Mechanical Engineering Commons^™

Mar 2003, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Foundations Liason Report Development Projects Report Report to the Director

An Approach To Concept Development For Compliant Mechanisms Possessing High Coefficients Of Restitution, Brandon H. Woolley

Theses and Dissertations

The design of structures and mechanisms subject to impact loading has historically involved designing in such a way as to minimize damage induced by the impact. This has historically been accomplished by absorbing and dissipating the energy of the impact. However, in some applications it is desirable to harness the energy and return it to the impacting object to maximize the coefficient of restitution (COR), resulting in large rebound velocities. The use of traditional rigid-body mechanisms to achieve high-COR mechanisms is limited by issues of friction, durability, poor strain-energy distribution and others. Compliant mechanisms do not possess the same limitations …

Modeling, Fabrication, And Optimization Of Niobium Cavities Phase Ii: Third Quarterly Report, Robert A. Schill Jr., Mohamed Trabia

Transmutation Sciences Materials (TRP)

Niobium cavities are important parts of the integrated NC/SC high-power linacs. Over the years, researchers in several countries have tested various cavity shapes. They concluded that elliptically shaped cells are the most appropriate shape for superconducting cavities. The need for very clean surfaces lead to the use of a buffered chemical polishing produce for surface cleaning to get good performance of the cavities. The second phase has resulted in an experimental setup of a fluid flow experiment with experimentation to be completed in the third year. Other experimental activities include the evaluation of a vacuum system and various vacuum equipment …

Dynamics Of Asymmetric Nonlinear Vibration Absorber, Chiou-Fong Chung, Chiang-Nan Chang

Journal of Marine Science and Technology–Taiwan

A dynamics of stability and bifurcation analysis of an asymmetrically nonlinear absorber system that contains a main part and a nonlinear spring is proposed. For this study, the analytical works on this nonlinear vibration absorber were performed by the harmonic balance method and the Floquet theory. Dynamic phenomena due to changing of periodic excitation are analyzed. The investigation fulfils that the bifurcation sequences illustrate completely the complex phenomena of system dynamics. Furthermore, this study show that the primary bifurcation orbit coexist with orbit of the secondary responses via a saddle-node bifurcation in a specific period excitation range. The results demonstrate …

On-Chip Actuation Of Compliant Bistable Micro-Mechanisms, Michael S. Baker

Theses and Dissertations

Two compliant bistable micro-mechanisms have been developed which can be switched in either direction using on-chip thermal actuation. The energy storage and bistable behavior of the mechanisms are achieved through the elastic deflection of compliant segments. The pseudo-rigid-body model was used for the compliant mechanism design, and for analysis of the large-deflection flexible segments. To achieve on-chip actuation, the mechanism designs were optimized to reduce their required rotation, allow them to be switched using linear-motion thermal actuators. The modeling theory and analysis are presented for several design iterations. Each iteration was successfully fabricated and tested using either the MUMPs or …

Thermal Microactuators For Microelectromechanical Systems (Mems), Rebecca Cragun

Theses and Dissertations

Microactuators are needed to convert energy into mechanical work at the microscale. Thermal microactuators can be used to produce this needed mechanical work. The purpose of this research was to design, fabricate, and test thermal microactuators for use at the microscale in microelectromechanical systems (MEMS). The microactuators developed were tested to determine the magnitude of their deflection and estimate their force. Five groups of thermal microactuators were designed and tested. All of the groups used the geometrically constrained expansion of various segments to produce their deflection. The first group, Thermal Expansion Devices (TEDs), produced a rotational displacement and had deflections …

An Investigation Of Compliant Over-Running Ratchet And Pawl Clutches, Gregory Mark Roach

Theses and Dissertations

This thesis proposes that compliant mechanism theory can be used to design over-running ratchet and pawl clutches with reduced part count, lower assembly and manufacturing time while maintaining functionality. An extension of the theory to the micro regime is also briefly addressed. The results of the research show that the ratchet and pawl type of over-running clutch is a good choice for the use of compliance, and the clutch pawls should be loaded in compression to get the largest amount of output torque. It was found that com-pliant mechanism theory can be used to design ratchet and pawl clutches with …

Optomechanical Properties Of Stretched Polymer Dispersed Liquid Crystal Films For Scattering Polarizer Applications, Iciro Amimori, Nikolai V. Priezjev, Robert A. Pelcovits, Gregory P. Crawford

Mechanical and Materials Engineering Faculty Publications

A scattering polarizer is created by subjecting a polymer dispersed liquid crystal (PDLC) film to tensile strain. The optomechanical properties of the film are investigated by simultaneously measuring the stress-strain and polarization dependent optical transmission characteristics. The correlation between transmittances of two orthogonal polarizations and the stress-strain curve reveals that the polymer orientation as well as the droplet shape anisotropy influences the liquid crystal alignment within the droplets. A Monte-Carlo simulation based on the Lebwohl-Lasher model is used to explain the subtle influence of polymer orientation on liquid crystal alignment.

Mechanical Computing In Microelectromechanical Systems (Mems), Kenneth C. Bradley

Theses and Dissertations

Mechanical computing devices in polysilicon-based microelectromechanical systems (MEMS) were designed with the goal of developing computing devices for harsh environments, such as those with high dose radiation and high temperatures, as well as devices that may be able to interface with molecular or biological computer systems. The devices that were designed include both analog and digital computing devices. The analog devices include integrators, differentials (summers), multipliers, and those that perform trigonometric functions. The digital devices that were designed are inverters, NAND, NOR, and XOR logic gates. Analog-to-digital (A-to-D) and digital-to-analog (D-to-A) converters were also designed. The designs were submitted to …

Advances In Experimental Method And Analysis For Estimation Of Geometrically-Necessary Dislocations, Brent L. Adams, Bassem S. El-Dasher, Anthony D. Rollett

Faculty Publications

The authors wish to thank The Alcoa Technical Research Center for supplying the specimens and performing the compression tests. This work was supported by the MRSEC program of the National Science Foundation under DMR-0079996 as well as Lawrence Livermore Laboratory DOE/DoD Joint Program. An behavior of grain boundaries of the polycrystalline materials over a wide range of length scales during plastic deformation is considered. Electron backscattering diffraction and orientation imaging microscopy provide automated scanning measurements of the lattice orientation near grain boundaries. These methods are useful to set the necessary length scales. The data are presented for directionally-solidified pure Al …

Microstructural Study Of Nanoprecipitates In Rra Treated Al-7075 T6 Using Afm/Ufm/Stem, Samuel J.M. Kuhr, Margaret Pinnell, Daniel Eylon

Mechanical and Aerospace Engineering Faculty Publications

7075 T651 aluminum alloy is frequently used in aircraft applications for its high strength to weight ratio. However, aircraft parts made of this alloy have been plagued by stress corrosion cracking (SCC). Retrogression and re-aging (RRA) is a post T651 two-stage heat treatment that provides improved SCC resistance with minimal loss in tensile strength. In this study, various forms of microscopy and mechanical testing are used to investigate how the RRA process affects the microstructure.

The microscopic observations in this paper show that the precipitates in the aluminum alloy coarsen and that the grain boundary regions are depleted of copper …

A Joint Trajectory Generator For Motion Recovery, Edward Red, Wei Li

Faculty Publications

This paper describes an adaptive S-curve used to recover a tool path upon a system crash in the Windows operating system (OS). For a mechanism such as a robot or machine tool, the joint values, being delivered as setpoints to the servo-controller, are dynamically recorded by the real-time operating system also residing on the computer. The real-time OS can control the abort and record pertinent motion data after Windows OS crash.

The Effects Of Ionizing Radiation On Microelectromechanical Systems (Mems) Actuators: Electrostatic, Electrothermal, And Residual Stress, Jared R. Caffey

Theses and Dissertations

The effects of ionizing radiation on the operation of polysilicon mmicroelectromechanical system (MEMS) electrostatic actuators, electrothermal actuators, and residual stress cantilevers were examined. Pre-irradiation, in-situ, and post-irradiation measurements were taken for the electrosatic and electrothermal actuators. The residual stress cantilevers were characterized before and after irradiation. All devices were irradiated to a total ionizing does of 1 megarad(Si) using both the Air Force Research Laboratory's low energy X-ray source and Co-60 gamma source.

Use Of Positron Annihilation Spectroscopy For Stress-Strain Measurements, Ajit K. Roy

Transmutation Sciences Materials (TRP)

The purpose of this collaborative research project involving the University of Nevada, Las Vegas (UNLV) and the Idaho State University (ISU) is to evaluate the feasibility of determining residual stresses of welded, bent (three-point-bend), and cold-worked engineering materials using a new nondestructive technique based on positron annihilation spectroscopy. The proposed technique is to use x-rays from a small MeV electron Linac to generate positrons inside the sample via pair production. This method can be used for materials characterization and investigation of defects in thick samples that could not be accomplished by conventional positron technique or other nondestructive methods. The data …

Design And Analysis Of A Process For Melt Casting Metallic Fuel Pins Incorporating Volatile Actinides, Yitung Chen, Darrell Pepper, Randy Clarksean

Fuels Campaign (TRP)

UNLV has developed and will continue to develop process models for the analysis of melt casting processes. This work will continue to be performed under the guidance of Argonne National Laboratory (ANL) engineers to insure that their knowledge and experience benefits the project. The research to be conducted during year three will center on performing detailed analyses on a conceptual design of an inductively heated skull-crucible casting furnace. Processing conditions will be analyzed, basic models utilized, and detailed heat and mass transfer models will be developed to analyze the most promising processes. The goal of this third year is to …

Near-Field Calculations For A Rigid Spheroid With An Arbitrary Incident Acoustic Field, John P. Barton, Nicholas L. Wolff, Haifeng Zhang, Constantine Tarawneh

Mechanical Engineering Faculty Publications

A general spheroidal coordinate separation-of-variables solution is developed for the determination of the acoustic pressure distribution near the surface of a rigid spheroid for a monofrequency incident acoustic field of arbitrary character. Calculations are presented, for both the prolate and oblate geometries, demonstrating the effects of incident field orientation and character (plane-wave, spherical wave, cylindrical wave, and focused beam) on the resultant acoustic pressure distribution.

Time Aliasing Methods Of Spectrum Estimation, Jason F. Dahl

Theses and Dissertations

Time aliasing methods of spectrum estimation alter the time representation of a signal for the purpose of improving its frequency domain representation. Time aliasing allows characteristics of longer time window functions to be used with shorter DFT length. Windows designed specifically for use with time aliasing have improved properties compared to conventional windows. Many previous uses of time aliasing, including overlap-and-add methods of digital filtering, have focused on the elimination of time aliasing effects in the frequency domain in order to improve the representation of reconstructed signals in the time domain and have not addressed the issues associated with spectrum …

Sunup To Sundown - Energygauge Usa 2.0, Florida Solar Energy Center, Robin Vieira

FSEC Energy Research Center®

You need special tools to design high-performance homes - residences where energy efficiency creates greater comfort, health, and energy savings. Making decisions about energy efficiency requires the accurate calculation of energy use and demand, and the comprehensive evaluation of proposed improvements.

A new software tool helps meet these requirements. EnergyGauge USA, an hourly simulation tool for the design and analysis of high-performance homes, performs detailed hourly simulation analysis for energy use, ratings and code calculations. Version 2.0 adds many features to the first-generation product, including thermal mass, photovoltaic (PV) system simulation, solar water heating, and detailed hourly outputs.

The software, …

Acoustical Characterization And Parameter Optimization Of Polymeric Noise Control Materials, Emile N. Homsi

Dissertations

The sound transmission loss (STL) characteristics of polymer-based materials are considered. Analytical models that predict, characterize and optimize the STL of polymeric materials, with respect to physical parameters that affect performance, are developed for single layer panel configuration and adapted for layered panel construction with homogenous core. An optimum set of material parameters is selected and translated into practical applications for validation.

Sound attenuating thermoplastic materials designed to be used as barrier systems in the automotive and consumer industries have certain acoustical characteristics that vary in function of the stiffness and density of the selected material. The validity and applicability …

Numerical And Experimental Investigation Of Dry Particle Coating, Ajit Mujumdar

Dissertations

Dry particle coating is an emerging field in the industries that deal with particulate products and powder processing. Compared to the widely reported experimental studies of the dry particle coating, the theoretical modeling of such processes is found to be less comprehensive. The work presented in this thesis is an attempt to fill this gap.

The first part of the dissertation aims at the numerical investigation of the hybridization system (Nara Machinery, Tokyo, Japan). The flow behavior of different materials processed in this device is analyzed using three-dimensional Discrete Element Method (DEM) as well as the computational fluid dynamics (CFD) …

Evaporating Crossflow Sprays In Gas-Solid Flows, Guangliang Liu

Dissertations

Injection of evaporating sprays into gas-solid flows is encountered in many engineering processes such as energy production industry and chemical industry. The phenomenon involves phase change, three-phase interactions, heat and mass transfer. All of these characteristics control the process efficiency, pollutant production and product quality. However, very limited studies are available on the evaporating spray jets in gas-solid flows, especially on the spray evaporation rate within a gas-solid medium. A combined study of experiments and theoretical analysis has been carried out here to investigate the fundamental mechanism of evaporating Crossflow spray jets in gas-solid flows.

In this study, in addition …

Numerical Study Of Pneumatic Conveying Of Powders, Muhammad Mushahid Rafique Quereshi

Theses

The dense phase mode may be advantageous over the dilute phase mode, for some pneumatic conveying problems, because it causes less erosion of the pipeline, less attrition of the material, requires less dust collection and is effective even for smaller pipe diameters. The objective of this study is to numerically determine the parameters that govern the formation slugs in dense phase conveying. The distributed Lagrange multiplier/fictitious domain method (Glowinski et al. 1998 and Singh et al. 2000) is used to perform direct simulations of the motion of solid and gas phases in pipes with rectangular cross-sections. In this approach the …

Electrohydrodynamical Manipulation Of Particles Based On Dielectrophoresis, Oleksii Vasylyschuk

Theses

The movement of matter in a non-uniform electric field, termed dielectrophoresis, is of interest to scientists of various branches: physics, chemistry, engineering, and life science. To chemists and physicists it is a science of many varied phenomena. To engineers it is a source of new and useful techniques for separating materials or improving materials’ behavior. To ecologists it provides a major means of minimizing pollution. To life scientists it offers new ways to study and manipulate cells and their subparticles, and to help unravel the nature of living systems.

The purpose of this thesis is to concentrate on some aspects …

Developing A Sensing System For The Measurement Of Oxygen Concentration In Liquid Pb-Bi Eutectic: Quarterly Progress Report (Nov. 01 – Jan. 31, 2002), Yingtao Jiang, Bingmei Fu, Woosoon Yim

Transmutation Sciences Materials (TRP)

The design of the new apparatus for oxygen measurement/calibration has been completed. This new apparatus shall be of great importance for the UNLV researchers to conduct the research work in the campus.

Implementation Of A Two-Dimensional Discrete Element Method To Describe Granular Materials Composed Of Elliptical Cohesionless Particles, Juan Jose Martinez Alvez

Theses

This work is aimed at developing a discrete element simulation that models the contact between elliptical grains or particles in granular materials. The goal is to implement an algorithm to carry out collision detection between ellipses as well as ellipsoidal objects. The practical issue here is that the real shape of macroscopic grains can be approximated better using elliptical curves than using spherical curves. In addition, the simulation model will also be valid for spheres, since these objects are special cases of ellipsoids.

An accurate contact detection algorithm was investigated by means of two different formulations. The first formulation determines …

Computer Simulation Of Automotive Disc Brake Noise, Vadims Milovs

Theses

Disc brake noise continues to be a major concern throughout the automotive industry despite efforts to reduce its occurrence. Many articles are written on this subject, but there still is no agreement on what exactly causes disc brake noise and what part of the braking system is responsible for it.

The goal of current research was to build a simplified but inclusive mathematical model of a disc brake system and investigate it using Matlab software. The twodimensional model including damping, Stribeck effect and stick-slip friction was built.

The model is unique in a way that all the similar models have …

Jan 2003, Tractor Museum

Lester F. Larsen Tractor Museum: Planning and Development Documents

Interim Director Report Open House Suggested to Open Museum on Saturdays

Body Concept Design For Pedestrian Head Impact, S. Iskander Farooq, Peter J. Schuster

Mechanical Engineering

In 1996, the European Enhanced Vehicle Safety Committee, Working Group 17 (EEVC WG17) proposed -a set of impact procedures to evaluate the pedestrian injury risk of vehicle fronts. These procedures address three aspects of pedestrian protection -head impacts, lower limb impacts, and thigh impacts -through vehicle subsystem tests. The criteria assessed during these impact tests are affected by the design of most parts of the vehicle body front-end.

One of the challenges to vehicle design introduced by these tests is the impact of an adult pedestrian headform to the top of the fender. The proposed acceptance level for Head Injury …

Tools And Metrics For Evaluating Modular Product Concepts Based On Strategic Objectives, Matthew Bailey Strong

Theses and Dissertations

The design of modular products has recently become the focus of significant research in the area of design theory and methodology. This focus is the result of increased awareness of the potential power of modularity to achieve certain product objectives. However, there continues to be a gap between the results of academic research and industrial application. The refinement, consolidation, and extension of this academic research would help design teams who are charged with developing modular products to use these academic findings in real world, industrial applications. The research presented in this document focuses on developing design tools, based on past …

Ultrasonic Technique For Investigation Of The Effect Of Grid-Generated Turbulence On Sound Wave Propagation, Tatiana A. Andreeva, William W. Durgin

Office of the Provost Scholarship

This paper concerns an experimental study of the effects of the grid-generated turbulence on the propagation of acoustical waves in a wind tunnel. Turbulence effects are investigated using ultrasound time-of-flight method, employing counter-propagating ultrasonic pulses. Turbulence effects are an important source of error in the active probing of the atmosphere using sound sources. The emphasis is on the propagation time fluctuations and their interpretation using theoretical analysis of Kolmogorov.