Aqueous Lithium Bromide Vertical Film Absorption, William A. Miller
Doctoral Dissertations
A heat and mass transfer test stand was fabricated and used to investigate nonisothermal falling film absorption of water vapor into a solution of aqueous lithium bromide. The absorber was made of borosilicate glass for visual inspection of the falling film. Experiments were conducted on an internally cooled smooth tube of about 0.019 m outside diameter and of 1.53 m length. Laboratory testing evaluated the tube's performance at varying falling film flow rates, pressures, temperatures, and concentrations. No heat and mass transfer additive was used during testing nor had it been previously added to the stand.
The coolant temperature profile …
Design Of The Guidance, Navigation, And Control Subsystem For The Proposed Firebird Spacecraft, Erin Robinson
Design Of The Guidance, Navigation, And Control Subsystem For The Proposed Firebird Spacecraft, Erin Robinson
All Graduate Theses and Dissertations, Spring 1920 to Summer 2023
The Firebird spacecraft is a space mission to gather scientific and physical data on the effects of atmospheric deceleration, commonly called aerobraking. The objective of the Firebird mission is to measure specified aerobraking parameters over a range of reentry velocities to provide a database sufficient to construct and validate mathematical models of such aerobraking mission maneuvers. The Firebird senior design team designed the first spacecraft in the mission series to look at aerobraking at an altitude of 160 kilometers above the surface of the Earth. This paper looks specifically at the design of the subsystem that provides the guidance, navigation, …
Remote Freedom, Dominic M. Florin
Remote Freedom, Dominic M. Florin
Undergraduate Honors Capstone Projects
Increasing mobility is a key to ensuring that a disabled child feels accepted and as normal as possible. The object of Remote Freedom is to provide an inexpensive design that will modify a toy vehicle so that it can run remotely. The case that we designed for was a child with cerebral palsy. Originally the toy vehicle on the market needed major modifications both for the safety of the child and the addition of the remote control The main components that were added were a safety harness, a roll bar and motors to control steering and speed.
It was discovered …
Dual Adaptive Recumbent Trike, Jason V. Eastman
Dual Adaptive Recumbent Trike, Jason V. Eastman
Undergraduate Honors Capstone Projects
The DART team's objective was to develop a tandem recumbent tricycle that would be economical, easy to build, and adaptable. This would involve designing, building and testing the tricycle.
Research And Design Of A High L/D Aircraft, Blake Ashby, Gregory Nielson
Research And Design Of A High L/D Aircraft, Blake Ashby, Gregory Nielson
Undergraduate Honors Capstone Projects
This senior design team, consisting of Blake Ashby, Shelly Barlow, Greg Nielson, Deryl Snyder, and Chris Wright, designed, built, and flew an airplane that met the requirements of the Cessna/ONR Student Design/Build/Fly Competition sponsored by AIAA. This radio-controlled airplane was designed to fly the most laps around a course in seven minutes using only 2.5 pounds of NiCad batteries. A total of three senior design teams from Utah State University designed separate airplanes. Though all three teams designed, built, and tested complete airplanes, each emphasized a different aspect of a successful entry. This team emphasized theoretical and numerical analysis in …
Thin-Layer Prestressed Composite Ferroelectric Driver And Sensor Characterization With Application To Separation Flow Control, Karla M. Mossi
Thin-Layer Prestressed Composite Ferroelectric Driver And Sensor Characterization With Application To Separation Flow Control, Karla M. Mossi
Mechanical & Aerospace Engineering Theses & Dissertations
Experiments were conducted in two different stages--general piezoelectric actuator characterization and flow separation control applications. The characterization of the piezoelectric devices was performed in several stages, due to the many variables that affect performance. The first stage of the characterization consisted of tests conducted on 13 different THUNDERTM (thin-layer composite unimorph ferroelectric driver and sensor) configurations. These configurations consisted of a combination of 1, 3, 5, 7, and 9 layers of 25μ thick aluminum as backing material, with and without a top layer of 25μ aluminum. All of these configurations used the same piezoelectric ceramic wafer (PZT-5A) with dimensions …
System Identification And Control Of Cavity Noise Reduction, Chien-Hsun Kuo
System Identification And Control Of Cavity Noise Reduction, Chien-Hsun Kuo
Mechanical & Aerospace Engineering Theses & Dissertations
This dissertation first presents indirect closed-loop system identification through residual whitening, then identifies the cavity noise system and applies controllers to reduce the noise. High speed air flow over the cavity produces a complex oscillatory flow-field and induces pressure oscillations within the cavity. The existence of cavities induces large pressure fluctuations which generate undesirable and loud noise. This may have an adverse effect on the objects, such as reducing the stability and performance of overall system, or damaging the sensitive instruments within the cavity.
System identification is the process of building mathematical models of dynamical systems based on the available …
Reduction Of Thermal Deflection And Random Response Of Composite Structures With Embedded Shape Memory Alloy At Elevated Temperature, Zhiwei Zhong
Mechanical & Aerospace Engineering Theses & Dissertations
A feasibility study on the reduction of thermal deflection and random response of the composite structures using shape memory alloys (SMA) at elevated temperatures is presented in this dissertation. The characteristics of SMA are introduced and the structural problems, static and dynamic, of SMA fiber reinforced composites are investigated. The stress-strain relations are developed for a composite lamina with embedded SMA fibers. The finite element system equations including shape memory effect are derived. A consistent two-step solution procedure is developed for solving the static and dynamic problems of composite structures with embedded SMA fibers subjected to combined acoustic and thermal …
Inversion And Analysis Of Remotely Sensed Atmospheric Water Vapor Measurements At 940nm, Jack Cutler Larsen
Inversion And Analysis Of Remotely Sensed Atmospheric Water Vapor Measurements At 940nm, Jack Cutler Larsen
Mechanical & Aerospace Engineering Theses & Dissertations
The understanding and acceptance of remotely sensed atmospheric data depends strongly on the steps taken to characterize experiment error and validate observations through comparisons to other independent measurements. A formal error analysis of the Stratospheric Aerosol and Gas Experiment II (SAGE II) water vapor operational inversion algorithm is performed and compared to previous results. Random measurement errors were characterized by segmented least-squares profile fitting of the slant path absorption which found the error to be uncorrelated in the stratosphere with estimated variances significantly smaller than expected from 18-30 km. Estimates of null space error were developed from radiosonde hygrometers in …
Numerical Study Of Three-Dimensional Free Convection From Semi-Enclosed Geometry And Discontinuous Heat Sources, Aklilu T.G. Giorges
Numerical Study Of Three-Dimensional Free Convection From Semi-Enclosed Geometry And Discontinuous Heat Sources, Aklilu T.G. Giorges
Dissertations
Three-dimensional natural convection from three-by-three array of isoflux heat sources mounted on one vertical wall of semi-enclosed region has been numerically investigated. Detailed thermal information of this important engineering configuration is currently not available. The major objective of this study was to obtain this needed thermal and velocity information.
The semi-enclosed geometry can be viewed as a thin rectangular region with four closed and two open sides. The open surfaces are located at the top and adjacent side. For the fluid air, Pr = 0.71, the study covered a heat flux based Rayleigh number (Ra) range of (102 ≤ …
Dynamic Friction Measurement, Modeling, And Compensation For Precise Motion Control, Simon Cohn
Dynamic Friction Measurement, Modeling, And Compensation For Precise Motion Control, Simon Cohn
Theses
In this thesis, measurements of dynamic friction in a hydrodynamic journal bearing were performed for varying sinusoidal velocity excitations, loads, and lubricants. The results indicate that the friction data displays a negative slope in the mixed region of friction vs. velocity (f-v) curves, and also shows that the dynamic friction is not just a function of current velocity, but also a function of velocity history (hysteresis). These results are in agreement with previous experimental investigations by other investigators in lubricated friction.
Secondly, a dynamic friction model is fully explored and partially extended to provide quantitative agreement to measured friction values. …
Optimal Synthesis Of A Planar Four-Bar Function Generator Based On Imderect Measure Of Structural Error, Robert Ellis
Optimal Synthesis Of A Planar Four-Bar Function Generator Based On Imderect Measure Of Structural Error, Robert Ellis
Theses
A novel technique for optimal synthesis of a planar four-bar function generator is presented. An indirect measure of structural error is used to formulate an objective function which, along with its derivatives, is straightforward to evaluate and results in an elegant and robust algorithm. Lagrange multipliers are used to incorporate the loop closure constraint into the objective function.
In this thesis, the formulation of the objective function and the minimization algorithm are described, examples are presented, and the virtues and shortcomings of the algorithm are discussed.
Kinematic Analysis Of A Swash-Plate Mechanism Using Transformation Matrices, David Edgar Evans
Kinematic Analysis Of A Swash-Plate Mechanism Using Transformation Matrices, David Edgar Evans
Theses
The swash-plate mechanism is used to transfer rotational motion into translational motion and vice versa. Using transformation matrices to describe each joint, the displacements of the swash-plate mechanism were analyzed. The general transformation matrix model for the plane joint, not previously developed using transformation matrices, was presented. The solution was tested using a computer program. Examples of three different swash-plate angles; 10, 45, and 25' were considered. The solution was found to agree with previous solutions while offering a more complete description of the mechanism. Future work in this area could include a complete static, velocity, and/or dynamic analysis of …
Parameter Optimization For Curl Distortion In Building Parts Using 3-D Laser Stereolithography, Laurel A. Hanesian
Parameter Optimization For Curl Distortion In Building Parts Using 3-D Laser Stereolithography, Laurel A. Hanesian
Theses
The curl distortions in rapid prototyping using 3-D laser stereo lithography occur as the top layers shrink after being drawn and attaching to the bottom layers. The amount of curl is dependent upon the how much shrinkage the layer has finished prior to adhesion. It is also dependent on how deep the cure of the top layer amounts to as it adheres into the bottom layer. This thesis investigated the effect of build parameters on the distortions associated with the diagnostic 'Letter-H' shaped test part. The same parameters were also considered in a time optimization study, using calculated, predicted results …
Virtual Reality Modelling Of A Cnc Machine, Damian O'Sullivan
Virtual Reality Modelling Of A Cnc Machine, Damian O'Sullivan
Theses
The increasing importance of training and upgrading skills has led to the use of new interactive technologies in the development of more effective training tools. Previous techniques for training Computer Numerical Control (CNC) machine operators, while excellent for their time, varied from brief inexpensive tutorials to expensive on the job training. A CNC machine uses a computer to perform the functions of the machine using a part program stored in the memory of the computer. This thesis describes a Virtual Reality (VR) model of a CNC milling machine, implemented within a VR environment representing a CNC workshop. Its development and …
An Investigation Using The Finite Element Method Into Bowing & Lean Of The 3rd Stage Turbine Blade Of The Pratt & Whitney Jt8d Gas Turbine Engine, Kevin O'Donoghue
An Investigation Using The Finite Element Method Into Bowing & Lean Of The 3rd Stage Turbine Blade Of The Pratt & Whitney Jt8d Gas Turbine Engine, Kevin O'Donoghue
Theses
Following a recent series of failures of overhauled third stage turbine blades in the JT8D- 15A gas turbine engine, new inspection criteria have been introduced by the engine manufacturer Pratt & Whitney. One such inspection checks for airfoil bowing and lean. A blade will bow or lean towards the suction face of the airfoil as a result of creep during engine operation. Third stage turbine blades from the JT8D low pressure turbine have been observed with as much as two millimetres of deflection measured at mid-span. In a geometrically correct T3 blade, the tensile centrifugal load due to engine rotation …
Development Of A Geothermal Heat Pump Test Facility, Chris Collins
Development Of A Geothermal Heat Pump Test Facility, Chris Collins
Theses
Current environmental concerns have led to large scale research and development in the area of alternative energy supplies. The alternative energy system of interest in this study is the heat pump. Heat pumps extract heat from a variety of sources such as air, water and the earth, upgrade and transmit it to the required location. The aim of this thesis is to develop mathematical and experimental models to evaluate the performance of a heat pump which uses the earth as its thermal source. These models will then form the basis of design aids for installers sizing closed loop collection systems …