Mechanical Engineering Commons^™

Transient Small Wind Turbine Tower Structural Analysis With Coupled Rotor Dynamic Interaction, George R. Katsanis

Master's Theses

Structural dynamics is at the center of wind turbine tower design - excessive vibrations can be caused by a wide range of environmental and mechanical sources and can lead to reduced component life due to fatigue, noise, and impaired public perception of system integrity. Furthermore, periodic turbulent wind conditions can cause system resonance resulting in significantly increased structural loads. Structural vibration issues may become exacerbated in small wind applications where the analytical and experimental resources for system verification and optimization are scarce. This study combines several structural analysis techniques and packages them into a novel and integrated form that can …

Novel Approach To Junctional Bleeding: Tourniquet Device Proposal For Battlefield Hemorrhage Control, Kyle W. Cabaniss

Master's Theses

This study investigated possible solutions to the current wartime problem of junctional hemorrhaging, or massive traumatic hemorrhaging in non-tourinquetable areas such as the neck, groin, or armpit. Junctional hemorrhaging has been identified as a major contributor to potentially survivable deaths seen on the battlefield today and therefore is a priority for the U.S. armed and coalition forces (Kragh et al., 2011a; Bozeman, 2011). Common tourniquets today are standard issue and carried by soldiers in the military, but are limited to distal extremity trauma. As the battlefield has changes however, trauma has transformed from commonly seen gunshot wounds to more extreme …

Material Characterization And The Effects Of Moisture And Drying On Injection Molded Torlon 5030, Michael R. Di Re

Master's Theses

The effects of water absorption and drying were studied on injection molded Torlon 5030, a high performance thermoplastic fabricated by Solvay Specialty Polymers. Torlon 5030 contains 30% by weight glass fibers in a polyamide-imide base resin. The objective behind this work was to test and better define relevant properties for industrial applications using this material. While the material design guide offers information on many mechanical properties including tensile, fatigue, and creep data; there is little to no publicly published data on the effects of water absorption and any subsequent drying of Torlon 5030. Blistering was also studied. With exposure to …

The Effect Of Sensor Mass, Sensor Location, And Delamination Location Of Different Composite Structures Under Dynamic Loading, Albert Darien Liu

Master's Theses

This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, …

A Finite Difference Implementation Of Phase Field Theory, Nicholas W. Oren

Master's Theses

Computationally handling cracks generally results in numerically unstable results. Specifically handling the infinite stresses at the crack tip as well as the abrupt change from virgin material to failed material creates numerical instabilities. This project seeks to determine if phase field physics theory, particularly the physics based modification developed by B. N. Cassenti, can be appropriately applied to cracks. Phase field theory introduces an additional state variable, the phase of the material. The phase represents the level of failure (by cracking), and diffuses the failure along a crack by specified equations. The modification, based on a variational principle, was tested …

Design And Simulation Of Passive Thermal Management System For Lithium-Ion Battery Packs On An Unmanned Ground Vehicle, Kevin Kenneth Parsons

Master's Theses

The transient thermal response of a 15-cell, 48 volt, lithium-ion battery pack for an unmanned ground vehicle was simulated with ANSYS Fluent. Heat generation rates and specific heat capacity of a single cell were experimentally measured and used as input to the thermal model. A heat generation load was applied to each battery and natural convection film boundary conditions were applied to the exterior of the enclosure. The buoyancy-driven natural convection inside the enclosure was modeled along with the radiation heat transfer between internal components. The maximum temperature of the batteries reached 65.6 °C after 630 seconds of usage …

Finite Element Model Updating For Rotary Machinery, Nathalie Gotin

Master's Theses

The main approach of this thesis was to develop a mathematical model that represents a rotary machine. Experimental data was used to define a finite element model (FEM). In order to obtain the experimental data, the rotary machine had to be balanced. An impact hammer test made it possible to obtain frequency response functions (FRF). The frequency response functions were curvefitted in order to obtain the mode shapes and natural frequencies.

Mathematical models have been created with ABAQUS and Matlab. For the Matlab Model the assumption has been made that the rotor machine consists of a specific number of beam …

The Role Of Transport Phenomena In The Direct Oxidation Of Solid Fuels, Charles J. Banas

Master's Theses

Direct carbon fuel cells have shown promise for stationary power generation by utilizing the direct oxidation of a solid carbon fuel source at the anode. In laboratory settings, researchers have reported up to 300mA/cm2 of current density from these cells types which suffer from mass transport losses. This paper studies the surface properties of the solid fuel source, and describes the process of CO2 evolution through an analogy to pool boiling. In nucleate boiling (a subset of pool boiling) vapor bubbles grow from nucleation sites where gas are trapped in micro-cavities on the surface. Carbon surfaces possess these same features, …

Efficient Characterization Of Structural Dynamic Responses Under Uncertainties: From Order-Reduced Simulation To Data-Driven Emulation, Zeping Xia

Master's Theses

The efficiency of sampling remains as one of the major challenges for uncertainty analysis in structural dynamics. In the context of numerical experiments, this difficulty primarily lies in the fact that every single run of a numerical model, which usually is of large scale in modern engineering practice, would be expensive in terms of CPU times and memories. Nonetheless, understanding and predicting dynamic characteristics of structural systems with uncertainties is important for structural design, assessment and control. In order to develop fast and economical sampling techniques for characterizing structural dynamics, we explored two categories of methods from two opposite direction: …

Static Balancing Of The Cal Poly Wind Turbine Rotor, Derek Simon

Master's Theses

The balancing of a wind turbine rotor is a crucial step affecting the machine’s performance, reliability, and safety, as it directly impacts the dynamic loads on the entire structure.

A rotor can be balanced either statically or dynamically. A method of rotor balancing was developed that achieves both the simplicity of static balancing and the accuracy of dynamic balancing. This method is best suited, but not limited, to hollow composite blades of any size. The method starts by quantifying the mass and center of gravity of each blade. A dynamic calculation is performed to determine the theoretical shaking force on …

Phase-Resolved Characterization Of Conical Turbulent Premixed Flames: An Investigation Of Forced Blowoff Dynamics, Sayan Biswas

Master's Theses

Flame dynamics of a bluff body stabilized turbulent premixed flame as it approaches lean blowoff is of interest for practical applications. It is also important to understand the flame behavior under harmonic flow perturbations as it may occur due to acoustically unstable operation of compact combustors. In this study, a harmonically excited conical flame was studied to determine its behavior under strong burning and near blowoff conditions. Chemiluminescence imaging was employed using a Photron high speed camera to characterize the phase resolved flame characteristics for a range of excitation frequencies from 50 to 400 Hz in confined and unconfined geometries. …

Fabrication And Characterization Of Torsional Micro-Hinge Structures, Mike Madrid Marrujo

Master's Theses

ABSTRACT

Fabrication and Characterization of Torsional Micro-Hinge Structures

Mike Marrujo

There are many electronic devices that operate on the micrometer-scale such as Digital Micro-Mirror Devices (DMD). Micro actuators are a common type of DMD that employ a diaphragm supported by torsional hinges, which deform during actuation and are critical for the devices to have high stability and reliability. The stress developed within the hinge during actuation controls how the actuator will respond to the actuating force. Electrostatically driven micro actuators observe to have a fully recoverable non-linear viscoelastic response. The device consists of a micro-hinge which is suspended by two …

Viscoelastic Anisotropic Finite Element Mixture Model Of Articular Cartilage Using Viscoelastic Collagen Fibers And Validation With Stress Relaxation Data, Matthew Alexander Griebel

Master's Theses

Experimental results show that collagen fibers exhibit stress relaxation under tension and a highly anisotropic distribution. To further develop the earlier model of Stender [1], the collagen constituent was updated to reflect its intrinsic viscoelasticity and anisotropic distribution, and integrated with an existing mixture model with glycosaminoglycans and ground substance matrix. A two-term Prony series expansion of the quasi-linear viscoelastic model was chosen to model the viscoelastic properties of the collagen fibers. Material parameters were determined by using the simplex method to minimize the sum of squared errors between model results and experimental stress relaxation data of tissue in tension. …

A Model Predictive Control Approach To Roll Stability Of A Scaled Crash Avoidance Vehicle, Nikola John Linn Noxon

Master's Theses

In this paper, a roll stability controller (RSC) is presented based on an eight degree of freedom dynamic vehicle model. The controller is designed for and tested on a scaled vehicle performing obstacle avoidance maneuvers on a populated test track. A rapidly-exploring random tree (RRT) algorithm is used for the vehicle to execute a trajectory around an obstacle, and examines the geographic, non-homonymic, and dynamic constraints to maneuver around the obstacle. A model predictive controller (MPC) uses information about the vehicle state and, based on a weighted performance measure, generates an optimal trajectory around the obstacle. The RSC uses the …

An Investigation Of Damage Arrestment Devices On Carbon Fiber Sandwich Specimens Under Dynamic Loading, Gabriel Sabino Sanchez

Master's Theses

This research studies the effects of a damage arrestment device embedded between a carbon fiber facesheet and foam core to find whether there is an increase in the structural integrity of the sandwich composites. Experimental and theoretical finite element analyses are implemented for two different composite sandwich geometries; plates and beams. Each structure consisted of the same loading criteria and was restricted to the same vibration fixture during the experiment. An accelerometer was placed on the composite plate to record the amplitude and the natural frequencies of the composite structure. Each composite specimen is then fixed to the surface of …

Vibration Health Monitoring Of Gears, Markus Josef Scherer

Master's Theses

Monitoring the health of vibrating gears is important to ensure proper operation especially in potentially life-threatening structures, such as helicopters, nuclear power plants, and uninterruptible power supply transitions in hospitals. The most common monitoring technique is casing mounted accelerometers to measure vibration. In contrast, during the last few years acoustic monitoring techniques have also provided a few diagnostic methods for gear failure. Current diagnostic methods to indicate improper gear behavior use either existing vibration data, recorded from defective gear systems, or modern dynamic models predicting gear failure behavior.

This thesis uses dynamic models to indicate, predict, and diagnose healthy and …

Prediction Of Articular Cartilage Remodeling During Dynamic Compression With A Finite Element Model, Kevin Akira Yamauchi

Master's Theses

First, an in vitro growth experiment was performed to test the hypothesis that applying dynamic unconfined compression during culture produces het- erogeneous remodeling in newborn bovine articular cartilage explants. Het- erogeneous measures of cartilage microstructure were obtained by biochemical assays and quantified polarized light microscopy. Significant differences were measured between the GAG content in the inner and outer portions of the sam- ples stimulated with dynamic unconfined compression. The COL fiber network was found to be more highly aligned in the inner portion of the sample than in the peripheral region.

Next, a poroelastic finite element model with a remodeling …

Small-Scale Solar Central Receiver System Design And Analysis, Daniel Murray

Master's Theses

This thesis develops an analytical model of a small-scale solar central receiver power plant located at the California Polytechnic State University in San Luis Obispo, California at 35.28° N, 120.66° W. The model is used to analyze typical energy output at any time during the year. The power plant is designed to produce an output of 100 kW electrical power, and is supplemented by the combustion of natural gas. Methodologies for determining the proper size and layout of heliostats, optimal tower height, receiver size, and turbine engine selection are developed. In this specific design, solar shares of up to 73.2% …

Finite Element Modeling Of Ballistic Impact On A Glass Fiber Composite Armor, Dan M. Davis

Master's Theses

Finite Element Modeling of Ballistic Impact on a Glass Fiber Composite Armor

Dan Davis

Experiments measuring the ballistic performance of a commercially available fiberglass armor plate were used to guide the development of constitutive laws for a finite element model of the impact. The test samples are commercially available armor panels, made from E-glass fiber reinforced polyester rated to NIJ level III. Quasi-static tensile tests were used to establish material properties of the test panels. These properties were then used to create models in the explicit finite element code LSDYNA.

Ballistic impact testing of the panels was conducted using a …

Agent-Based Modeling Of Emergency Building Evacuation, Vi Q. Ha

Master's Theses

Panic during emergency building evacuation can cause crowd stampede, resulting in serious injuries and casualties. Agent-based methods have been successfully employed to investigate the collective human behavior during emergency evacuation in cases where the configurational space is extremely simple - usually one rectangular room - but not in evacuations of multi-room or multi-floor buildings. This implies that the effect of the complexity of building architecture on the collective behavior of the agents during evacuation has not been fully investigated. Here, we employ a system of self-moving particles whose motion is governed by the social-force model to investigate the effect of …

Advanced Design Optimization For Composite Structure: Stress Reduction, Weight Decrease And Manufacturing Cost Savings, Shayan Ahmadian

Master's Theses

An injection moldable chopped fiber composite actuator with detailed drawing and tolerances was designed within one year. A vendor was selected and a quote for injection molding tooling cost for production was obtained and the first prototype was built in addition of six months. The risks are identified and material characterization tests are proposed.

The objective of this project was redesigning an aluminum made actuator with a continuous fiber composite for weight saving purposes. After searching the literature and consulting with experts in the field it was concluded that manufacturing costs associated with continuous fiber composite are 3 times as …

An Investigation Of Fraxinus Americana Branch Sway Using A 3 Dimensional Motion Capture System, Anna T. Campiformio

Master's Theses

Abstract

Wind is a dominant abiotic factor that a tree experiences throughout its lifetime and can cause severe tree damage, resulting in risk of injury to humans, and economic and ecological losses. It is thought that trees develop structural properties and architectures that help withstand loading conditions by dissipating wind energy through damping mechanisms. The role of branch motion in reducing potential dangerous wind loads has been the focus of relatively few studies. Even fewer studies have examined tree sway response to natural wind loaded conditions. In this investigation, branch frequencies were calculated for three Fraxinus americana using a three-dimensional …

Latent Heat Thermal Energy Storage With Embedded Heat Pipes For Concentrating Solar Power Applications, Christopher Robak

Master's Theses

An innovative, novel concept of combining heat pipes with latent heat thermal energy storage (LHTES) for concentrating solar power (CSP) applications is explored. The low thermal conductivity of phase change materials (PCMs) used in LHTES presents a design challenge due to slow heat transfer rates during heating and cooling of the material. Heat pipes act to decrease the thermal resistance in the PCM, increasing the overall heat transfer rate sufficiently for use in CSP. First, a laboratory scale experiment is presented to validate the concept of using heat pipes in LHTES to reduce thermal resistance in PCM. A commercial scale …

Combustion Simulations Using Graphic Processing Units, Mingjie Wang

Master's Theses

Graphic processing units (GPUs) are powerful graphics engines featuring high levels of parallelism and extreme memory bandwidth, which constitute a powerful computing platform to solve complex problems involving chemically reacting flows. In the present study, computer programs for combustion simulations with detailed chemical kinetic mechanisms were compiled in the Compute Unified Device Architecture (CUDA) language for NVIDIA GPU architecture. Ignition processes were simulated under constant pressure and constant volume conditions using an explicit 4^th order Runge-Kutta algorithm for time integration. Sufficiently small time steps were identified with time scale analysis to ensure the integration stability. The program was validated …

Mechanical Integration Of A Versatile Air Suspension Into A Powered Wheelchair, Joel Michael Steinkraus

Master's Theses

Mechanical Integration of a Versatile Air Suspension into a Powered Wheelchair

Joel Steinkraus

It is undeniable that the vibration environment created by prolonged exposure to wheelchair use can cause discomfort for the rider and put him/her at risk of developing more severe medical conditions. While more research must be done to accurately quantify what constitues a harmful vibration environment, improved vibraiton isolation is an essential step. In order to incorporate structurally sound and effetive air suspension systems into motorized wheelchairs, a support structure is necessary. An after market wheelchair suspension system was designed, modeled, built and tested. Approximately 18 inches …

The Design And Fabrication Of A Microfluidic Reactor For Synthesis Of Cadmium Selenide Quantum Dots Using Silicon And Glass Substrates, Peter Robert Gonsalves

Master's Theses

A microfluidic reactor for synthesizing cadmium selenide (CdSe) quantum dots (QDs) was synthesized out of a silicon wafer and Pyrex glass. Microfabrication techniques were used to etch channels into the silicon wafer. Holes were wet-drilled into the Pyrex glass using a diamond-tip drill bit. The Pyrex wafer was anodically bonded to the etched silicon wafer to enclose the microfluidic reactor. Conditions for anodic bonding were created by exposing the stacked substrates to 300V at ~350oC under 5.46N of force. A syringe containing a room temperature CdSe solution was interfaced to the microfluidic reactor by using Poly (dimethylsiloxane) (PDMS) as an …

Dynamic Test Scheduling In Hardware-In-The-Loop Simulation Of Commercial Vehicles, Tenil Cletus

Master's Theses

Modern day commercial vehicles are controlled by various Electronic Control Units (ECU). They are not only tested as single units, but also by networking them in Controlled Area Network bus (CAN) to form a complete electrical control system. This is achieved using Hardware In the Loop (HIL) Integration Lab. In HIL, the electrical system is connected to a real time mathematical model of the vehicle plus it’s environment so as to form a loop.

Testing functionality of the electrical system begins by defining functional tests. An example would be testing cruise control activation. Executing each test is made possible by …

Predicting The Acoustic Response Of The Golf Club & Ball Impact Using Finite Elements And The Boundary Element Method, Scott Henry Moreira

Master's Theses

An improved and repeatable method for meshing golf club heads using finite elements in TrueGrid® was developed. Using solid brick elements through the thickness of the club head instead of shell elements better represents the many thickness variations throughout each section of a club head. This method also results in a high quality mesh at the center of the club head sections while still maintaining high quality at the edges. A simulation procedure was also developed to predict the acoustic pressure at a designated point in an acoustic medium of a golf club and ball impact using the BEM and …

Evaluation Of Cathode Materials For Low Temperature (500-700c) Solid Oxide Fuel Cells, Alexander M. Lassman

Master's Theses

Solid oxide fuel cells (SOFC) have gained a great deal of interest, due to their potential for high efficiency power generation and ability to utilize hydrogen fuel, as well as various hydrocarbon-based fuels. A recent trend in SOFC development has been towards lower operating temperatures (500-700°C), which can substantially reduce the cost and complexity of the system. This thesis presents an investigation into state of the art Ba- and La- based cathode materials for use in low temperature (500-700°C) solid oxide fuel cells.

Synthesis of A-site deficient [A=0.97] Ba_0.5Sr_0.5Co_0.8Fe_0.2O₃ (BSCF) was …

California Polytechnic State University Wind Resource Assessment, Jason Allan Smith

Master's Theses

Wind resource assessment at California Polytechnic State University shows there is potential for wind power generation on Cal Poly land. A computational fluid dynamics model based on wind data collected from a campus maintained meteorological tower on Escuela Ranch approximately 5 miles northwest of campus suggests there are areas of Cal Poly land with an IEC Class III wind resource at a height of 80 meters above ground. In addition during the daytime when the campus uses the most energy there are large portions of land with annual average daytime wind speeds above 6.9m/s. These areas have been identified by …