Mechanical Engineering Commons^™

Incorporating Grain Size Effects In Taylor Crystal Plasticity, Bradley S. Fromm

Theses and Dissertations

A method to incorporate grain size effects into crystal plasticity is presented. The classical Hall-Petch equation inaccurately predicts the macroscopic yield strength for materials with non-equiaxed grains or materials that contain unequal grain size distributions. These deficiencies can be overcome by incorporating both grain size and orientation characteristics into crystal plasticity theory. Homogenization relationships based on a viscoplastic Taylor-like approach are introduced along with a new function, the grain size and orientation distribution function (GSODF). Estimates of the GSODF for high purity α-titanium are recovered through orientation imaging microscopy coupled with the chord length distribution. A comparison between the new …

Bio-Surfaces And Geometric References For A Standardized Biomechanical Design Methodology For Mass Customization, Kimberly A. Jensen

Theses and Dissertations

This dissertation presents a method for the design of customizable products that interface with the human body. The method presented involves first, a consistent method of capturing and representing the human model so that the model can be used with CAx tools and solid modeling techniques. Second, it provides a design methodology based on feature structure planning and assembly modeling that provides a consistent structure to the design process so that it can be reused and parameterized. Third, a strategy for identifying parametric variables that are referenced to the human body is introduced. The core of this method is the …

Reducing Curvature In Complex Tool Paths By Deviating From Cam-Produced Tool Paths Within A Tolerance Band, George Benjamin Naseath

Theses and Dissertations

This thesis develops an algorithm to decrease high-curvature sections in tool paths for complex parts to achieve shorter machining times resulting in higher production rates. In the research sample cases, the algorithm decreased machining times by 1% to 9% for design-induced sections of high curvature and by 16% to 75% for CAM induced ripples using high path tolerances. High-curvature sections in tool paths are caused by complex part geometry, noise, and discontinuities in the model. The curvature is decreased by deviating the tool path within an allowable path tolerance. The feedrate along the tool path is directly related to the …

One-Dimensional Radial Flow Turbomachinery Performance Modeling, Robert John Pelton

Theses and Dissertations

The Two-Element In Series (TEIS) and Two-Zone models have been used successfully for over twenty years to model test data for radial flow compressors and pumps. The models can also be used to predict the performance of new machines provided that the model inputs can be accurately specified. Unfortunately, use of the TEIS and Two-Zone models as a predictive tool has been limited because an accurate and broadly applicable method of predicting the modeling parameters, etaA, etaB, chi and d2p does not exist. Empirical models have been developed to predict the TEIS and Two-Zone modeling parameters based on a large …

Investigation Of Vorticity Confinement As A High Reynolds Number Turbulence Model, Nicholas F. Lynn

Doctoral Dissertations

Vorticity Confinement (VC) is a computational technique used to compute fluid flows with thin vortical regions in an accurate and efficient manner. Recent results have shown that it accurately computes the turbulent wake behind blunt bodies at large Reynolds numbers. Physically, these flows are dominated by thin vortices that convect downstream with the flow, which accounts for the important higher-order velocity statistics. These thin vortices are artificially dissipated with traditional methods, whereas VC can accurately compute them.

VC consists of a set of discrete equations with the confinement appearing as a source term in the discretized momentum equations. The term …

Novel Numerical Approaches For The Resolution Of Direct And Inverse Heat Transfer Problems, Gregory Evan Osborne

Doctoral Dissertations

This dissertation describes an innovative and robust global time approach which has been developed for the resolution of direct and inverse problems, specifically in the disciplines of radiation and conduction heat transfer.

Direct problems are generally well-posed and readily lend themselves to standard and well-defined mathematical solution techniques. Inverse problems differ in the fact that they tend to be ill-posed in the sense of Hadamard, i.e., small perturbations in the input data can produce large variations and instabilities in the output. The stability problem is exacerbated by the use of discrete experimental data which may be subject to substantial measurement …

Flow Structures In An Enclosed Simplified Full Scale Under-Hood Engine Compartment During Steady State Operation, Chin Hoong Leong

Masters Theses

An experimental study of flow structures in an enclosed simplified full scale under-hood engine compartment will be conducted during steady state operation using whole field velocity measuring technique. 2D Particle Image Velocimetry (PIV) is planned for multiple cross sections in the test volume. Emphasis is given on understanding the flow structures of the 3D under-hood flow using multiple 2D PIV measurements. A recent study conducted on the engine compartment only consists of three 2D PIV measurement cross sections that sufficiently display 2D flow behavior at specific regions. Therefore, a detailed 3D flow mapping in the enclosure on various cross sections …

Estimation Of Surface Temperature And Heat Flux Using Embedded Thermocouples, Jeffrey Daniel King

Masters Theses

This thesis investigates several new methods for estimating surface temperature and heat flux based on thermocouples embedded within the interior of a test article. The test apparatus was a Mach 2 axisymmetric rocket nozzle with probes embedded at depths of 1/8” and 1/4” from the inner surface of the nozzle at the throat and exit locations. Three methods for numerically estimating temperature and heat flux at the surface of the nozzle were considered: a one-thermocouple slab-coordinate method, a two-thermocouple slabcoordinate method, and a finite-element analysis (FEA) based on a one-dimensional cylindrical coordinate method. Comparisons between the methods, as well as …

Virtual Modeling And Verification Of Air-Ride Truck Seat Using Multibody Dynamics For Whole Body Vibration Evaluation, Devdutt Nandkishore Shende

Masters Theses

To aid the tuning and optimization of the truck seat design to specific trucks and road profiles during the design phase, this study presents the development and validation of a virtual seat model. This study also assess the utility of the model for whole body vibrations evaluation.

The virtual dynamic seat model was developed in MSC. ADAMS/VIEW. The critical elements like the suspension mechanism, the airspring, dampers and seat cushion were modeled using tested data. To validate the performance of the virtual model, prototype tests were performed using the MTS 6-axis simulator. The modeling process was targeted to achieve a …

A Practical Guideline For Establishing Non-Return Valve Specification And Performance Criteria, Eric W. Dawkins

Masters Theses

The non-return valve has been a standard piece of equipment in the injection molding industry since the reciprocating screw was developed. Most molders understand the role of the non-return valve in the molding process. But few understand the functional problems of the non-return valve. Because of this, the non-return valve has been considered a nuisance item for injection molders.

Wear of the non-return valve is another problem that molders are faced with. The factors contributing toward wear are not entirely understood. Material, temperatures, hours and machine size, etc., all effect the life of a valve. Consequently, most worn valves are …

Design Of An Active Orthotic Device For Joint Management., Steven Clayton Anderson

Electronic Theses and Dissertations

Existing treatment programs and procedures are incapable of addressing the complications encountered with patients who experience spasticity and hypertonia related joint contractures. Current passive therapy procedures and devices are only capable of managing the extent of joint contractures on patients with chronic and acute onset severe neurological disorders. The project was conceived as a means to develop an active device that is capable of adapting to the state of the joint to mange the extent of contractures and to permit consideration for the prevalence of spastic activity episodes and hypertonia. The project focused on the design of the physical prototype …

Inverse Kinematics Based On Fuzzy Logic And Neural Networks For The Wam-Titan Ii Teleoperation System, Joong-Kyoo Park

Masters Theses

The inverse kinematic problem is crucial for robotics. In this paper, a solution algorithm is presented using artificial intelligence to improve the pseudo-inverse Jacobian calculation for the 7-DOF Whole Arm Manipulator (WAM) and 6-DOF Titan II teleoperation system. An investigation of the inverse kinematics based on fuzzy logic and artificial neural networks for the teleoperation system was undertaken. Various methods such as Adaptive Neural-Fuzzy Inference System (ANFIS), Genetic Algorithms (GA), Multilayer Perceptrons (MLP) Feedforward Networks, Radial Basis Function Networks (RBF) and Generalized Regression Neural Networks (GRNN) were tested and simulated using MATLAB. Each method for identification of the pseudo-inverse problem …

Analysis Of Electrical Activity Of The Core Muscles Exposed To Whole-Body Vibrations While Driving A Tractor Trailer Using Electromyography Device, Harini Mangavelli

Masters Theses

Lower back disorders are observed to be the most significant problem for most of the industrial workers who operate commercial vehicles. A person sitting can have 40% higher load on the lumbar spine than when standing. Human core muscles related to spinal movement respond to rapid potential motions related to external acceleration inputs of vibration in order to control body posture, the increased muscle tension can result in muscle fatigue. The over use of muscles, vibration exposure combined with dehydration of spine and long term seating can lead to lower back pain and axial discomfort to the drivers. Electromyography (EMG) …

Numerical Study Of Fully Developed Laminar And Turbulent Flow Through Microchannels With Longitudinal Microstructures, Kevin B. Jeffs

Theses and Dissertations

Due to the increase of application in a number of emerging technologies, a growing amount of research has focused on the reduction of drag in microfluidic transport. A novel approach reported in the recent literature is to fabricate micro-ribs and cavities in the channel wall that are then treated with a hydrophobic coating. Such surfaces have been termed super- or ultrahydrophobic and the contact area between the flowing liquid and the solid wall is greatly reduced. Further, due to the scale of the micropatterned structures, the liquid is unable to wet the cavity and a liquid meniscus is formed between …

Planteamiento Y Programación De Trayectorias Para Labores De Ensamblaje Con El Robot Hidráulico De La Universidad De La Salle, Jairo José Barrera Pinto, Edgar Leonardo Calcetero Tintín

Ingeniería en Automatización

No abstract provided.

Integrated Piezoresistive Sensing For Feedback Control Of Compliant Mems, Robert K. Messenger

Theses and Dissertations

Feedback control of MEMS devices has the potential to significantly improve device performance and reliability. One of the main obstacles to its broader use is the small number of on-chip sensing options available to MEMS designers. A method of using integrated piezoresistive sensing is proposed and demonstrated as another option. Integrated piezoresistive sensing utilizes the inherent piezoresistive property of polycrystalline silicon from which many MEMS devices are fabricated. As compliant MEMS structures flex to perform their functions, their resistance changes. That resistance change can be used to transduce the structures' deflection into an electrical signal. This dissertation addresses three topics …

A Generalized Two-Dimensional Model To Reconstruct The Impact Phase In Automobile Collisions, Regis Agenor David

Theses and Dissertations

Automobile accident reconstruction has been facilitated by the development of computer based modules to allow evaluation of evidence gathered at the accident scenes. Although the computer modules are based in fundamental physical laws, an understanding of these laws by the user is required for proper application of the computer model in a given accident scenario. Vehicle collision analysis techniques generally separate the collision into three phases: pre-impact, impact, and post impact. The intent of the research is to provide a generalized model to reconstruct two dimensional impact problems in the area of accident reconstruction. There are currently two modeling techniques …

Simulación Y Diseño De Un Mecanismo Automático Para Desplazamiento De Piezas En El Área De Pre-Tratamiento Químico De Partes Metálicas, Luis Carlos Romero Bonilla, Rodrigo Quiroga Contreras

Ingeniería en Automatización

No abstract provided.

Máquina Semiautomática Para Dosificado Y Empaque De Líquidos En Bolsa, Juan Carlos Vizcaino Aponte

Ingeniería en Automatización

Sistema semiautomático de dosificado y empaque en el cual el usuario cuenta con el tubo (bolsa) de empaque y necesita dosificar, empacar, sellar y cortar la dosis necesaria. Alimenta un tanque ubicado en la parte superior de la maquina por medio de bombeo de un tanque mas grande que abastece de material a la maquina. Luego por medio de una jeringa industrial se succiona la cantidad deseada de empaque para luego dosificarla por un tubo que dirige el liquido a la zona de empaque en donde un sistema de selle por medio de mordazas realiza la acción de sellar y …

Simulation And Fabrication Of Three Novel Micromechanical Sensors, Yanqing Lu

Doctoral Dissertations

This work focuses on the simulation, fabrication and characterization of novel microdevices for chemical and biological sensors for improved sensitivity, enhanced performance and applicability. Specifically, microbridge and microcoil sensors have been fabricated via advanced microfabrication technologies. Due to the potential application in chemical and biological sensing, the growth of gold and platinum nanowires during an electrolysis process have also been investigated.

A microbridge can be considered as the head-to-head fusion of two cantilevers and the middle of the bridge would deform in a way similar to a microcantilever. The microbridge sensing device is more stable than the microcantilever, especially in …

Kaizen Effectiveness And Execution Strategies, David Buye

Culminating Projects in Mechanical and Manufacturing Engineering

As technology and the educational levels of employees increase, companies typically benefit from the new applications or methodologies introduced into their organizations. A common constraint that causes many companies to lag behind the competition is the amount of waste within their organizations. Companies can have the best technologies and ideas, but if the way that they implement them is not efficient, they will continue to throw money away even if they do not realize it.

Lean manufacturing has been the answer for many companies that have experienced a history of waste. This paper discusses the broad picture of lean practices …

Principles, Functions, And Concepts For Compliant Mechanically Reactive Armor Elements, Cameron S. Andersen

Theses and Dissertations

There exists a great need for armor systems with greater mass efficiencies and ballistic limits. This thesis explores the development of a new field of armor capable of satisfying the increased demand for modern armor: Mechanically Reactive Armor or MRA. More specifically, the thesis focuses on Compliant MRA or CMRA. From the physics governing projectile-armor interactions, principles governing successful design of MRA are identified and presented. These principles or design approaches focus primarily on rejecting, minimizing, or absorbing the incoming projectile's kinetic energy. After identifying these principles, the specific mechanical functions required by the principles are isolated. These functions represent …

Numerical Simulation Of Vortex Generating Jets In Zero And Adverse Pressure Gradients, Curtis Lynn Memory

Theses and Dissertations

Numerical simulations of particle image velocimetry (PIV) experiments conducted with vortex generating jets (VGJs) on a flat plate, at a Reynolds number based on plate length of 50,000, were performed for three flow conditions using a time-accurate hybrid Navier-Stokes solver. Time-averaged steady blowing of angled jets, subjected to a zero pressure gradient, yielded excellent agreement with the PIV data in terms of vortex formation and strength. Observed flow features include primary and secondary vortices, where the primary vortex eventually dominates the downstream region. A shell wall structure, created by smaller vortical structures surrounding the developing vortices, was also observed. A …

Diseño De Un Sistema De Alimentación Y Retiro De Material En La Sección De Prehormado De Copas Para Brassieres, Diego Fernando Ruiz Gomez

Ingeniería en Automatización

En el proceso de la elaboración de insumos para corsetería, la elaboración de las copas de los brassieres, permitieron implementar un nuevo sistema de fabricación de este producto en la sección de prehormado, donde se incrementara la eficiencia, la calidad, y la utilización de este recurso, en donde se estudiaron y se tuvieron en cuenta diferentes parámetros de diseño como lo son: construcción de la estructura, la seguridad industrial, la versatilidad de la máquina, entre otros. Se mostrara además la obtención y los diferentes análisis y cálculos de los sistemas mecánicos, eléctricos, neumáticos y demás sistemas que intervienen en el …

Diseño De Un Control De Variables Para La Línea De Freído De Papa Frita De La Empresa Comestibles Ricos Ltda, Julieth Milena Quevedo Ramírez

Ingeniería en Automatización

No abstract provided.

Validation Of The Afit Small Scale Combustion Facility And Oh Laser-Induced Fluorescence Of An Atmospheric Laminar Premiext Ed Flame, Stephen J. Koether

Theses and Dissertations

Construction in the AFIT combustion facility is complete and the objective of this report is to explain the steps taken to make the laboratory operational. The infinite radius Ultra-Compact Combustor (UCC) sectional model has been delivered and is fully installed with all fuel, air and instrument lines. Every major system in the lab has been tested and is functioning properly. Laboratory operating procedure has been established to ensure both safety and continuity in experimental results. Finally, the lab has been certified through official safety channels and combustion experiments are underway. The unique capability of the AFIT combustion laboratory is the …

Conceptual Mems Devices For A Redeployable Antenna, Virginia Miller

Theses and Dissertations

Micro-Electro-Mechanical Systems (MEMS) are becoming an integral part of our lives through a wide range of applications, including MEMS accelerators for air bag deployment in vehicles, micromirrors in projection devices, and various sensors for chemical/biological applications. MEMS are a key aspect of ever-increasing significance in a myriad of commercial and military applications. Because of this importance, this thesis utilizes MEMS devices that can deploy and retract an antenna suitably sized for placement on an insect or microrobot for communication purposes. A target monopole antenna with a length of 1 mm was used as a test metric. From this requirement, several …

Adaptive Quaternion Control For A Miniature Tailsitter Uav, Nathan B. Knoebel

Theses and Dissertations

The miniature tailsitter is a unique aircraft with inherent advantages over typical unmanned aerial vehicles. With the capabilities of both hover and level flight, these small, portable systems can produce efficient maneuvers for enhanced surveillance and autonomy with little threat to surroundings and the system itself. Such vehicles are accompanied with control challenges due to the two different flight regimes. Problems with the conventional attitude representation arise in estimation and control as the system departs from level flight conditions. Furthermore, changing dynamics and limitations in modeling and sensing give rise to significant attitude control design challenges. Restrictions in computation also …

Design And Fabrication Of Out-Of-Plane Silicon Microneedles With Integrated Hydrophobic Microchannels, Michael S. Diehl

Theses and Dissertations

Microfabricated needles have the potential for inexpensive drug delivery without pain. The ability to deliver medication painlessly to patients will someday be not just hoped for but expected by the general public. The commercialization of this technology will also lead to other valuable technologies, such as systems that continually monitor and control insulin or other drugs in diabetic patients. This research presents fabrication procedures developed to produce pyramidal-shaped microneedles with microchannels that will allow for fluid delivery. The microchannels are etched into the substrate surface of a [100] silicon wafer using inductively coupled plasma etching. After the channel etch a …

Development Of An Integrated Opto-Electric Biosensor To Dynamically Examine Cytometric Proliferation And Cytotoxicity, Chang Kyoung Choi

Doctoral Dissertations

My doctoral research has focused on the development of microscale optical techniques for examining micro/bio fluidics. Preliminary work measured the velocity field in a microchannel, by optical slicing, using Confocal Laser Scanning Microscopy (CLSM). Next, Optical Serial Sectioning Microscopy (OSSM) was applied to examine thermometry by detecting the free Brownian motion of nano-particles suspended in mediums at different temperatures. An extension of this work used objective-based Total Internal Reflection Fluorescence Microscopy (TIRFM) to examine the hindered Brownian motion of nano-particles that were very close to a solid surface (within 1 mm).

An optically transparent and electrically conductive Indium Tin Oxide …