Mechanical Engineering Commons^™

Large-Scale Inflatable Structures For Tunnel Protection: A Review Of The Resilient Tunnel Plug Project, Eduardo M. Sosa, Gregory J. Thompson, Gregory M. Holter, John M. Fortune

Faculty & Staff Scholarship

The protection of underground civil infrastructure continues to be a high priority for transportation and transit security agencies. In particular, rail transit tunnels running under bodies of water are susceptible to disruptions due to flooding caused by extraordinary climatic events such as hurricanes or other events resulting from human activities. Several events have taken place in the past decades that have demonstrated the need to mitigate vulnerabilities or, at least, minimize the consequences of catastrophic events. Although it is impossible to prevent all situations that can lead to flooding, damage can be substantially decreased by reducing the area affected by …

Editorial For The Special Issue On Micro/Nano-Chip Electrokinetics, Volume Iii, Shizhi Qian, Xiangchun Xuan

Mechanical & Aerospace Engineering Faculty Publications

No abstract provided.

A Review Of Problem Structuring Methods For Consideration In Prognostics And Smart Manufacturing, Patrick T. Hester, Andrew J. Collins, Barry Ezell, John Horst

Engineering Management & Systems Engineering Faculty Publications

Successful use of prognostics involves the prediction of future system behaviors in an effort to maintain system availability and reduce the cost of maintenance and repairs. Recent work by the National Institute of Standards and Technology indicates that the field of prognostics and health management is vital for remaining competitive in today’s manufacturing environment. While prognostics-based maintenance involves many traditional operations research-centric challenges for successful deployment such as limited availability of information and concerns regarding computational efficiency, the authors argue in this paper that the field of prognostics and health management, still in its embryonic development stage, could benefit greatly …

Effect Of O2 Concentration In Ambient Mixture And Multiphase Radiation On Pollutant Formation In Ecn Spray-A, Khaled Mosharraf Mosharraf Mukut, Somesh Roy

Mechanical Engineering Faculty Research and Publications

The present study investigates the formation and evolution of soot and NO_X in a high-pressure constant-volume combustion chamber. This work focuses on the effect of multiphase thermal radiation and O₂ dilution in ambient/exhaust gases, some- times also referred to as exhaust gas recirculation(EGR), qualitatively and quantitatively. The spray-A case (n-dodecane as fuel) from Engine Combustion Network (ECN) is used as the target condition. Two different soot modeling approaches have been considered: a semi-empirical two-equation model and a detailed method of moments with interpolative closure (MOMIC) model. A multiphase photon Monte Carlo (PMC) solver with line-by-line (LBL) spectral data …

Structure-Property-Performance Evaluation Of Refractory Metal Incorporated Gallium Oxide Thin Films For Extreme Environment Applications, Anil Krishna Battu

Open Access Theses & Dissertations

An approach is presented to design refractory-metal (RM) incorporated Ga2O3-based materials with controlled structural, mechanical, and optical properties. A model system based on molybdenum (Mo) doped Ga2O3 (GMO) has been considered to elucidate the combined effect of RM-doping and processing parameters on the properties and oxygen sensor performance of GWO nanomaterials. The molybdenum (Mo) content in Ga2O3 was varied from 0 to 11 at% in the sputter-deposited Ga-Mo-O films. Molybdenum was found to significantly affect the structure and optical properties. While low Mo content (≤4 at%) results in the formation of single-phase (β-Ga2O3), higher Mo content results in amorphization. Chemically …

Low Weight Design Of A Pressure-Fed System For A Small Payload Launch Vehicle, Lucero Buendia

Open Access Theses & Dissertations

Carbon fiber reinforced polymer (CFRP) composites have become of great interests to aerospace industries because of their low-cost, lightweight and their tailorable mechanical properties. In aerospace structures, for example, heavy metals have been used in cryogenic fuel and oxidizer tanks for over 50 years. However, weight savings can be substantial if materials such as composites are used instead. From Delta IV heavy-lift launch vehicle it is known that cryogenic composite tanks can save approximately up to 30% of weight in fuel and oxidizer tanks. Although there is a wealth of studies in the mechanical behavior of composites at room temperature, …

The Effect Of K2co3 Concentration In Kerosene Emulsions On Spray Droplet Sizes For A Magnetohydrodynamic Power Generator, Alejandra Castellano

Open Access Theses & Dissertations

Potassium carbonate (K2CO3) is an effective seeding material to introduce potassium vapor in oxy-fuel combustion to create a conductive plasma. Injecting potassium carbonate before combustion promotes particle volatilization and improves the generation of potassium vapor. This can be achieved by emulsifying a potassium carbonate solution with kerosene. Several studies have investigated creating stable emulsions with kerosene with water by using differing surfactants. However, the effects of using varying concentrations of K2CO3 dissolved in deionized water have not been fully explored. Based on methods of creating successful emulsions, the development of a successful mixture comprised of kerosene and K2CO3 solution is …

Laser Diagnostics Of Compressible And High-Intensity Premixed Methane-Air Combustion Inside A Backward Facing Step Combustor Using High- Repetition Rate Ch-Plif And Piv, Md. Amzad Hossain

Open Access Theses & Dissertations

A novel high repetition rate (10 kHz) planar laser-induced fluorescence (PLIF) diagnostic technique was used for the flame front study. Premixed methane-air combustion was studied at different flow turbulence conditions (Re = 15000, 30000 and 64000; 12CFM, 25CFM and 50 CFM; 10m/s, 20 m/s and 40 m/s) and fuel loading (Փ =0.6 to 1.2). The study used an optically accessible backward-facing step high-speed combustor. Methane-air mixture was supplied to the combustor at atmospheric pressure and standard room temperature (T =25°C). CX-CH PLIF was used to detect the actual flame front structures. The flame dynamics were then correlated to the flow …

An Accelerated Creep Testing Program For Nickel Based Superalloys, Robert M. Mach

Open Access Theses & Dissertations

In order to improve the energy production within the United States, new materials are developed with the goal of increased functionality. These materials are required to perform at extreme pressures and temperatures (up to and beyond 200MPa and 650â??) as well as be sustainable beyond 105 hours. Before developing these materials into components for power generation, mechanical testing is required to better understand the behavior of these materials at various loads and temperatures. The longest of these tests is the conventional creep test which is a real time test that can beyond 105 hours depending on service conditions. Hundreds of …

Velocity Measurements Using A Piezoelectric Plate As A Sensor, Paul Perez

Open Access Theses & Dissertations

In this study, the voltage output from a piezoelectric sensor placed in a test section is used to predict flow velocity changes. The piezoelectric made of PZT is thought to be advantageous due to its fast response time, potential durability at higher temperatures, and self-powered characteristics. Having said that this sensor could be implemented into the Hybrid Performance Project built by NETL to characterize and mitigate the probability of compressor surge and stall. The problem arises because of the added large volume between compressor and gas turbine and resultant changes to system fluid dynamics. The effect of the piezoelectric sensor …

Computational Methods For Creep Modeling, Ricardo Vega

Open Access Theses & Dissertations

Creep is an important phenomenon present in the power generation and aerospace industry. Creep is a mechanism that degrades the quality of a part, such as the turbines used in different industries, when elevated temperatures and loads are applied. Creep damage can cause critical failures that can cost millions of dollars and as such, prevention is important. A multitude of creep models exist to help with design and failure prevention. These models are applied using computational tools which allows the engineer to properly predict the life of a part or other material properties. In this work various creep numerical optimization …

High Pressure High Heat Flux Pool Boiling Test Facility Design To Investigate Nucleation Boiling Heat Transfer Enhancement Using Micro/Nano-Scale Engineered Structures, Omar Hernandez Hernandez Rodriguez

Open Access Theses & Dissertations

Developing efficient heat dissipation technologies is of critical importance towards the development and the commercialization of next-generation compact and high-performance electronic devices, cooling systems, power generation systems and chemical processing units, as well as retrofitting the existing thermal management schemes. As such, phase change heat transfer systems, more specifically boiling heat transfer systems, have attracted significant attention due to their ability to extract a large amount of latent energy stored within the fluid. Pool boiling is an efficient mode of phase change heat transfer processes accompanied by nucleation of vapor bubbles from liquid on to the hot surfaces, bubble growth, …

Development Of A Multi-Axis Wire Embedding Device For A Large Area Thermoplastic Pellet-Fed Additive Manufacturing System, Christopher Jasiel Minjares

Open Access Theses & Dissertations

This research focused on the development and implementations of a six degrees of freedom (6DOF) articulated arm onto a Big Area Additive Manufacturing (BAAM) system to interact with complex 3D geometries. BAAM is a large-scale machine which falls under material extrusion additive manufacturing (AM) - a process that selectively dispenses molten plastic layer-by-layer. The development of the 6DOF articulated arm required a mechanical design which went through several iterations before getting to the final design. Also, implementation of the tool was performed with the help from Cincinnati Incorporated (CI) which is the company that developed the BAAM.

First, the mechanical …

A High-Temperature Valve Design For A Solid Oxide Fuel Cell/Gas Turbine Hybrid System, Cynthia Morales

Open Access Theses & Dissertations

Systems containing high heat generation require thermal management, especially in a solid oxide fuel cell gas turbine (SOFC/GT) hybrid system. The startup of each system in a standalone configuration may be a trivial approach, but when coupled together, different dynamics are experienced. The SOFC/GT provide high theoretical efficiency due to the ability to recover the extra heat produced by the fuel cell (FC) to drive the gas turbine (GT). After recovering the energy recuperated in the GT, the exhaust gas heats the cathode inlet flow to the FC which is an advantage during nominal operation of the cycle but not …

Oxidation Of Niobium Silicides Obtained By Self-Propagating High-Temperature Synthesis, Frank Anthony Perez

Open Access Theses & Dissertations

Niobium silicide-based composites are promising materials for high-temperature structural applications, such as gas turbines. One attractive method for their fabrication is mechanically activated self-propagating high-temperature synThesis (MASHS). However, oxidation resistance of niobium silicides produced by MASHS has not been studied yet. In this present work, the oxidation of Nb/Nb5Si3 composites obtained by MASHS was investigated by using non-isothermal thermogravimetric analysis (TGA) and differential scanning analysis (DSC). Both techniques have shown that the oxidation starts at about 500 °C and the materials become fully oxidized at 750 â?? 800 °C. Model-based analysis of the TGA data has shown that the Avrami-Erofeev …

Multi-Wavelength Pyrometry For Emissivity Mapping And Accurate Surface Temperature Measurement In Powder Bed Fusion Systems, Md Moinuddin Shuvo

Open Access Theses & Dissertations

Accurate surface temperature measurement within powder bed fusion (PBF) systems during fabrication remains elusive for many reasons, despite the importance of knowing temperature for improving part quality, process control, repeatability and reproducibility, simulation capabilities, and more. Multi-wavelength (MW) pyrometry has been used previously to measure off-axis temperatures of a small region (~2.6mm in diameter) within an electron beam PBF (EBPBF) system. While this small region measurement makes it difficult to get a full field temperature map of the powder bed, it also allows for inline (on-axis) with laser temperature measurements for laser PBF (LPBF) systems. The MW pyrometry technique determines …

Mechanically Activated Combustion Synthesis Of Niobium Silicide Based Composites, Reina Trevino

Open Access Theses & Dissertations

Niobium silicide-based composites are promising materials for high-temperature structural applications, such as gas turbines, but their implementation is hindered by the lack of effective processing methods. Self-propagating high-temperature synThesis (SHS) is an attractive method for fabrication of advanced materials. However, it is difficult to perform SHS of niobium silicides because the melting point of Nb is higher than the combustion temperature, which greatly inhibits Nb-Si reaction. To ignite an Nb/Si mixture and obtain Nb5Si3, the desired phase in niobium silicides, either preheating or mechanical activation of the mixture is necessary. This problem becomes even more critical in the SHS of …

Qualification And Implementation Of A Liquid Oxygen/ Liquid Methane Data Acquisition System, Zachary Welsh Welsh

Open Access Theses & Dissertations

One of the primary goals of the MIRO Center for Space Exploration and Technology Research (cSETR) is the design and testing of liquid oxygen and liquid methane rocket engines. As of this thesis’ time of writing, two engines are currently undergoing testing at the center’s Technology Research and Innovation Acceleration Park (tRIAC), located in Fabens, Texas. The engines vary in scale starting with a 5 lbf Reaction Control Engine (RCE) to a 500 lbf engine dubbed the Centennial Restartable Oxygen Methane Engine (CROME). It was necessary to develop a control and data acquisition system to support these various test campaigns, …

Effect Of Flow Velocity And Geometry On The Signal From A Piezoelectric Flow Rate Sensor, Jad Gerges Aboud

Open Access Theses & Dissertations

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Accurate Replication Of An Ear Pinnae Geometry For Use In Acoustic Testing Of Spatial Cues And Sound Localization, Alejandra Belmont

Open Access Theses & Dissertations

Additive manufacturing (AM) enables freedom of design as well as fabrication of complex objects such as the human hear. In medical modeling there is a need for patient-specific customizable parts. The outer human ear consists of these main parts: the pinna, which naturally filters sound, and the ear canal, which is the point at which sound enters before being moved up to the tympanic membrane, otherwise known as the eardrum. In an attempt to accurately replicate ear models, the use of scanning and reverse engineering methods was used. A comparison of 3D laser scanning systems was performed to determine their …

The Dynamic Transition Of A Vertical Take-Off And Landing Drone, Luis Carlos Calvo Jr.

Open Access Theses & Dissertations

Unmanned aerial vehicles, or UAVs, are small pilotless aircrafts that are remotely controlled through a ground control station. They have increased in popularity because of their applications and the advantages that each UAV can provide based on their need. There are many types of UAVs, but this study focuses on a type of Vertical Take-Off and Landing (VTOL) UAV that is known as the Albatross UAV. This UAV was manufactured by a company known as Applied Aeronautics, and configurations were made to change the fixed-wing (FW) UAV to a VTOL UAV. This study was done to find methodologies to simulate …

Design And Additive Manufacturing Of Shape Recovery Polymer Lattice Structure, Chien-Chun Chou

Open Access Theses & Dissertations

Studied mechanical properties of 3D printed metamaterials of BCC, FCC, and BFCC structure.

Uav Parameter Estimation Through Machine Learning, Andres Enriquez Fernandez

Open Access Theses & Dissertations

Parameter identification of Unmanned Aerial Vehicles (UAV) is very helpful for understanding cause-effect relationships of physical phenomenon, investigating system performance and characteristics, fault diagnostics, control development/tuning, and more. Traditional ways of performing parameter identification involve establishing a mathematical model that describes the system's behavior. The equations in the model contain parameters that are estimated indirectly from measured flight data. This parameter identification process requires knowledge of the physics involved. Also, it necessitates a careful consideration of the aircraft instrumentation for accurate measurements. It also requires careful design of the flight maneuvers to ensure thorough excitation of the flight dynamics involved. …

Development Of Recepticals And Joints For Embedded Electronic Components Inserted During Print Via Hybrid Thermoplastic-Based Additive Manufacturing, Leonardo Isaac Gutierrez Sierra

Open Access Theses & Dissertations

The use of hybrid additive manufacturing (AM) systems is a novel approach in the fabrication of multi-functional parts. 3D printed electronics are an example of multi-functional parts fabricated using the Foundry Multi3D System, a hybrid AM system. Previous research has demonstrated the capabilities of the system by manufacturing RF antennas and satellite panels with embedded electronics, to name a few. However, research to identify design clearances and establish a manufacturing process plan had not been performed. The purpose of this manuscript is to determine the correct clearances for foreign components to be inserted unto a partially printed substrate. Besides this …

Mechanical Performance Of Ebm Ti-6al-2sn-4zr-2mo Influenced By The Effects Of Different Hot Isostatic Pressing Treatments, Miguel Lopez

Open Access Theses & Dissertations

Electron Beam Melting (EBM) is an additive manufacturing process that presents a lower level of internal defects in comparison to Selective Laser Melting (SLM). Pairing Hot Isostatic Pressing (HIP) with Additive Manufactured metal parts, sub-surface voids can be eliminated through high pressure and temperature. This significantly improves fatigue life, impact toughness, creep, rupture strength, and tensile ductility. In this investigation, Ti-6Al-2Sn-4Zr-2Mo samples manufactured in the Arcam's Q20 system will be tested as per ASTM E8 Standard Test Methods for Tension Testing of Metallic Materials. Different variants of Hot Isostatic Pressing (HIP) treatments were analyzed and compared. Tensile testing was performed …

Development Of An Automated Ultrasonic Wire Embedding Process For Use With Material Extrusion Additive Manufacturing And Rapid Electronics Fabrication, Nikki L. Martinez

Open Access Theses & Dissertations

Polymers have been used in Additive Manufacturing (AM) by many industries for rapid prototyping. Parts created using polymer AM however are known to be relatively expensive thus limiting them to small volume production and making them inapplicable for mass production, while their inherent porous and anisotropic properties make them mechanically inferior to parts made using traditional methods such as injection molding. As projects demand more efficient designs, and at the same time ask for more complex features, AM, combined with other manufacturing processes, like Ultrasonic Wire embedding, can streamline and consolidate assemblies. In the realm of composite and multifunctional assemblies, …

Design Of Experiments Analysis Of Powder Removal Methods For Ebm Manufactured Ti-6al-4v Parts, Luis Cesar Ramos Castañeda

Open Access Theses & Dissertations

Additive Manufacturing is a technology that allows the on-demand manufacturing of complex geometries that cannot be fabricated through traditional subtractive manufacturing methods. Powder Bed Fusion is one of the seven categories of Additive Manufacturing with two subcategories, the Laser Beam Melting and the Electron Beam Melting. Freedom of design, rapid prototyping, and customization are some of the benefits that this technology provides. Like any technology, there are limitations for each category and subcategory. The Electron Beam Melting uses the electron beam to pre-heat the powder bed, reducing the temperature difference between the build part and powder bed, causing the surrounding …

Direct Numerical Simulations Of Acoustic Disturbances In Various Rectangular Nozzle Configurations, Nathaniel Hildebrand, Meelan M. Choudhari, Lian Duan

Mechanical and Aerospace Engineering Faculty Research & Creative Works

We perform Direct Numerical Simulations (DNS) to study the acoustic freestream disturbances radiating from the turbulent boundary layers along the contoured nozzle walls of a hypersonic wind tunnel with a rectangular test section. To begin with, the effects of the spanwise end walls are suppressed by confining the spanwise computational domain to a finite segment of the overall nozzle cross section and by imposing periodic boundary conditions across that spanwise domain. Besides providing a building-block configuration to reveal partial effects of the enclosed acoustic environment within the wind tunnel, these computations serve as a steppingstone toward the goal of fully-3D …

Direct Numerical Simulation Of Turbulent Pressure Fluctuations Over A Cone At Mach 8, Junji Huang, Lian Duan, Katya M. Casper, Ross M. Wagnild, Neal P. Bitter

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Direct numerical simulations (DNS) were conducted to characterize the pressure fluctuations under the turbulent portion of the boundary layer over a sharp 7◦ half-angle cone at a nominal freestream Mach number of 8 and a unit Reynolds number of Reunit = 13.4 x 106/m. The axisymmetric cone geometry and the flow conditions of the DNS matched those measured in the Sandia Hypersonic Wind Tunnel at Mach 8 (Sandia HWT-8). The DNS-predicted wall pressure statistics, including the root-mean-square (r.m.s.) fluctuations and the power spectral density (PSD), were compared with those measured in the Sandia HWT-8. A good comparison between the DNS …

Real-Time Assembly Operation Recognition With Fog Computing And Transfer Learning For Human-Centered Intelligent Manufacturing, Wenjin Tao, Md Al-Amin, Haodong Chen, Ming-Chuan Leu, Zhaozheng Yin, Ruwen Qin

Mechanical and Aerospace Engineering Faculty Research & Creative Works

In a human-centered intelligent manufacturing system, every element is to assist the operator in achieving the optimal operational performance. The primary task of developing such a human-centered system is to accurately understand human behavior. In this paper, we propose a fog computing framework for assembly operation recognition, which brings computing power close to the data source in order to achieve real-time recognition. For data collection, the operator's activity is captured using visual cameras from different perspectives. For operation recognition, instead of directly building and training a deep learning model from scratch, which needs a huge amount of data, transfer learning …