Mechanical Engineering Commons^™

High Temperature Heat Exchanger Project:Quarterly Progress Report January 1, 2005 Through March 31, 2005, Anthony Hechanova

Publications (NSTD)

Quarterly Collaboration Meeting. Ceramatec, Inc. hosted a UNLVRF HTHX Project quarterly meeting on March 17 in Salt Lake City, Utah. The purpose of the meeting was to promote collaboration and communication among the UNLV Research Foundation partners. Collaborators had the opportunity to discuss their research program plan and update their progress. The next meeting will be in June in San Diego City hosted by General Atomics.

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic: Quarterly Progress Report (Jan. 01 – March. 31, 2005), Yingtao Jiang, Bingmei Fu

Transmutation Sciences Materials (TRP)

We performed data analysis on the data collected from LANL test loop. One student was been hired to perform the data analysis. A new proposal is submitted to TRP program. We have one paper accepted for publication in International Journal of Heat and Mass Transfer, and another paper accepted for oral presentation by IEEE International Symposium of Circuits and Systems for the track Chemical Sensors. A manuscript regarding to the RGA analysis for the calibration of oxygen sensor is on the way.

Electrothermomechanical Modeling Of A Surface-Micromachined Linear Displacement Microactuator, Christian D. Lott

Theses and Dissertations

The electrothermomechanical characteristics of an electrically-heated polycrystallinesilicon microactuator are explored. Using finite-difference techniques, an electrothermal model based on the balance of heat dissipation and heat losses is developed. For accurate simulation, the relevant temperature dependent properties from the microactuator material are included in the model. The electrothermal model accurately predicts the steady-state power required to hold position, and the energy consumed during the thermal transient. Thermomechanical models use the predictions of temperature from the electrothermal solution to calculate displacement and force from pseudo-rigid-body approximations and commercial finite-element code. The models are verified by comparing experimental data to simulation results of …

Characterization Of Crack Propagation During Sonic Ir Inspection, Jacob Kephart, John Chen, Hong Zhang

Mechanical Engineering

Sonic IR is an emerging, thermal-based, nondestructive evaluation (NDE) technique. Typically a short burst of high power acoustical energy is injected into an object being studied and certain types of defects heat up and is detected using a thermal imaging camera. This inspection technique is very fast, lasting only a few seconds for total inspection time. However due to many uncertainties in the inspection process it has yet to be adopted widely by industry. There are many unknown parameters governing sonic IR, which need to be understood before it becomes a widely used NDE technique. This paper shows that under …

Hydrodynamic Drag And Flow Visualization Of Isotruss Lattice Structures, James T. Ayers

Theses and Dissertations

Hydrodynamic drag testing was conducted for eleven different configurations of IsoTruss® lattice structures. Flow visualization of prototypical IsoTruss® wind towers was also performed using Particle Image Velocimetry instrumentation. The drag test and flow visualization specimens included 6-node and 8-node configurations, single and double-grid geometries, thick and thin member sizes, smooth and rough surface finishes, a helical-only structure, and a smaller outer diameter test specimen. Three sets of hydrodynamic drag tests were conducted in a closed-circuit water tunnel: 1) orientation drag tests, 2) water velocity drag tests, and 3) height variation drag tests. The orientation drag tests measured the hydrodynamic drag …

All Hexahedral Meshing Of Multiple Source, Multiple Target, Multiple Axis Geometries Via Automatic Grafting And Sweeping, Matthew N. Earp

Theses and Dissertations

The development of algorithms for the automatic creation of finite element meshes composed entirely of hexahedra (all-hex) is an active area of research. All-hex meshes are desirable for their characteristic of high accuracy with a low node count. Sweeping is one of the most widely used algorithms for generating all-hex meshes. A limitation of sweeping, however, is that it can currently be applied only to prismatic or extruded geometry types. This thesis develops a method to combine sweeping with another algorithm known as "Grafting". Grafting adjusts the mesh on one volume to conform to a second volume. In this manner …

Phase Locked Flow Measurements Of Steady And Unsteady Vortex Generator Jets In A Separating Boundary Layer, Laura C. Hansen

Theses and Dissertations

Vortex generator jets (VGJs) have been found to be an effective method of active separation control on the suction side of a low pressure turbine (LPT) blade at low Reynolds numbers. The flow mechanisms responsible for this control were studied and documented in order to provide a basis for future improvements in LPT design. Data were collected using a stereo PIV system that enabled all three components of velocity to be measured. Steady VGJs were injected into a laminar boundary layer on a flat plate (non-separating boundary layer) in order to more fully understand the characteristics and behavior of the …

Determination Of Wall Thickness And Height When Cutting Various Materials With Wire Electric Discharge Machining Processes, Sangseop Kim

Theses and Dissertations

This thesis looks at the capabilities of cutting thin webs on Wire EDM machines that are difficult or impossible to machine using conventional methods. Covered is an investigation of how different material and web thickness affect the capability of machining thin-walled parts.

Five different metals are used for the test; Aluminum 6061 T6, Yellow Brass SS360, 420 Stainless Steel, D2 unheat-treated tool steel 25-30 RC, and D2 heat-treated tool steel 60-65 RC. The small parts were cut to a 6mm (0.2362 inch) height with six different wall thicknesses: 0.30mm (0.0118 inch), 0.25mm (0.0098 inch), 0.20mm (0.0078 inch), 0.15mm (0.0059 inch), …

A Tool Wear Comparative Study In Turning Versus Computer Simulation In 1018 Steel, Woodrow D. Miner

Theses and Dissertations

The material removal process uses cutting tools in order to produce the desired shape of the workpiece. Tool wear has been a problem for cutting tools, since cutting tools wear and break. Research has been accomplished in the tool wear field for tool life and more recently tool wear. The computer generation has created a method to simulate the material removal process. These computer simulations model the cutting tool reaction with the workpiece. Many of the simulation models use finite element analysis to calculate the reaction of the cutting tool. Different finite element models are being used throughout the world …

Dual-Stage Thermally Actuated Surface-Micromachined Nanopositioners, Neal B. Hubbard

Theses and Dissertations

Nanopositioners have been developed with electrostatic, piezoelectric, magnetic, thermal, and electrochemical actuators. They move with as many as six degrees of freedom; some are composed of multiple stages that stack together. Both macro-scale and micro-scale nanopositioners have been fabricated. A summary of recent research in micropositioning and nanopositioning is presented to set the background for this work. This research project demonstrates that a dual-stage nanopositioner can be created with microelectromechanical systems technology such that the two stages are integrated on a single silicon chip. A nanopositioner is presented that has two stages, one for coarse motion and one for fine …

Developing A Design Space Model Using A Multidisciplinary Design Optimization Schema In A Product Lifecycle Management System To Capture Knowledge For Reuse, Nathaniel Luke Fife

Theses and Dissertations

Parametric strategies for design automation and optimization can have a big impact on engineering design. When parametric tasks and optimization frameworks and methods are combined, theses strategies can be used to make up what is known as a multidisciplinary design optimization (MDO) schema. Knowledge of a design space can be modeled by using a MDO schema to represent the design process. However, current MDO frameworks used to create this schema lack the scope to capture enterprise wide knowledge for reuse and collaboration. Concurrent with the development of MDO, many companies are moving toward increased use of product lifecycle management (PLM). …

Simulation And Assessment Of Air Impingement Cooling On Squared Pin-Fin Heat Sinks Applied In Personal Computers, Hwa-Chong Tien, Wei-Dong Huang

Journal of Marine Science and Technology–Taiwan

The feasibility and effectiveness of air impingement cooling on pin-fin heat sinks applied in personal computers (PC) were investigated numerically in this study. The effects of fin height, fin width, base plate thickness of the heat sink, and ratio of the vertical spacing between the nozzle and the heat sink to jet diameter (z/D) were discussed in detail. For a PC with a P4, 2.8 GHz, 68.4 W CPU, it was found that the cooling effect by using air impingement on a heat sink with z/D = 4 and fin width 4.13 mm for the jet Reynolds number (Re) between …

Statistical Investigation Of Friction Stir Processing Parameter Relationships, Jonathan H. Record

Theses and Dissertations

Friction Stir Welding (FSW) is an emerging joining technology in which basic process understanding is still inadequate. Knowledge of FSW parameter relationships is needed to better understand the process and implement proper machine control. This study utilized a 3-factor, 3-level factorial design of experiments to investigate relationships between key process inputs and measured output parameters. All experiments utilized 7075-T7 aluminum and a threaded pin tool with a 25.4 mm shoulder diameter, 4.76 mm pin length, and 7.9 mm pin diameter. Spindle speed, feed rate, and tool depth were varied throughout 54 welds while X, Y, and Z forces, X torque, …

Simulation-Based Design Under Uncertainty For Compliant Microelectromechanical Systems, Jonathan W. Wittwer

Theses and Dissertations

The high cost of experimentation and product development in the field of microelectromechanical systems (MEMS) has led to a greater emphasis on simulation-based design for increasing first-pass design success and reliability. The use of compliant or flexible mechanisms can help eliminate friction, wear, and backlash, but compliant MEMS are sensitive to variations in material properties and geometry. This dissertation proposes approaches for design stage uncertainty analysis, model validation, and robust optimization of nonlinear compliant MEMS to account for critical process uncertainties including residual stress, layer thicknesses, edge bias, and material stiffness. Methods for simulating and mitigating the effects of non-idealities …

The Purposes And Evaluation Methods For State Residential General Contractor Licensing, James Ellis Fenn

Theses and Dissertations

The main topic in the licensing debate is whether licensing affects construction quality. Available literature and previous studies indicate that it does not. The real question is not whether licensing improves quality, but whether the improving quality is the actual purpose of licensing. There is little information available on the purpose of licensing as defined by state licensing departments as well as a general lack of information on how states evaluate whether licensing is fulfilling the intended purpose. In order to effectively resolve some of the issues surrounding the construction licensing debate, the true purpose of licensing and the methods …

Finite Approximations To The Second-Order Properties Closure In Single Phase Polycrystals, Brent L. Adams, Xiang Gao, Surya R. Kalidindi

Faculty Publications

This work was supported at Brigham Young University and Drexel University by a grant from the US Army Research Office, through the Metallurgy Program headed by Dr. David Stepp. Extension of the first-order theory of microstructure design to considerations of morphological texture is addressed in this paper. The main challenges include the r-interdependence of the 2-point correlation functions of lattice orientation, construction of the corresponding microstructure hull, and its corresponding properties closure(s). It is shown that the correlation functions can be expressed in terms of an intermediate construct, called the texture function; the correlation functions have quadratic dependence in the …

Real-Time Evaluation Of Vision-Based Navigation For Autonomous Landing Of A Rotorcraft Unmanned Aerial Vehicle In A Non-Cooperative Environment, Dale D. Rowley

Theses and Dissertations

Landing a rotorcraft unmanned aerial vehicle (RUAV) without human supervision is a capability that would significantly broaden the usefulness of UAVs. The benefits are even greater if the functionality is expanded to involve landing sites with unknown terrain and a lack of GPS or other positioning aids. Examples of these types of non-cooperative environments could range from remote mountainous regions to an urban building rooftop or a cluttered parking lot. The research of this thesis builds upon an approach that was initiated at NASA Ames Research Center to advance technology in the landing phase of RUAV operations. The approach consists …

Effect Of Edge-Stiffening And Diaphragms On The Reliability Of Bridge Girders, Christopher D. Eamon, Andrzej S. Nowak

Civil and Environmental Engineering Faculty Research Publications

Secondary elements such as barriers, sidewalks, and diaphragms may affect the distribution of live load to bridge girders. The objective of this study is to evaluate their effect on girder reliability if these elements are designed to be sufficiently attached to the bridge so as not to detach under traffic live loads. Simple span, two lane structures are considered, with composite steel girders supporting a reinforced concrete deck. Several representative structures are selected, with various configurations of barriers, sidewalks and diaphragms. Bridge analysis is performed using a finite element procedure. Load and resistance parameters are treated as random variables. Random …

A Systematic Method For Characterizing The Elastic Properties And Adhesion Of A Thin Polymer Membrane, Bing Feng Ju, Yang Ju, Masumi Saka, Kuo Kang Liu, Kai Tak Wan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

The elastic properties and adhesion of a thin silicone rubber membrane have been characterized. an effective instrumentation embodying a video-enhanced microscope, which meets force and displacement resolution of 0.1μN and 10 nm, was developed. It provides the capability of simultaneously measuring both the applied force and the resultant displacement of the thin polymer membrane. a linear theoretical elastic solution was applied to quantitatively interpret the measured central deflection of the membrane under a circular concentrical load. Young's modulus of the membrane can be easily determined once the applied force and the central deflection, together with the essential dimensions, are known. …

Using Multiple Mems Imus To Form A Distributed Inertial Measurement Unit, Ryan D. Hanson

Theses and Dissertations

MEMS IMUs are readily available in quantity and have extraordinary advantages over conventional IMUs in size, weight, cost, and power consumption. However, the poor performance of MEMS IMUs limits their use in more demanding military applications. It is desired to use multiple distributed MEMS IMUs to simulate the performance of a single, more costly IMU, using the theory behind Gyro-Free IMUs. A Gyro-Free IMU (GF-IMU) uses a configuration of accelerometers only to measure the three accelerations and three angular rotations of a rigid body in 3-D space. Theoretically, almost any configuration of six distributed accelerometers yields sufficient measurements to solve …

Head Tracking For 3d Audio Using A Gps-Aided Mems Imu, Jacque M. Joffrion

Theses and Dissertations

Audio systems have been developed which use stereo headphones to project sound in three dimensions. When using these 3D audio systems, audio cues sound like they are originating from a particular direction. There is a desire to apply 3D audio to general aviation applications, such as projecting control tower transmissions in the direction of the tower or providing an audio orientation cue for VFR pilots who find themselves in emergency zero-visibility conditions. 3D audio systems, however, require real-time knowledge of the pilot's head orientation in order to be effective. This research describes the development and testing of a low-cost head …

Detection Of Residual Stress In Sic Mems Using Μ-Raman Spectroscopy, John C. Zingarelli

Theses and Dissertations

Micro-Raman (µ-Raman) spectroscopy is used to measure residual stress in two silicon carbide (SiC) poly-types: single-crystal, hexagonally symmetric 6H-SiC, and polycrystalline, cubic 3C-SiC thin films deposited on Si substrates. Both are used in micro-electrical-mechanical systems (MEMS) devices. By employing an incorporated piezoelectric stage with submicron positioning capabilities along with the Raman spectral acquisition, spatial scans are performed to reveal areas in the 6H-SiC MEMS structures that contain residual stress. Shifts in the transverse optical (TO) Stokes peaks of up to 2 cm^-1 are correlated to the material strain induced by the MEMS fabrication process through the development of phonon …

Application Of Nonlinear Dynamics Tools For Diagnosis Of Cracked Rotor Vibration Signatures, Jerzy T. Sawicki, Xi Wu, Andrew L. Gyekenyesi, George Y. Baaklini

Mechanical Engineering

The nonlinear model of the cracked Jeffcott rotor is investigated, with the particular focus on study of rotor’s vibrational response using tools of nonlinear dynamics. The considered model accounts for nonlinear behavior of the crack and coupling between lateral and torsional modes of vibrations. Load torque is applied to the rotor which is laterally loadedwith a constant radial force (gravity force) and unbalance excitation. The co-existence of frequencies of lateral modes in the frequency spectra of torsional mode are characteristics of the coupling response of lateral and torsional vibrations. When only the lateral excitations are applied, vibration amplitude bifurcation plot …

Effect Of Tensile Offset Angles On Micro/Nanoscale Tensile Testing, Xiaodong Li, Xinnan Wang, Wei-Che Chang, Yuh-Jin Chao, Ming Chang

Faculty Publications

For one-dimensional (1D) structures such as tubes, wires, and beams, tensile testing is a simple and reliable methodology for measuring their mechanical properties. The tensile offset angle effect on mechanical property measurement has long been ignored. In this study, theoretical and finite-element analysis(FEA) models for analyzing the tensile offset angle effect have been established. It is found that longitudinal stress decreases with increasing offset angles. The theoretically calculated elastic modulus relative errors reach 4.45% at the offset angle of 10°, whereas the experimentally measured elastic modulus relative errors are 45.4% at the offset angle of 15°. The difference in elastic …

Aspects Of The Morphological Evolution In Thermal Barrier Coatings And The Intrinsic Thermal Mismatch Therein, J. Shi, S. Darzens, Anette M. Karlsson

Mechanical Engineering Faculty Publications

The evolution of interfacial deformations and stresses in thermal barrier coatings due to the formation of the thermally grown oxide and the intrinsic thermal mismatch is investigated. The study focuses on systems that are prone to displacement instabilities of the thermally grown oxide and numerical models spanning a range of properties are investigated. Material changes in the Pt-modified aluminide bond-coat, such as martensitic transformation and the change from β- to γ′-grains, are considered. The numerical simulations show that when the mismatch is large enough to cause overall yielding in the bond-coat, the thermal expansion of the substrate (the superalloy) will …

Modelling And Validation Of A Propellant Mixer For Controller Design, Hanz Richter, Enrique Barbieri, Fernando Figueroa Nasa Stennis Space Center

Mechanical Engineering Faculty Publications

A mixing chamber used in rocket engine testing at the NASA Stennis Space Center is modelled by a system of two nonlinear ordinary differential equations. The mixer is used to condition the thermodynamic properties of cryogenic liquid propellant by controlled injection of the same substance in the gaseous phase. The three inputs of the mixer are the positions of the valves regulating the liquid and gas flows at the inlets, and the position of the exit valve regulating the flow of conditioned propellant. Mixer operation during a test requires the regulation of its internal pressure, exit mass flow, and exit …

Fabrication Of Hollow Waveguides With Sacrificial Aluminum Cores, John P. Barber, Donald B. Conkey, Jeffrey Ryan Lee, Neal B. Hubbard, Larry L. Howell, Aaron R. Hawkins, Gongliang Yin, Holger Schmidt

Faculty Publications

We have developed a process to fabricate dielectric waveguide structures with long hollow cores formed by etching a sacrificial core material. The process is compatible with other planar silicon fabrication techniques. Using aluminum as the sacrificial material, we have investigated fabrication limits and design parameters that determine mechanical integrity of the waveguides. Internal pressure due to the production of gaseous compounds during the core removal process was identified as the yield-limiting factor. A mechanical model based on finite element analysis and confirmed by experiment, predicts ultimate pressures sustainable by these structures. Waveguides less than 10 m wide with 2- m-thick …

Working Postures Of Dentists And Dental Hygienists, Richard W. Marklin, Kevin Cherney

Mechanical Engineering Faculty Research and Publications

A joint study was conducted by a manufacturer of dental stools in the Midwest of the United

States and Marquette University to measure the occupational postures of dentists and dental hygienists. The postures of 10 dentists and 10 dental hygienists were assessed using work sampling and video techniques. Postura! data of the neck, shoulders and lower back were recorded from video and categorized into 30-degree intervals: O (neutral posture of respective joint), 30, 60 and 90 degrees. Each subject's postures were observed while they were treating patients during a four-hour period, during which 100 observations of postures were recorded at …

Experimental Technique For Studying High-Temperature Phase Equilibria In Reactive Molten Metal Based Systems, Alexandre Ermoline

Dissertations

The general objective of this work is to develop an experimental technique for studying the high-temperature phase compositions and phase equilibria in molten metal-based binary and ternary systems, such as Zr-O-N, B-N-O, Al-O, and others. A specific material system of Zr-O-N was selected for studying and testing this technique.

The information about the high-temperature phase equilibria in reactive metal-based systems is scarce and their studying is difficult because of chemical reactions occurring between samples and essentially any container materials, and causing contamination of the system.

Containerless microgravity experiments for studying equilibria in molten metal-gas systems were designed to be conducted …

Computational Studies Of Viscoelastic Multiphase Flows, Shriram B. Pillapakkam

Dissertations

A finite element code based on the level set method is developed for performing two and three dimensional direct numerical simulations (DNS) of viscoelastic two-phase flow problems. The Oldroyd-B constitutive equation is used to model the viscoelastic liquid. The code is used to study transient and steady state shapes of Newtonian and viscoelastic drops in simple shear and buoyancy driven flows. The roles of the governing dimensionless parameters: Capillary number (Ca), Deborah Number (De) and the polymer concentration parameter c, in determining deformation of drops and bubbles, are also analyzed.

The numerical code permits us to vary Ca, De and …