The Study Of Frequency-Scan Photothermal Reflectance Technique For Thermal Diffusivity Measurement, 2015 Utah State University
The Study Of Frequency-Scan Photothermal Reflectance Technique For Thermal Diffusivity Measurement, Zilong Hua, Heng Ban, David H. Hurley
Mechanical and Aerospace Engineering Faculty Publications
A frequency scan photothermal reflectance technique to measure thermal diffusivity of bulk samples is studied in this manuscript. Similar to general photothermal reflectance methods, an intensity-modulated heating laser and a constant intensity probe laser are used to determine the surface temperature response under sinusoidal heating. The approach involves fixing the distance between the heating and probe laser spots, recording the phase lag of reflected probe laser intensity with respect to the heating laser frequency modulation, and extracting thermal diffusivity using the phase lag–(frequency)1/2 relation. The experimental validation is performed on three samples (SiO2, CaF2, and …
Engineered Surface Properties Of Porous Tungsten From Cryogenic Machining, 2015 University of Kentucky
Engineered Surface Properties Of Porous Tungsten From Cryogenic Machining, Julius M. Schoop
Theses and Dissertations--Chemical and Materials Engineering
Porous tungsten is used to manufacture dispenser cathodes due to it refractory properties. Surface porosity is critical to functional performance of dispenser cathodes because it allows for an impregnated ceramic compound to migrate to the emitting surface, lowering its work function. Likewise, surface roughness is important because it is necessary to ensure uniform wetting of the molten impregnate during high temperature service. Current industry practice to achieve surface roughness and surface porosity requirements involves the use of a plastic infiltrant during machining. After machining, the infiltrant is baked and the cathode pellet is impregnated. In this context, cryogenic machining is …
Effect Of Impact Damage On Compression-Compression Fatigue Behavior Of Sandwich Composites, 2015 Wayne State University
Effect Of Impact Damage On Compression-Compression Fatigue Behavior Of Sandwich Composites, Ali M. Al-Sharif
Wayne State University Dissertations
The aim of this research work was to investigate the effect of impact damage on in-plane buckling and compression-compression fatigue behavior for a new sandwich structure made from E-glass/epoxy face sheets over end-grain balsa wood core. Low velocity impact tests were carried out using a drop-weight impact tower by impacting the sandwich beam at the center with energy level slightly higher than threshold energy level of 8.8 J. Edge-wise compression static tests were conducted for impacted and non-impacted samples to address energy absorption characteristics of these composites. Analytical and experimental investigations were carried out to measure critical buckling loads and …
Quantification Of Auto-Ignition In Diesel Engines, 2015 Wayne State University
Quantification Of Auto-Ignition In Diesel Engines, Umashankar M. Joshi
Wayne State University Dissertations
Efforts have been made previously by researchers to quantify the auto-ignition quality of fuels by calculating global activation energy using Arrhenius plots with data measured for the ignition delay period (ID). Large variation in the activation energy of fuels has been observed even for fuels with closer CN values. More recently, the activation energy values obtained by Kook et al in (2005) on an optical engine do not agree with data obtained in an identical metallic engine by Jayakumar using fuels of same CN.
The disparity in their results can be attributed to the differences in ignition delay (ID) and …
Methodology For Validating Multi-Dimensional Engine Combustion Models And Fuel Surrogates Using An Optically Accessible Compression Ignition Engine, 2015 Wayne State University
Methodology For Validating Multi-Dimensional Engine Combustion Models And Fuel Surrogates Using An Optically Accessible Compression Ignition Engine, Xin Yu
Wayne State University Dissertations
In response to increasingly stringent engine emissions regulation, three dimensional in-cylinder combustion modeling is increasingly being used as a tool to optimize the combustion process and reduce the cost of experimental testing. Due to the complexity of the physical and chemical interactions involved in the in-cylinder combustion process, the engine combustion model consists of numerous sub-models developed under pre-defined initial and boundary conditions requiring further model calibration depending on different engine applications. Fuel surrogates, one of those sub-models developed for different combustion applications, may not capture all the behavior when applied to the varying temperature-pressure conditions present in a compression …
Edge Fracture Prediction Of Dual Phase Steels With Consideration Of Microstructures, 2015 Wayne State University
Edge Fracture Prediction Of Dual Phase Steels With Consideration Of Microstructures, Ming Wen
Wayne State University Dissertations
In recent years, Advanced High Strength Steels (AHSS) have been used for the lightweight structural design and manufacturing in automotive industry. This class of sheet metals are prone to edge fracture during stamping production, and the fracture often occurs at much lower strain than that predicted based on the forming limit curves. The uncertainty in predicting edge fracture represents a great challenge in the application of AHSS. This dissertation is focused on the better understanding of edge fracture phenomenon through experimental observation and computer modeling with the consideration of microstructure effect.
In this dissertation, Hole Expansion (HE) test was used …
Spectral Radiation Analysis Of Premixed Oxy-Syngas And Oxy-Methane Flames, 2015 University of Texas at El Paso
Spectral Radiation Analysis Of Premixed Oxy-Syngas And Oxy-Methane Flames, Naznin Jahan Afrose
Open Access Theses & Dissertations
Oxy-fuel combustion has potential to be an impeccable enhancement of current combustion techniques. For a hydrocarbon burning with oxygen the resulting exhaust stream is composed mainly of carbon dioxide and water vapor. This exhaust allows for easier carbon capture and sequestration since the water can be condensed out. Another advantage is the significant reduction of NOx since much of the nitrogen found in air-combustion systems is eliminated. These processes also provide a higher theoretical efficiency which is advantageous. Although beneficial many of the exhaust gas products radiative characteristics are unknown. Motivated by this, this paper focuses on the spectral radiation …
Design And Analysis Of A Novel Latch System Implementing Fiber-Reinforced Composite Materials, 2015 University of Texas at El Paso
Design And Analysis Of A Novel Latch System Implementing Fiber-Reinforced Composite Materials, Francisco Guevara
Open Access Theses & Dissertations
The use of fiber-reinforced composite materials have increased in the last four decades in high technology applications due to their exceptional mechanical properties and low weight. In the automotive industry carbon fiber have become popular exclusively in luxury cars because of its high cost. However, Carbon-glass hybrid composites offer an effective alternative to designers to implement fiber-reinforced composites into several conventional applications without a considerable price increase maintaining most of their mechanical properties. A door latch system is a complex mechanism that is under high loading conditions during car accidents such as side impacts and rollovers. Therefore, the Department of …
Modeling And Preliminary Characterization Of Passive, Wireless Temperature Sensors For Harsh Environment Applications Based On Periodic Structures, 2015 University of Texas at El Paso
Modeling And Preliminary Characterization Of Passive, Wireless Temperature Sensors For Harsh Environment Applications Based On Periodic Structures, Diego Ivan Delfin Manriquez
Open Access Theses & Dissertations
Wireless temperature sensing has attained significant attention in recent years due to the increasing need to develop reliable and affordable sensing solutions for energy conversion systems and other harsh environment applications. The development of next generation sensors for energy production processing parameters, such as temperature and pressure, can result in better performance of the system. Particularly, continuous temperature monitoring in energy conversion systems can result in enhancements such as better system integrity, less pollution and higher thermal efficiencies. However, the conditions experienced in these system components hinder the performance of current solutions due to the presence of semi-conductor materials and …
An Improved Sin-Hyperbolic Constitutive Model For Creep Deformation And Damage, 2015 University of Texas at El Paso
An Improved Sin-Hyperbolic Constitutive Model For Creep Deformation And Damage, Mohammad Shafinul Haque
Open Access Theses & Dissertations
Inspection and maintenance of industrial gas turbines (IGTs) cost millions of dollars. Growing demand of obtaining higher IGT efficiency leads to higher temperature and pressure operating conditions. Long exposure of turbine components at elevated temperature and pressure
makes creep damage critically important to consider during planning, designing and operating conditions. Effective and economic maintenance requires accurate creep deformation, damage
evolution and rupture life prediction information. Creep prediction models are used to determine the state of the turbine components and to schedule the inspection, maintenance and replacement time periods. The more accurate the prediction model, the less is the overall cost …
Design Of A High Intensity Turbulent Combustion System, 2015 University of Texas at El Paso
Design Of A High Intensity Turbulent Combustion System, Mohammad Arif Hossain
Open Access Theses & Dissertations
In order to design next generation gas turbine combustor and rocket engines, a systematic study of flame structure at high intensity turbulent flow is necessary. The fundamental study of turbulent premixed combustion has been a major research concern for decades. The work is focused on the design and development of a high intensity turbulent combustion system which can be operated at compressible (0.3 < M < 0.5), preheated (T0=500K) and premixed conditions in order to investigate the 'Thickened Flame' regime. An air-methane mixture has been used as the fuel for this study. An optically accessible backward-facing step stabilized combustor has been designed for a maximum operating pressure of 6 bar. A grid has been introduced with different blockage ratios (BR = 54%, 61% & 67%) in order to generate turbulence inside the combustor for the experiment. Optical access is provided via quartz windows on three sides of the combustion chamber. Finite Element Analysis (FEA) is done in order to verify the structural integrity of the combustor at rated conditions. In order to increase the inlet temperature of the air, a heating section was designed to use commercially available in-line heaters. Separate cooling subsystems have been designed for chamber cooling and exhaust cooling. The LabVIEW software interface has been selected as the control mechanism for the experimental setup. A 10 kHz Time Resolved Particle Image Velocimetry (TR-PIV) system and a 3 kHz Planer Laser Induced Fluorescence (PLIF) system have been integrated with the system in order to diagnose the flow field and the flame respectively. The primary understanding of the flow field inside the combustor was achieved through the use of Detached Eddy Simulation (DES) by using commercially available software package ANSYS FLUENT. Preliminary validation is done by 10 kHz TR-PIV technique. Both qualitative and quantitative analysis have been done for CFD and experiment. Major flow parameters such as average velocity, fluctuation of velocity, kinetic energy, and turbulent intensity have been calculated for two distinct Reynolds number (Re = 815 & 3500). PIV results are compared with CFD results which show significant agreement with each other.
Thermal Shock Studies On Carbon-Carbon Composites: Experimentation And Analysis, 2015 University of Texas at El Paso
Thermal Shock Studies On Carbon-Carbon Composites: Experimentation And Analysis, Alma Lucia Leanos
Open Access Theses & Dissertations
The oxidation behavior of C/C composites under thermal shock conditions in air is understood and predicted experimentally and by computational efforts. In Chapter. 1, both compressive properties and oxidation behavior of pristine and thermal shock exposed 2D C/C composite specimens were examined. Pristine test specimens were exposed to thermal shock conditions with temperatures ranging from 400°C to 1000°C in an oxidizing environment, followed by compression tests on pristine and thermal shock exposed specimens to obtain their compressive responses.
Similarly, in Chapter. 2, the influence of thermal shock conditions on both, the extent of carbon materials decomposition and the through-thickness compressive …
Novel Classification Of Slow Movement Objects In Urban Traffic Environments Using Wideband Pulse Doppler Radar, 2015 University of Texas at El Paso
Novel Classification Of Slow Movement Objects In Urban Traffic Environments Using Wideband Pulse Doppler Radar, Berta Rodriguez Hervas
Open Access Theses & Dissertations
Every year thousands of people are involved in traffic accidents, some of which are fatal. An important percentage of these fatalities are caused by human error, which could be prevented by increasing the awareness of drivers and the autonomy of vehicles. Since driver assistance systems have the potential to positively impact tens of millions of people, the purpose of this research is to study the micro-Doppler characteristics of vulnerable urban traffic components, i.e. pedestrians and bicyclists, based on information obtained from radar backscatter, and to develop a classification technique that allows automatic target recognition with a vehicle integrated system. For …
Design And Testing Of An Ox/Ch4 Swirl Torch Ignition System, 2015 University of Texas at El Paso
Design And Testing Of An Ox/Ch4 Swirl Torch Ignition System, Gabriel Ricardo Trujillo
Open Access Theses & Dissertations
NASA has renewed its interest in oxygen and methane as propellants for propulsion. Some of the reasons that drive this interest are the ease of storage of liquid methane when compared to hydrogen, the handling safety when compared to hypergols, in-situ resource utilization and its relative clean burning process. This project is part of the larger goal of the Center for Space Exploration Technology Research (cSETR) to better understand the aspects of using this propellants to create future hardware that are specifically optimized for their use. This paper discusses the testing of a previous iteration of the swirl torch igniter …
Development Of A Novel Hybrid Unified Viscoplastic Constitutive Model, 2015 University of Texas at El Paso
Development Of A Novel Hybrid Unified Viscoplastic Constitutive Model, Luis Alejandro Varela Jimenez
Open Access Theses & Dissertations
Gas turbines are now days used in power plants for power generation and for propulsion in the aerospace industry. In these applications gas turbines are exposed to severe temperature and pressure variations during operating cycles. These severe operating conditions exposed the turbineâ??s components to multiple deformation mechanisms which degrade the material and eventually lead to failure of the components. Nickel based and austenitic super alloys are candidate material used for these applications due to its high strength and corrosion resistance at elevated temperatures. At such temperature levels, candidate materials exhibit a rate-dependent or viscoplastic behavior which difficult the prediction or …
Rigidly Foldable Origami Twists, 2015 Brigham Young University - Provo
Rigidly Foldable Origami Twists, Thomas A. Evans, Robert J. Lang, Spencer P. Magleby, Larry L. Howell
Faculty Publications
Rigid foldability is an important characteristic of origami structures that becomes significant with non-paper materials. A rigidly foldable origami tessellation is one where the sectors remain rigid and all deflection occurs at the crease lines. Many rigidly foldable patterns have only one degree of freedom, making them potentially useful for deployable structures. Methods have been developed to construct rigidly foldable origami tessellations using materials with finite thickness based on zero-thickness rigidly foldable patterns. [Tachi 11].
Origami methods have been considered for application in deployable structures such as solar panels [Miura 85] [Zirbel et al. 13] and sterile shrouds [Francis et …
Stress-Limiting Test Structures For Rapid Low-Cost Strength And Stiffness Assessment, 2015 University of South Florida
Stress-Limiting Test Structures For Rapid Low-Cost Strength And Stiffness Assessment, Andrew Katz, Craig P. Lusk, Nathan B. Crane
Faculty Publications
Purpose: Evaluate the use of a simple printed geometry to estimate mechanical properties (elastic modulus, yield strength) with inexpensive test equipment.
Design Methodology/Approach: Test geometry is presented that enables controlled strains with manual deformation and repeatable measurement of vibrational frequencies. This is tested with multiple FDM machines to assess measurement accuracy and repeatability. Printing orientation and some printing parameters are varied to assess the measurement sensitivity.
Findings: The test methods show good correlation with manufacturer material specifications in the X-Y plane and reported elastic strain limits. It is also sensitive to printing orientation and printing parameters.
Research Limitations/Implications: Further work …
Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, 2015 Portland State University
Anisotropy Of The Reynolds Stress Tensor In The Wakes Of Wind Turbine Arrays In Cartesian Arrangements With Counter-Rotating Rotors, Nicholas Hamilton, Raúl Bayoán Cal
Mechanical and Materials Engineering Faculty Publications and Presentations
A 4 × 3 wind turbine array in a Cartesian arrangement was constructed in a wind tunnel setting with four configurations based on the rotational sense of the rotor blades. The fourth row of devices is considered to be in the fully developed turbine canopy for a Cartesian arrangement. Measurements of the flow field were made with stereo particle-image velocimetry immediately upstream and downstream of the selected model turbines. Rotational sense of the turbine blades is evident in the mean spanwise velocity W and the Reynolds shear stress −vw. The flux of kinetic energy is shown to be of greater …
Interface Property Of Collagen And Hydroxyapatite In Bone And Developing Bioinspired Materials, 2015 University of Arkansas, Fayetteville
Interface Property Of Collagen And Hydroxyapatite In Bone And Developing Bioinspired Materials, Clint Paul
Inquiry: The University of Arkansas Undergraduate Research Journal
Bone at the nanoscale consists of type I collagen and hydroxyapatite (HAP). Type I collagen and HAP [Ca10(PO4)6(OH)2] are responsible for most of the structural integrity of bone. Collagen fibrils contain HAP platelets of varying size dispersed between the collagen. We investigate heterotrimeric collagen interaction with HAP using Steering Molecular Dynamics to obtain the force-displacement relation as the collagen is undergoing shearing and peeling on the surface of HAP. Results indicate that the collagen requires 40% less force to separate form the HAP surface under peeling, when compared to shear loading conditions. In both shearing and peeling, the number of …
On The Design And Analysis Of Compliant Mechanisms Using The Pseudo-Rigid-Body Model Concept, 2015 Missouri University of Science and Technology
On The Design And Analysis Of Compliant Mechanisms Using The Pseudo-Rigid-Body Model Concept, Sushrut Gangadhar Bapat
Doctoral Dissertations
"The pseudo-rigid-body model (PRBM) concept, developed for the analysis and design of large-deflection flexible members, has proved over time to be a simple, efficient and accurate tool for the synthesis, analysis and design of compliant mechanisms. This dissertation investigates a variety of compliant mechanism analysis and design problems using the PRBM concept and assists in further advancement of the implementation of the PRBMs. The dissertation begins with the development of a PRBM for a fixed-guided compliant beam with one inflection point in the deformed state. This research investigation advances the concept of characteristic deflection domain to a new synthesis framework …