Mechanical Engineering Commons^™

New Product Launch Decisions Under Competition And Uncertainty: A Real Options And Game-Theoretic Approach To New Product Development, James O. Ostler

Theses and Dissertations

New product development is central to many firms' future success. Not only as a means to continue to maintain their piece of the market, but product development can also be a strategic means for a company to diversify, and/or alter focus to adapt to changing market conditions.

Most of the research in new product development has been on how to do it cheaper and faster than the next guy. However, early commercialization does not guarantee a position of strength in the market. Failures of EMI in CT scanners and Xerox in personal computers illustrate that being first to market does …

Dynamic Stability And Handling Qualities Of Small Unmanned-Aerial-Vehicles Unmanned-Aerial-Vehicles, Tyler Michael Foster

Theses and Dissertations

General aircraft dynamic stability theory was used to predict the natural frequencies, damping ratios and time constants of the dynamic modes for three specific small UAVs with wingspans on the scale from 0.6 meters to 1.2 meters. Using USAF DatCom methods, a spreadsheet program for predicting the dynamic stability and handling qualities of small UAVs was created for use in the design stage of new small UAV concept development. This program was verified by inputting data for a Cessna-182, and by then comparing the program output with that of a similar program developed by DAR Corporation. Predictions with acceptable errors …

A Finite Element Simulation Of Temperature And Material Flow In Fricton Stir Welding, Mark J. Lasley

Theses and Dissertations

The purpose of this research was to use the Transvalor S.A. product, Forge3, to develop a finite element simulation of the friction stir welding process that improves the predictability of temperature evolution and material flow within the plunge portion of the process. Previous modeling created more heating within the billet than experimental results, probably due to the simplification of the simulation with adiabatic boundary conditions. More realistic tooling temperatures were included in this model as these affect heat evolution which is a determining factor in microcrystalline growth. These results were validated by experimental efforts using a billet and tooling instrumented …

A Method For Winding Advanced Composites Of Unconventional Shapes Using Continuous And Aligned Fibers, Abraham K. Allen

Theses and Dissertations

Advanced composites are extremely strong, rigid, and light, even when compared with advanced metals. Advanced composites are replacing high-tech metals as the material of choice for aerospace engineering. However, the processes used to manufacture advanced composites generally lose some of the properties of the materials by their process limitations.

One process that keeps the theoretically awesome qualities of the composite materials in tact is filament winding. Filament wound parts are used as rocket shells, bicycle frame tubes, drive shafts, pressure vessels, etc. Filament winding is an automated process and makes reliable parts to close tolerances. If a straight tube were …

An Adaptive Tool-Based Telerobot Control System, Ge Zhang

Doctoral Dissertations

Modern telerobotics concepts seek to improve the work efficiency and quality of remote operations. The unstructured nature of typical remote operational environments makes autonomous operation of telerobotic systems difficult to achieve. Thus, human operators must always remain in the control loop for safety reasons. Remote operations involve tooling interactions with task environment. These interactions can be strong enough to promote unstable operation sometimes leading to system failures. Interestingly, manipulator/tooling dynamic interactions have not been studied in detail. This dissertation introduces a human-machine cooperative telerobotic (HMCTR) system architecture that has the ability to incorporate tooling interaction control and other computer assistance …

Design And Parameter Identification Of A Discrete Variable Transmission System, Kelley Parker Brown

Masters Theses

Complex and expensive electro-hydraulic systems have shouldered the workload for remote cleanup operations in radiological and toxicological areas in the past; the payload, reach and speed requirements of most applications have demanded their use. Electromechanically actuated systems (EAS) however offer an alternative that in comparison is much more reliable and maintainable. The problems faced in implementing the EAS are in high payload operations where the hydraulic systems hold a clear power density advantage. For the EAS to compete in the area of torque, very large DC motors have been implemented which make them obsolete in restricted work space areas and …

Retrieval Of Nano-Size Particles From A Solid Substrate, Krishna Prasad Podila

Masters Theses

The retrieval of nano-size particles from suspects and crime scenes can significantly enhance surveillance and crime investigation. The Thesis deals with extensive study of free surface energy coupled with Hertzian contact energy under different conditions between a nano-sized particle and a substrate and the various methods of dislodging the particle. Using the Johnson-Kendall-Roberts (JKR) theory, a physical spring-mass-damper model is defined. Mathematical equations are formulated and solved with non-linear equations simulating the real world situation. Using Newmark’s β method, the system is solved for response of free and forced vibrations taking moisture to be responsible for damping. Key assumptions such …

Effects Of Pressure And Equivalence Ratio On Minimum Ignition Energies Of Methane-Air Mixtures And Effect Of Pressure On Breakdown Threshold Energies Of Methane And Air, Sameer Vidyadhar Bondre

Masters Theses

An experimental investigation is conducted to determine the effect of pressure on breakdown threshold energies of methane and air. In addition the effect of pressure and equivalence ratios on minimum ignition energies of methane-air mixtures are also investigated. The pressures for the breakdown threshold energy experiments are varied from 0.02 to 1.17 MPa, and pressures and equivalence ratios for minimum ignition energy experiments are varied from 0.1 to 1.04 MPa and 0.6 to 1.2, respectively. The gas breakdown and the ignition of the methane-air mixture is achieved using a laser-induced spark from a 5.5 ns pulse Q-switched Nd:YAG laser at …

Prediction Of Crack Growth Rate And Load Interaction Effects Using Damage Accumulation Model, Virender Goswami

Masters Theses

In damage tolerant designs, it is important to know the crack growth behavior of a material, so that sudden failure of a component can be avoided by determining a safe life. There are numerous models available to predict the crack growth rate. Among them the "crack closure model" is most often used for predicting the crack growth rate for different R-ratios and load interaction effects. However recently, the crack closure model has come under criticism by many authors to be flawed and overrated owing to its inherent drawbacks.

Therefore, a mathematical model for the fatigue crack propagation based on damage …

Cure Behavior Study And Elastic Modulus Characterization Of Resin System Of A Quasi Poloidal Stellarator Modular Coil, Hariharanath Kavuri

Masters Theses

Composites materials are increasingly becoming choice materials because of their tremendous strength-to-weight properties and impressive design flexibility. A more recent application of composites is in nuclear fusion reactors. One such reactor is the Quasi-Poloidal Stellarator (QPS) being developed by Oak Ridge National laboratory. QPS, with a non-axisymmetric, near-poloidally symmetric magnetic configuration, has stranded copper/epoxy composite coils, used for magnetic confinement of plasma. CTD- 404 and CTD-101K are the resins under consideration for the modular coils with copper fiber as reinforcement. Structural integrity of the modular coils over wide range of temperatures, including liquid nitrogen temperature, is of vital importance and …

Lean Nox Trap Catalysis For Lean Burn Natural Gas Engines, Aaron Michael Williams

Masters Theses

As the nation’s demand for energy grows along with concern for the environment, there is a pressing need for cleaner, more efficient forms of energy. The internal combustion engine is well established as one of the most reliable forms of power production. They are commercially available in power ranges from 0.5 kW to 6.5 MW, which make them suitable for a wide range of distributed power applications from small scale residential to large scale industrial. In addition, alternative fuels with domestic abundance, such as natural gas, can play a key role in weaning our nations dependence on foreign oil. Lean …

Stress Corrosion Cracking And Hydrogen Embrittlement Of Martensitic Alloy Ep-823, Mohammad K. Hossain

UNLV Theses, Dissertations, Professional Papers, and Capstones

This investigation is focused on the evaluation of stress corrosion cracking (SCC), localized corrosion, and hydrogen embrittlement (HE) susceptibility of martensitic Alloy EP-823 in neutral and acidic solutions at ambient and elevated temperatures. While no failures were observed in smooth specimens in the neutral solution, failures were noticed in the 90°C acidic solution at constant-load (CL) leading to a threshold stress (O'_th) of 102 ksi. The presence of a notch reduced the O'_th value to 91 ksi in a similar environment. The ductility (%El and %RA), time-to-failure (TTF), and true failure stress (O'_r) were gradually …

Environment Assisted Cracking Of Target Structural Materials Under Different Loading Conditions, Venkataramakrishnan Selvaraj

UNLV Theses, Dissertations, Professional Papers, and Capstones

Martensitic Alloy HT-9 has been tested for its evaluation of stress corrosion cracking resistance in neutral and acidic solutions at ambient and elevated temperatures incorporating smooth and notched cylindrical specimens under constant load and slow strain rate (SSR) conditions. C-ring and U-bend specimens have also been tested for stress corrosion cracking evaluation in the acidic solution. The role of hydrogen on the cracking tendency has been evaluated by cathodic applied potential.

The results of constant load testing enabled the determination of the threshold stress for stress corrosion cracking in susceptible environments. The magnitudes of ductility parameters were reduced with increasing …

Stress Corrosion Cracking Resistance Of Martensitic Stainless Steels For Transmutation Applications, Phani P. Gudipati

UNLV Theses, Dissertations, Professional Papers, and Capstones

The susceptibility of Alloy EP-823 to stress corrosion cracking has been evaluated using smooth and notched cylindrical specimens in neutral and acidic solutions at ambient and elevated temperatures using constant load and slow strain rate testing (SSR) techniques. C-ring and U-bend specimens have also been tested in the acidic solution. The effect of hydrogen on the cracking susceptibility has been evaluated under controlled cathodic potential. While no failures were observed with smooth specimens at constant load, the notched specimens showed failure. The SSR test results indicate that the true failure stress (o'_f), time to failure and ductility parameters …

Cfd Analysis Of 3-D Thermalhydraulics Flow Effects On Wall Concentration Gradient Profiles For Lbe Loop Fittings, Narain Armbya

UNLV Theses, Dissertations, Professional Papers, and Capstones

The objective of the thesis is to study the effects of thermalhydraulics flows on the wall concentration gradient profiles in LBE loop fittings. To that end detailed models of the fittings have been constructed to study these effects. These fittings include sudden expansion, sudden contraction, t-joint and elbow. The typical flow rates chosen for these simulations are typical of design criteria chosen for the loop with Reynolds numbers expected around 200,000 and the usual axial temperature profiles which are being characterized in the DELTA loop at LANL. STAR-CD is the simulation package used to make these predictions, which include detailed …

Introduction To Mechanical Engineering, Lorik Abdullai, Joseph R. Dunn

Honors Theses

I can still remember back in high school when I was faced with a decision thousands of students experience every year: What college was I going to choose, and what major was I going to study? It seemed like every time I saw friends and relatives they asked me that question. Meanwhile, I knew that going to a major university would give me more choices in case I changed majors. As it turned out, Western Michigan University was the best package for me when I considered the financial aid, the program ofmy major, location of the university, and its friendly …

Development Of Pole Impact Testing At Multiple Vehicle Side Locations As Applied To The Ford Taurus Structural Platform, Mark Halford Warner

Theses and Dissertations

A test method was developed whereby repeated pole impacts could be performed at multiple locations per test vehicle, allowing a comparison of energy and crush relationships. Testing was performed on vehicles moving laterally into a 12.75 inch diameter rigid pole barrier. Crush energy absorption characteristics at the different locations were analyzed, and the results compared to test data from broad moving barrier crashes and available crash tests with similar pole impacts. The research documents the crush stiffness characteristics for narrow impacts at various points on the side of the Taurus vehicle platform. Factors encountered during the research include the importance …

The Effectiveness Of Computer-Based Tutorials In Learning Computer-Aided Design Methods For Tool Design Procedures, Andrew Moroni Hall

Theses and Dissertations

Throughout the past twenty-five years the process of designing and manufacturing a product has been revolutionized by the integration of Computer Aided Design (CAD). Although three-dimensional solid modeling, or 3-D CAD offers a better representation of the product in a virtual environment, it can be complicated and difficult to learn. Tutorials have been developed to assist manufacturing tool design student in the learning of 3-D CAD principles as they apply to tool design. This study seeks to test the effectiveness of those tutorials. A BYU tool design class was divided into two groups according to their assigned laboratory time. The …

Compliant Mechanisms To Perform Bearing And Spring Function In High Precision Applications, Jesse R. Cannon

Theses and Dissertations

An increasing number of mechanical systems are being designed on the micro and meso scales. Assembly and maintenance become increasingly difficult as the size of mechanisms decrease, and the minimum size of traditional elements such as bearings and springs is limited. The backlash of bearings also limits their usefulness in applications where high precision and repeatability are needed. At small scales and for high precision applications, alternative, non-traditional elements are needed.

The objective of this thesis is to develop reliable and scalable compliant components to replace bearings and helical springs. Components replacing springs must be able to produce specified torque/motion …

Thermally Developing Electro-Osmotic Convection In Circular Microchannels, Spencer L. Broderick

Theses and Dissertations

Thermally developing, electro-osmotically generated flow has been analyzed for a circular microtube under imposed constant wall temperature (CWT) and constant wall heat flux (CHF) boundary conditions. Established by a voltage potential gradient along the length of the microtube, the hydrodynamics of such a flow dictate either a slug flow velocity profile (under conditions of large tube radius-to-Debye length ratio, a/lambda_d) or a family of electro-osmotic flow (EOF) velocity profiles that depend on a/lambda_d. The imposed voltage gradient results in Joule heating in the fluid with an associated volumetric source of energy. For this scenario coupled with a slug flow velocity …

Analysis Of Power Takeoff Shafts To Prevent Injuries/Fatalities, Naomi Bronson

Morehead State Theses and Dissertations

A thesis presented to the faculty of the College of Science and Technology at Morehead State University in partial fulfillment of the requirement for the Degree of Master of Science by Naomi Bronson on November 1, 2004.

Quantifying The Effects Of Aging On The Mechanical Properties Of Medical Grade Polycarbonate And Uv Cured Adhesives, Christopher James Lewis

Theses and Dissertations

Advances in engineering polymer technology have created a generation of high strength-to-weight materials for medical applications, with virtually no adverse interactions with body fluids. Polycarbonate is a widely used engineering polymer, and is often used in connection with ultra-violet light (UV) cured adhesives. Because of the chemical complexity of polymers, little is known about their actual aging characteristics. By characterizing the effects of aging, storage environment, and sterilization on medical grade polycarbonate/adhesive system properties, more accurate failure predictions can be made. In this thesis, efforts to better understand the effects of accelerated aging on a medical grade polycarbonate and UV …

A Cad-Centric Approach To Cfd Analysis With Discrete Features, Matthew Lee King

Theses and Dissertations

During the conceptual design stage several concepts are generated, and a few are selected for detailed analyses. CAD models from conceptual design often follow the "over-the-wall" approach for downstream analyses such as FEA, CFD, heat transfer, and vibrations. A CAD-centric approach will be applied to the CAD-to-CFD process to help industry in an ongoing quest to shorten the design cycle time. The CAD-centric approach consists of using the CAD model as a source of data for downstream applications such as mesh generation, and CFD setup. The CAD model used in the CAD-centric approach contains the geometry to be analyzed and …

Development Of A Virtually Calibrated Projection Moire Interferometry Technique Capable Of Inaccessible Surface Measurements, Mark Lee Kimber

Theses and Dissertations

Optical-based techniques have found merit in measuring displacement and strain for decades. These techniques are commonly used in numerous applications ranging from large displacements in wind tunnel experiments to displacement measurements on the submicron scale. Projection Moiré Interferometry (PMI) is an out-of-plane displacement measurement technique, and consists of capturing reference and deformed images of a grid pattern projected on the test object. By differencing the reference and deformed images of the projected grid pattern, a fringe pattern is generated from which the displacement field can be extracted. This computation requires calibration procedures that analyze a number of fringe patterns from …

Variation Simulation Of Fixtured Assembly Processes For Compliant Structures Using Piecewise-Linear Analysis, Michael L. Stewart

Theses and Dissertations

While variation analysis methods for compliant assemblies are not new, little has been done to include the effects of multi-step, fixtured assembly processes. This thesis introduces a new method to statistically analyze compliant part assembly processes using fixtures. This method, consistent with the FASTA method developed at BYU, yields both a mean and a variant solution. The method, called Piecewise-Linear Elastic Analysis, or PLEA, is developed for predicting the residual stress, deformation and springback variation in compliant assemblies. A comprehensive, step-by-step analysis map is provided. PLEA is validated on a simple, laboratory assembly and a more complex, production assembly. Significant …

Layer-By-Layer Nanoassembly Combined With Microfabrication Techniques For Microelectronics And Microelectromechanical Systems, Jingshi Shi

Doctoral Dissertations

The objective of this work is to investigate the combination of layer-by-layer self-assembly with microfabrication technology and its applications in microelectronics and MEMS.

One can assemble, on a standard silicon wafer, needed multilayers containing different nanoparticles and polymers and then apply various micromanufacturing techniques to form microdevices with nanostructured elements.

Alternate layer-by-layer self-assembly of linear polyions and colloidal silica at elevated temperatures have been firstly studied by QCM and SEM. LbL self-assembly and photolithography were combined to fabricate an indium resistor. The RTA method was employed in the fabrication. Hot-embossing technique as a reasonably fast and moderately expensive technique was …

The Benefit Of Using Simulation To Improve The Implementation Of Lean Manufacturing Case Study: Quick Changeovers To Allow Level Loading Of The Assembly Line, Jack J. Mcclellan

Theses and Dissertations

In today's competitive manufacturing environment, companies are constantly looking for ways to improve. Because of this, many companies are striving to become "lean" by implementing lean manufacturing, which is a difficult process. To aid in the implementation of lean manufacturing, simulation was used to reduce the trial-and-error period of lean manufacturing and find to optimum approach to implement the lean manufacturing principle. In this research, a case study of implementing level loading of the production schedule for BullFrog International, L.C. will be examined. To make it possible to implement level loading, the thermo-former machine at the beginning of the operations …

A Review Of Setup Practices And Procedures For Creating Ieee 802.11 Wireless Community Networks, Jae M. Theobald

Theses and Dissertations

IEEE 802.11 wireless networking equipment has made it possible to bridge the last mile for new broadband internet service providers. Inexpensive wireless networking equipment and high gain antennas enable high speed internet delivery at a fraction of the cost of installing or upgrading land lines for cable or DSL services. Based on this research, a guide of general practices and procedures is proposed for designing, installing, and maintaining a reliable wireless community area network. Included tests have provided performance results for several types of wireless antennas (including wire grid parabolic dishes, Yagi and Vagi styles, and echo backfire), wireless bridges, …

Numerical Simulations In Electro-Osmotic Flow, Joseph S. Tenny

Theses and Dissertations

The developing flow field in a parallel plate microchannel, induced by wall motion, has been modeled numerically. This type of flow simulates the physical driving mechanism that exists in electro-osmotically generated flow with large channel diameter-to-Debye length ratios (Z). The physics of the flow field were compared between the moving wall model (MWM) and electro-osmotic flow (EOF) at Reynolds numbers of 1 and 1800, and Z > 2500. Also, Z-values between 50 and 500 were studied to investigate the accuracy of the MWM. Results show that for Z-values greater than 100 the MWM shows good agreement with EOF.

The dynamics of …

An Open Architecture For Versatile Machine And Actuator Control, Michael Scott Baxter

Theses and Dissertations

Automatic control technology increases usability, reliability and productivity in manufacturing, transportation, and climate control. There are many additional areas of modern life that could benefit through automatic control; however, current automation components are too expensive or aren't sufficiently flexible. For example, the cost of current commercial motion control components precludes their use in an average home. This thesis describes an automatic control methodology that is low cost and is flexible enough for a wide variety of control applications. Typical applications could include:

- Home lighting, security and appliances

- Commercial building heating, ventilation and air conditioning

- Industrial machine tool …