Mechanical Engineering Commons^™

Application Of The Continuum Damage Mechanics Wilshire-Cano-Stewart (Wcs) Model, Jaime Aaron Cano

Open Access Theses & Dissertations

In this study, the applications of the continuum damage mechanics-based Wilshire-Cano-Stewart (WCS) model are explored to predict rupture time, minimum-creep-strain-rate (MCSR), damage, damage evolution, and creep deformation. Increase knowledge in manufacturing methods has pushed the limit of material science and the development of new materials. Conventional testing is required to qualify materials against creep which according to the ASME B&PV III code, 10,000+ hours of experiments are necessary for each heat before materials are put into service. This process is costly and not feasible for new materials. As an alternative, models have been employed to predict creep behaviors and reduce …

A Central Compact Hybrid-Variable Method With Spectral-Like Resolution, Md Mahmudul Hasan

Open Access Theses & Dissertations

Numerical methods for hyperbolic conservation laws have been a driving force for theresearch in scientific computing and simulation science in the past decades, as many physical, biological, and engineering systems are governed by these equations, such as fluid mechanics, tumor growth, and virtual wind tunnel simulations. Despite the existence of many schemes in the literature, people have never stopped searching for more accurate and efficient methods for these problems. Indeed, the increasing complexity of systems in emerging applications demands better resolution of sub-grid scale phenomenon whereas classical methods usually fail to deliver high-fidelity simulation results of such systems within realistic …

Material Synthesis And Machine Learning For Additive Manufacturing, Jaime Eduardo Regis

Open Access Theses & Dissertations

The goal of this research was to address three key challenges in additive manufacturing (AM), the need for feedstock material, minimal end-use fabrication from lack of functionality in commercially available materials, and the need for qualification and property prediction in printed structures. The near ultraviolet-light assisted green reduction of graphene oxide through L-ascorbic acid was studied with to address the issue of low part strength in additively manufactured parts by providing a functional filler that can strengthen the polymer matrix. The synthesis of self-healing epoxy vitrimers was done to adapt high strength materials with recyclable properties for compatibility with AM …

Suitability Of Low-Cost Additive Manufacturing For Polymer Electrolyte Fuel Cells, David Alexander

Open Access Theses & Dissertations

The purpose of this dissertation is to study the feasibility of low-cost additive manufacturing to fabricate polymer electrolyte fuel cell bipolar plate materials. Traditional manufacturing techniques include molding, milling, hollow embossing, hydro-forming, rolling, and electromagnetic forming. These processes are employed when a design has been selected due to higher costs at low volumes. The combination of high initial costs and bipolar plates being the most expensive component of the polymer electrolyte fuel cell creates incentive to mitigate this obstacle. The feasibility of low-cost additive manufactured bipolar plates will be proven by fabrication, post-processing, and characterization of printed test specimen. The …

All-In-One Multi3d System: Exploring Potential Of 5-Axis Material Extrusion Additive Manufacturing, Angel Vega

Open Access Theses & Dissertations

Additive Manufacturing (AM) has experienced consistent growth since its inception across its seven process categories, especially Material Extrusion (MEX) with systems that can be seen in commercial and industrial settings. As MEX evolves, innovation can be traced in the growing variety of available process materials and new system capabilities leading to greater interest in the technology across various industries including automotive, aerospace and even nuclear weapons. This has created an increasing demand for end-use parts from MEX systems leading to more complex machines with additional Degrees of Freedom (DoF), specialized workflows, and expanded post processing that address the drawbacks of …

Femtosecond Laser Machining Of Drilled Holes In Silicon Nitride, Stephani Nevarez

Open Access Theses & Dissertations

In this study, the laser drilling parameters of a Nd:YAG ultrashort pulsed laser are evaluated to produce zero taper through holes on silicon nitride ceramics. Manufacturing of ceramics is expensive and difficult because of the mechanical and thermal properties of ceramics, limiting applications. Additionally, the high level hardness of the ceramic can affect the ceramic and the manufacturing tool. There is a need to explore non-contact machining such as laser machining to expand the uses of ceramics in industry applications.In order to accomplish this goal, understanding of the physical mechanisms that occurs while laser ablation is needed. Furthermore, the minimum …

Supercritical Co2 Recompression Closed Brayton Cycle Analysis, Andres Eduardo Gutierrez Hernandez

Open Access Theses & Dissertations

On this research, the results of an analysis made of a Supercritical Carbon Dioxide (sCO2) Recuperated Closed Brayton Cycle (RCBC) done by performing theorical calculations and comparing it to the results obtained with the use of the software ASPEN Plus will be presented. To demonstrate and determine that this software is a useful tool for modeling the proposed type of cycle, a preliminary comparison was made to verify with previous studies found in literature. A comparison and analysis between the possible working fluids and thermal energy sources was also performed to emphasize the decision of using CO2 as the cycle …

Synthesis And Characterization Of Tin (Sn) Incorporated Ga2o3, Guillermo Nicolas Gutierrez

Open Access Theses & Dissertations

In this work, we report on the synthesis, characterization of tin (Sn) incorporated gallium oxide Ga2O3 compounds, also included in this work is the effect of tin concentration related to the optical and electrochemical properties. The Sn incorporation into Ga2O3 creates a significant reduction in the bandgap and causes a nonlinear optical activity as the concentration varies. Substantial investigation performed to the structure, phase, and morphology of the mixed compounds governed by the stoichiometry equation Ga2−2xSnxO3-ɗ indicates that the Sn incorporation from 0.00 ≤ x ≤ 0.30 has a significant effect on these properties. To synthesize the Ga-Sn-O compounds a …

Rarified Water Vapor Deposition From Icy Lunar Regolith On An Engineered Cold Plate, Nathaniel Ian Jurado

Open Access Theses & Dissertations

This work presents the fundamental ice collection experiments conducted under rarefied flow regime to develop a high-capacity cryogenic heat pipe for ice recollection on the Moon’s surface. Preliminary ice collection experiments are conducted under cryogenic vacuum environment of 1.5 × 10-2 Torr and -60 °C. The characterization of water vapor sublimation rates from icy lunar regolith (JSC-1A) at various heating powers is established by utilizing a cryogenic thermal vacuum chamber (T-VAC). A custom-built engineered cold plate is designed, manufactured and tested at various degrees of subcooling and vapor sublimation rates. A thin film heater is embedded within the cold plate …

Electron Beam Melted Parameter Development Of Pure Tungsten & Post-Processing Hip And Heat Treatment Of Gamma Titanium Aluminide, Kurtis Isami Watanabe

Open Access Theses & Dissertations

Pure tungsten is a refractory metal and has been gaining interest for the use in nuclear fusion reactors as a plasma facing material. Titanium Aluminide (TiAl) has been growing in popularity as a possibly to phase out Nickel based superalloys due to its high specific strength at elevated temperatures. These two materials suffer from poor machinability due to being brittle at room temperature. Additive manufacturing (AM) is a recently developed manufacturing method that is fundamentally different than formative or subtractive. AM is a layer-by-layer process that has the potential to manufacture metals to a near net shape. Since the AM …

Fabrication Of Alloy 625 Through Electron Beam Powder Bed Fusion Additive Manufacturing, Characterization And Mechanical Performance, Aldo Rubio Hidalgo

Open Access Theses & Dissertations

Electron Beam Powder Bed Fusion (EB-PBF) is an additive manufacturing process that allows for the fabrication of nearly fully dense Alloy 625 parts. In this study EB-PBF Alloy 625 samples were fabricated in an Arcam A2X, heat-treated, then machined and tensile tested. Preliminary process tests varying focus offset, and speed function were conducted to establish baseline process parameter conditions to fabricate Alloy 625 parts based on surface finish and structural defects. The microstructure observed in EB-PBF Alloy 625 parts along the build direction in the as-built state consists of irregularly sized columnar grains averaging 105 μm in width that have …

Phase Transformation And Strain Hardening Mechanisms In Advanced Engineering Steels, Hangyu Dong

Open Access Theses & Dissertations

Strain hardening and associated deformation mechanisms play a determining role in the performance of metallic materials. The objective of the doctoral research was to explore and fundamentally understand the strain hardening mechanisms in the next generation of advanced engineering steels. Two main work hardening mechanisms, notably, twinning-induced plasticity (TWIP) and transformation-induced plasticity (TRIP)) were identified that governed strength and ductility. In the nanograined austenitic steel with high strength-high ductility combination, processed by the novel phase reversion concept, twinning-induced plasticity (TWIP) was the governing deformation mechanism and contributed to good ductility. In striking contrast, transformation-induced plasticity (TRIP) was the deformation mechanism …

Mechanical Properties And Microstructure Evolution Of Thermally Treated Laser Powder Bed Fusion Alsi10mg, Jorge Merino-Gomez

Open Access Theses & Dissertations

The optimization of mechanical properties with thermal postprocessing treatments was investigated in this study across a wide variety of variants. The relationship between heat treatments and the impacts on the mechanical properties and microstructure of printed materials is a crucial part of additive manufacturing. As a result, the current paper provides a comprehensive overview of postprocess heat treatments for Laser Powder Bed Fusion fabricated AlSi10Mg alloy, including stress relief anneals at 190 and 285 degrees Celsius for 2 hours, hot isostatic pressing at 515 degrees Celsius for 3 hours, hot isostatic pressing + T6 treatment for 6 hours, and final …

Development Of A Laser Solder Process For Use With Material Extrusion Additive Manufacturing And Rapid Electronics Prototyping In Embedded Sensing Applications, Emerson Roland Armendariz

Open Access Theses & Dissertations

Industrial and rapid prototyping (RP) trends toward miniaturization of electronic devices containing temperature sensitive electronics and surrounding materials are calling for highly controllable, selective laser soldering technologies. Laser soldering is a non-contact technique that eliminates the risk of marring or damaging sensitive components by precisely focusing a laser beam on a solder filler alloy, leading to a fast and non-destructive electrical joint. Using the benefits of accurate and controlled heat delivery via inexpensive low power laser diodes (LPDL's) in conjunction with ever-increasing additive manufacturing capability in producing complex internal features and geometries, development and testing of a laser application system …

Combustion Of Hydroxylammonium Nitrate Based Monopropellants, Robert Edwin Ferguson

Open Access Theses & Dissertations

"Green" monopropellants based on hydroxylammonium nitrate (HAN) are of interest for replacing highly toxic hydrazine in space propulsion systems and for other applications. Further, gelling such propellants may offer additional advantages such as the long-term stability of compositions with added energetic and catalytic particles in suspension. However, the combustion mechanisms of HAN-based monopropellants and the effect of gelling on their combustion characteristics are poorly understood. In the present work, combustion of an aqueous HAN/methanol solution (70.1 wt% HAN and 14.9 wt% methanol) was studied in a strand burner at nitrogen pressures up to 30 MPa. A version gelled with 1 …

Effect Of Dopants On The Properties And Performance Of Gallium Oxide: Bulk Ceramics And Nanomaterials, Vishal Bhimrao Zade

Open Access Theses & Dissertations

A comprehensive investigation performed in order to understand the fundamental aspects of transition metal (TM) incorporation into Ga2O3, a wide band gap semiconductor with a huge potential for application in electronics, optics, micromechanics and optoelectronics. An approach is presented to tailor the structural, optical, electrical, mechanical properties of Ga2O3 ceramics and thin films. The tungsten (W) mixed Ga2O3 with variable W at% (Ga2-2xWxO3 ; 0.00 ≤ x ≤ 0.30) were synthesized by the high temperature solid state route involving a 2-step calcination process. The solubility limits and phase stability of the compounds are established. While solubility and phase stability occur …

Fabrication And Testing Of Advanced Composites For Extreme Environments, Victoria Centeno

Open Access Theses & Dissertations

The following research focuses on the additive manufacturing and characterization of epoxy syntactic foams that utilize hollow carbon microspheres (CMS) and graphene-coated hollow carbon microspheres (GCMS) as fillers. The matrix that is utilized in this study is a thermoset epoxy resin, chosen for its high strength, low shrinkage, excellent adhesion to various substrates, effective electrical properties, chemical and solvent resistance, low cost, and low toxicity.1 CMS and GCMS were used as fillers for the properties they contribute to the overall epoxy syntactic foam, and can be seen in Fig.1.1. CMS consist of outer stiff carbon and inner gas, giving the …

Multiscale And Multimaterial 3d Printing: Impact Of Feedstock Properties And Processing Parameters On Printed Parts, Kazi Md Masum Billah

Open Access Theses & Dissertations

Material extrusion additive manufacturing (AM) technology is one of the most commonly used technology to fabricate functional prototypes and end-use application parts with custom design. The evolution of the extrusion technology led this particular AM process to grow in many aspects such as new materials development, new design thinking, fabrication of parts in multiscale length, and manufacturing of monolithic parts with multiple functionalities. The research presented in this Dissertation results in the creation of knowledge in material extrusion AM technology with the length scale of production-grade to large-scale 3D printing machine those were used to enable the fabrication of multimaterial …

Microstructural Evolution And Mechanical Properties Of L-Pbf Aerospace Alloys: Hydride- Dehydride Ti-6al-4v And Experimentally Heat-Treated Inconel 718, Jaime Varela

Open Access Theses & Dissertations

Experimental HIP and heat treatment cycles were applied to Laser Powder Bed Fusion fabricated Inconel 718 parts. Recent advances allow for rapid cooling in the HIPing chamber allowing one unit to perform HIP along with other heat treatment cycles such as solution annealing and ageing. Different cycles yield various effects on the porosity reduction as well as the growth of grain in the microstructure, consequently presented different mechanical properties. Specimens were therefore analyzed for density, microstructure, and tensile properties.

In addition, the mechanical and microstructural analysis of HDH Ti-6Al-4V was performed. The high cost of GA Ti64 material is a …

Post Processing Of Electron Beam Melted Ti-6al-4v And Binder Jetted 17-4 Stainless Steel, Ahmad Omar Abu-Issa

Open Access Theses & Dissertations

An extensive assortment of HIP parameters have been altered on EBM fabricated Ti-6Al-4V and have shown that cooling rates of 103 oC/min from temperatures above and below the beta transus produced acicular alpha-prime martensite characteristic elongations < 10 %. Optimum yield strength (0.9 GPa), UTS (1.0 GPa) and elongation (~14 %) were achieved for slow cooling (at 102 oC/min) from 850 oC HIP which produced a dense, Widmanstatten alpha structure within the retained, as-fabricated columnar grains by alpha-prime decomposition. These results suggest that manipulation of AM process parameters to produce a small-grain, equiaxed microstructure, HIPed below the beta transus and slow cooled, will have a wide range of superior, isotropic mechanical properties corresponding to a Widmanstatten alpha microstructure within the equiaxed grains. Also, Binder Jetting printing parameters for differing PSD's of low-cost water-atomized 17-4 Stainless Steel were optimized in order to produce high dense parts. Densities ranging from 94-97.5% were achieved, and issues of inhomogeneous porosity were addressed using a fumed silica flow additive.

Synthesis And Characterization Of Functiona Materials For 3d Printed Composites, Elizabeth Irene Reza

Open Access Theses & Dissertations

The following body of work encompasses the synThesis, upscaling, additive manufacturing, and characterization of microspheres as functional fillers incorporated into polymer syntactic foams. Synthesizing microspheres permits control over morphology, dispersion of particles, and size while the use of direct write manufacturing allowed for the controllability of filler orientation. Two different syntactic foams were developed from similar methodologies: (1) a silicone syntactic foam (2) epoxy syntactic foam. The silicone epoxy foam showed an increasing in damping and elastic modulus. The epoxy syntactic foams showed an enhanced thermal and electrical properties.

Real-Time Intelligent And Multi-Spectral Inspection Of Structural Components, Mst Mousumi Rizia

Open Access Theses & Dissertations

Conventional, manual inspection methods are the most commonly used inspection approaches to this day; that cause downtime and can be erroneous due to their repetitive nature, heavy workload, and human error. The overarching goal of this work is to advance structural inspection with intelligent and autonomous techniques across infrastructures. In particular, this project will develop path-planning schemes for close navigation around the structures and intelligent algorithms for crack and corrosion detection.

The introduced novel navigation method uses advanced manufacturing techniques to generate aerial inspection trajectories in GPS-denied areas. The proposed method is validated using the `Gazebo' robotics simulator; the results …

A Probabilistic Creep Constitutive Model For Creep Deformation, Damage, And Rupture, Md Abir Hossain

Open Access Theses & Dissertations

The structural analysis of Industrial Gas Turbine (IGT), Aeroengine, Gen IV nuclear components under in-service conditions at various stress and temperature are susceptible to time-dependent creep deformation and creep induced failure. Such failure phenomena are exacerbated by the randomness in material properties, oscillating loading conditions, and other sources of uncertainty. The demand for physically based probabilistic creep modeling is highly sought by alloy designers. The objective of this study is to develop and validate a probabilistic creep-damage model incorporating multi-sources of uncertainty to replace the traditional deterministic and empirical decision-based modeling. In this study, the deterministic Sine-hyperbolic (Sinh) creep-damage model …

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 …

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 …

Brian Valdez - Dynamics And Control Of A 3-Dof Manipulator With Deep Learning Feedback, Brian Orlando Valdez

Open Access Theses & Dissertations

With the ever-increasing demands in the space domain and accessibility to low-cost small satellite platforms for educational and scientific projects, efforts are being made in various technology capacities including robotics and artificial intelligence in microgravity. The MIRO Center for Space Exploration and Technology Research (cSETR) prepares the development of their second nanosatellite to launch to space and it is with that opportunity that a 3-DOF robotic arm is in development to be one of the payloads in the nanosatellite. Analyses, hardware implementation, and testing demonstrate a potential positive outcome from including the payload in the nanosatellite and a deep learning …

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, …

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 …

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 …