Digital Commons Network^™

Incorporating In-Situ Monitoring To Detect Anomalies In Additively Manufactured Kovar Steel On A Layer-To-Layer Basis, Matthew Aragon

Mechanical Engineering ETDs

Combining traditional methods of material analysis with in-situ monitoring of a Laser Powder Bed Fusion (LPBF) printed part, on a layer-to-layer basis, provides the data necessary to adjust printing parameters to achieve specific material properties. Additively manufactured technology has advanced in the ability to accommodate new materials and provide new use cases. Uncertainties in material properties have arisen alongside the advancements in additive manufacturing. The layer-wise print analysis will allow for detection and correlation of print anomalies to the material properties such as density, material strength, and surface roughness. The data processed from each layer will be used to further …

Three-Dimensional Lattices As Effective Impact Absorption Layers For Space Applications, James Youchison

Mechanical Engineering ETDs

Additive manufacturing (AM) is increasingly becoming a viable manufacturing process due to dramatic advantages that it facilitates in the material selection and design complexity. This paper investigates the potential of additively manufactured lattice structures for the application of dissipating impact energy. In this research the role of geometry and material properties on the static and dynamic energy absorption properties of additively manufactured wave spring lattices composed of various materials were studied under drop/impact and compression tests. A finite element simulation of the lattice structure was also conducted, although the results were overall inconclusive, it gave some great insight into the …

Interaction Of A Shock Wave With A Particle Curtain, Daniel M. Freelong

Mechanical Engineering ETDs

This thesis presents an experimental study of the interaction of a normal shock wave with a sparse curtain of particles. Soda lime particles with a nominal diameter of 40 micrometers are used to form the curtain. A high speed camera captured several segments of the particle curtain flow from the front view, including the early formation stages. The frames from the video segments were then extracted into individual sequential images. Properties were found using the images such as the velocity fields, time evolution of multiphase Atwood number, and perturbation growth. Volume fractions were derived from mass discharge measurements and particle …

Dynamic Hvac Energy Management Using Commercial Building Occupancy Metrics & Neural Networks, Krishna Chaitanya Jagadeesh Simma

Civil Engineering ETDs

With the rise of technology use in buildings, it is now possible to collect data that can be used to improve building energy consumption. One factor that has significant impact on building energy consumption is occupancy. Recent studies have shown promising results in obtaining occupancy information from existing infrastructure such as WiFi router networks. However, these existing frameworks require additional investments through software upgrades, added infrastructure, computational resources, and may raise occupant privacy concerns. Additionally, with occupant thermal comfort statistics being lower than ASHAREA specified standards, a novel approach for indoor climate control is needed. To address the limitations in …

Airborne Counter-Uncrewed Systems With Runtime Assurance Control, Isaac J. Seslar

Mechanical Engineering ETDs

This thesis develops a response to the increase in the availability of the commercially available uncrewed aerial systems and is dedicated to the detection, classification, and tracking required to successfully neutralize when determined malicious. A requirement of actively avoiding obstacles using runtime assurance is addressed and designed to keep the hardware safe in potentially dangerous situations. This work will elaborate on the several components the test bed is comprised of, specifically the hardware and software portions that successfully solve the problem. The software encompasses the simulation, the multiple algorithms required for the tracking, and the machine learning required for detection …

A Practical Methodology To Detect, Quantify And Characterize Experimental Uncertainties In The Dynamic Testing Of Structures, James L. Woodall

Civil Engineering ETDs

This thesis investigates the uncertainty in the experimental context of structural dynamics. This thesis proposes a method to estimate both the effect of boundary conditions, as well as two different methods to detect the location of sensors on a specimen. Firstly, this thesis proposes a technique to predict the dynamic behavior of any point along a cantilever beam with an uncertain transverse elastic restraint. Secondly, this thesis investigates the estimation of the location of a sensor given the output data of a physical experiment with two different methods. Small errors in the sensor location may go unnoticed in the frequency …

Printing Parameter Determination And Characterization Of Additively Manufactured Kovar Steel, Will Macgreggor Davidson

Mechanical Engineering ETDs

Kovar (ASTM F15, UNS K94610) steel has many applications across Sandia National Laboratories but is best known within academia and industry for its glass-to-metal and glass-to-ceramic hermetic sealing capabilities. Successful printing parameters for a Renishaw AM400 to additively manufacture artifacts from Kovar steel powder have been determined. The printed test artifacts have been studied for ultimate tensile strength, density, surface roughness, hardness, bulk composition, and impact toughness. Longer throughput measurements such as porosity, coefficient of thermal expansion, and grain structure studies have been established for future delivery to the research team. Yet another delivery from this thesis research is a …

Feasibility Study Of A Structural Electrolyte Containment Ring For Use In Thermal Batteries, Teal Harbour

Mechanical Engineering ETDs

The feasibility of a new thermal battery separator design utilizing a structural machined MACOR® ceramic is explored. The cylindrical ceramic “separator ring” maintains separation of cell electrodes while containing a LiCl-KCl molten salt electrolyte. Finite element analysis (FEA) results show the separator ring can withstand mechanical and thermal loading conditions representative of a thermal battery environment. Electrical Impedance Spectroscopy (EIS) was used to characterize impedance mechanisms. EIS data was also used to calculate and show conductivities of the experimental separators are comparable to a traditional pellet. Although discharge testing resulted in high current-pulse resistivities and low delivered capacity, the work …

Fundamental Dislocation Solutions For Infinite And Semi-Infinite Media, Luo Li Mr

Mechanical Engineering ETDs

Much research has gone into determining stress fields of dislocation, as the understanding of dislocations is fundamental to understanding metal or crystal plasticity. In this thesis, the stress field of a rectangular dislocation loop in an infinite isotropic solid is developed for a Volterra-type dislocation with three non-zero Burgers vector components. Also, the stress and strain fields of a rectangular dislocation loop in an isotropic solid, which is a semi-infinite medium, are obtained here for a Volterra-type dislocation. Moreover, analytical and numerical verifications of the developed stress/strain fields are performed. This is done by ensuring the satisfaction of the equilibrium …

Performance Improvements For Next Generation Falling Particle Receiver Systems, Nathan R. Schroeder

Mechanical Engineering ETDs

Falling particle receiver (FPR) systems are a rapidly developing technology for concentrating solar power applications. Solid particles are used as both the heat transfer fluid and thermal energy storage media. Through the direct solar irradiation of the solid particles, flux and temperature limitations of tube-bundle receives can be overcome leading to higher operating temperatures and energy conversion efficiencies. Particle residence time, curtain opacity, and curtain stability affect the performance of FPR designs. As the particles fall through the receiver the curtain accelerates, increasing its transmissivity thus decreasing the amount of energy absorbed. Multistage release trough structures catch and release the …

Prefilling Mylar Capacitor Edge Margins To Improve Capacitor Reliability And Size, Chase Kayser

Mechanical Engineering ETDs

Typical high-voltage, wound film-foil capacitors have large edge margins filled with air to prevent breakdown between foil electrodes. This arrangement is inefficient for energy density and leaves a volume where particulates may settle in an uncontrolled atmosphere. The reliability and size of high-voltage, wound film-foil capacitors could be improved by adding a material with higher breakdown strength into the edge margins. This will not only improve reliability and size but also act as a barrier to prevent foreign object debris (FOD), volatile organic compounds (VOCs), and water from damaging the capacitor’s performance. This paper will discuss the process of determining …

Polarity Effects Of Aluminium Nitride Thin Films And Morphological Characterization Of Molybdenum Thin Films, Aseem Poudyal

Mechanical Engineering ETDs

AlN (Aluminium Nitride) is a piezoelectric material that is often used in numerous applications as a transducer. C-axis crystal orientation control of AlN is very important as it corresponds to a high piezoelectric coefficient. Crystal orientation of sputtered AlN is strongly affected by its deposition parameters such as sputtering pressure, target to substrate distance, growth temperature, gas pressure and frequency/duty cycle in the case of pulsed DC sputtering. Crystal orientation of AlN depends on the energy of the sputtered atom and the mobility of the adatoms on the surface of the substrate. Varying the deposition parameters can alter the kinetic …

The Development Of All Solid-State Optical Cryo-Cooler, Junwei Meng

Optical Science and Engineering ETDs

This dissertation describes the development of an all solid-state optical cryo-cooler. Crystals of 10% wt. ytterbium-doped yttrium lithium fluoride (Yb³⁺:YLF) are used to cool an infrared HgCdTe sensor payload to an absolute temperature below 135 K, equivalent to delta T equal 138 K below ambient. This record level of cooling is accomplished with a single stage, in a completely vibration-free environment, with a corresponding cooling power of 190 mW. This milestone is made possible by the design and fabrication of an undoped YLF thermal link that efficiently shields the payload with a non-right angle kink from intense anti-Stokes …

Target Control Of Networked Systems, Isaac S. Klickstein

Mechanical Engineering ETDs

The control of complex networks is an emerging field yet it has already garnered interest from across the scientific disciplines, from robotics to sociology. It has quickly been noticed that many of the classical techniques from controls engineering, while applicable, are not as illuminating as they were for single systems of relatively small dimension. Instead, properties borrowed from graph theory provide equivalent but more practical conditions to guarantee controllability, reachability, observability, and other typical properties of interest to the controls engineer when dealing with large networked systems. This manuscript covers three topics investigated in detail by the author: (i) the …

Emissivity Measurements Of Painted And Aerosol Deposited Thermographic Phosphors (Yag:Dy And Mfg:Mn), Wendy Flores-Brito

Mechanical Engineering ETDs

Combustion is one of the most difficult processes to model. Luminous flames are characteristically sooty, which creates a problem when modeling and calculating the combustion and heat transfer of the process; both of which are highly dependent on temperature and emissivity. Soot particle emissivity as well as gas contributions affect the heat transfer calculation and must be accounted for.

Thermographic phosphors (TP) are ceramic based phosphorescent materials that have a temperature dependent emission that can be exploited to obtain surface and gas temperature measurements, as well as 2D temperature maps. Emissivity knowledge is not needed to obtain temperature and is …

Qualitative Investigation Of Gaseous Hydrodynamic Mixing Model Efficacy And Associated Sensitivity, Caleb White

Mechanical Engineering ETDs

A mixing model analyzes the mixing of helium (He) and sulfur hexafluoride (SF₆) according to two classical gaseous equations of state (EOS), namely, Amagat’s Law and Dalton’s Law, undergoing planar traveling shocks in three dimensions (3D). Numerical simulations utilize the Sandia National Laboratories (SNL) shock hydrodynamic code CTH and other codes including the SNL thermochemical equilibrium code TIGER and the uncertainty qualification (UQ) and sensitivity analysis code DAKOTA. Comparison with experimental results show that none of the equations of state are able to accurately predict the properties of the shocked mixture; similar discrepancies have been observed in previous …

The Effect Of Including Pressure Within Cracks On Failure Times Of Cylinders Subjected To Internal Air Blast Loading, Molly M. Bailey

Mechanical Engineering ETDs

The importance of internal crack pressure on the extent of crack propagation is studied using both numerical and experimental results. Experimental data were obtained from shock tube testing of internally pressurized quasi-brittle hollow cylinders loaded to failure. Half of the samples were tested with an inserted membrane that transferred the shocked fluid load but prevented the fluid from entering the developing cracks. In the other cases, the membrane was removed allowing the fluid to enter the crack and assist development of fracture. A novel approach to modeling this complex structural response involving dynamic failure and fluid structure interaction is presented, …

Additively Manufactured Continuous Carbon Fiber Thermoplastic Composites For High-Performance Applications, Nekoda Van De Werken

Mechanical Engineering ETDs

The goal of this dissertation is to provide a foundation for the advancement of additive manufacturing (AM) toward production of high-performance carbon fiber reinforced polymer matrix composites (CFRPs). AM can provide valuable advantages over conventional composite manufacturing techniques, including the control over fiber orientation, capability of manufacturing complex geometries, out-of-autoclave processing, elimination of the need for composite tooling, and the ability to perform lights-out manufacturing. Currently, however, a suite of challenges related to modelling, design, manufacturing defects, and general limitations in the current understanding of the processing-structure-property relationships exist in AM of composites. To this end, this dissertation investigates novel …

Development Of Mbd Model And Analysis Methodology For Vehicle Design, Alfonso Christopher Ponce

Mechanical Engineering ETDs

This thesis is to provide a new methodology that considers the effects the chassis applies during dynamic load to the suspension and the handling characteristics of a road course vehicle. A methodology in which is described in detail as well as an applied demonstration where literature before this thesis, lacks in replication and serves to establish a basis for multi-body dynamic analysis in this area. Two models to be created, rigid and flexible, and to compare each other to study the effects the chassis torsional stiffness has during load transfer. Ultimately, to assist in the design of a vehicle that …

Mechanical Characterization Of Additively Manufactured Inconel 625 And Alsi10mg Via High-Throughput Tensile Testing, Aron Robbins

Mechanical Engineering ETDs

Additive manufacturing allows for the development of complex geometrical designs that may otherwise be impossible to fabricate through common methods. This advantage has opened the door to a new testing method capable of rapid and efficient material property characterization and qualification. The technique exhibits how 100’s of sub-size tensile bars can be tested to show an inherent statistical variation of materials produced by laser powder bed fusion. The testing technique presented is used to evaluate various heat treatments of the nickel super-alloy Inconel 625 and the aluminum alloy AlSi10Mg after stress relief annealing. Statistical analysis using 3-parameter Weibull distributions is …

Optimal Control Strategies For Complex Biological Systems, Afroza Shirin

Mechanical Engineering ETDs

To better understand and to improve therapies for complex diseases such as cancer or diabetes, it is not sufficient to identify and characterize the interactions between molecules and pathways in complex biological systems, such as cells, tissues, and the human body. It also is necessary to characterize the response of a biological system to externally supplied agents (e.g., drugs, insulin), including a proper scheduling of these drugs, and drug combinations in multi drugs therapies. This obviously becomes important in applications which involve control of physiological processes, such as controlling the number of autophagosome vesicles in a cell, or regulating the …

Post-Polymerization Modification Of Kapton Using Electron Beam Irradiation, Luis A. Hernandez

Mechanical Engineering ETDs

In the present study, the feasibility of chemical modification of electron-irradiated Kapton is investigated. Characterization techniques determined the changes between a pristine, electron irradiated, and a chemically treated, i.e., fluorinated, sample of Kapton. Kapton is a common material in space application as it serves as the exterior surface for space vehicles. Highly aged Kapton have significant material property changes, making them prone to electro-static discharge (ESD) damage. Understanding how Kapton material behaves under space conditions and the possibility of improving its structure and properties is of utmost important. To this end, changes to the physical properties of the material were …

Characterization Of Single- And Multi-Phase Shock-Accelerated Flows, Patrick John Wayne

Mechanical Engineering ETDs

Experiments conducted in the Shock Tube Facility at the University of New Mexico are focused on characterization of shock-accelerated flows. Single-phase (gaseous) initial conditions consist of a heavy gas column of sulfur hexafluoride seeded with approximately 11% acetone gas by mass. Visualization of the image plane for gaseous initial conditions is accomplished via planar laser-induced fluorescence (PLIF) with a high-powered Nd:YAG ultraviolet laser and an Apogee Alta U-42 monochrome CCD camera, with a quantum efficiency > 90%. Multi-phase (gas-solid) initial conditions consist of glass micro-beads deposited on small 1-cm diameter discs of specific surface chemistry, mounted flush with the bottom wall …

Detection And Classification Of Vibrating Objects In Sar Images, Francisco German Perez Venegas

Electrical and Computer Engineering ETDs

The vibratory response of buildings and machines contains key information that can be exploited to infer their operating conditions and to diagnose failures. Furthermore, since vibration signatures observed from the exterior surfaces of structures are intrinsically linked to the type of machinery operating inside of them, the ability to monitor vibrations remotely can enable the detection and identification of the machinery.

This dissertation focuses on developing novel techniques for the detection and M-ary classification of vibrating objects in SAR images. The work performed in this dissertation is conducted around three central claims. First, the non-linear transformation that the micro-Doppler return …

A Transient Thermal And Structural Analysis Of Fuel In The Annular Core Research Reactor, Elliott Pelfrey

Mechanical Engineering ETDs

The health of a nuclear reactor’s fuel is essential to the operational longevity of the reactor. The health of the fuel in the Annular Core Research Reactor (ACRR) is a topic of increased interest due to both a proposed new facility that would include the ACRR and the recent resurfacing of contradictory reports regarding thermal stresses in its fuel pellets. Unlike other reactor fuels, which are widely used and well-characterized, the fuel in the ACRR is unique. The ACRR’s fuel elements consist of UO­₂-BeO fuel pellets, fluted niobium refractory liners, and stainless-steel cladding. The purpose of this thesis …

Direct Numerical Simulation Of Incompressible Spatially Developing Turbulent Mixing Layers, Juan Diego Colmenares Fernandez

Mechanical Engineering ETDs

Turbulent mixing layers are a canonical free shear flow in which two parallel fluid streams of different velocities mix at their interface. Understanding spatial development of a turbulent mixing layer is essential for various engineering applications. However, multiple factors affect physics of this flow, making it difficult to reproduce results in experiments and simulations. The current study investigates sensitivity of direct numerical simulation (DNS) of such a flow to computational parameters. In particular, effects of the computational domain dimensions, grid refinement, thickness of the splitter plate, and the laminar boundary layer characteristics at the splitter plate trailing edge are considered. …

The Influence Of Process Variables On Physical And Mechanical Properties In Laser Powder Bed Fusion, Joshua Robert Koepke, Bradley Jared, Yu-Lin Shen

Mechanical Engineering ETDs

Laser powder bed fusion additive manufacturing consists of a process that incorporates many process variables into fabricating parts. This study investigated several of these process variables and determined their influence on part properties. The process variables investigated include laser power, velocity, focus offsets, layer thickness, and powder particle size. Physical properties will be compared including surface roughness, form, and density. Tensile testing provided mechanical properties including unloading Young’s modulus, ultimate tensile strength, yield strength, uniform elongation, and ductility. Process maps will be developed that will provide recommendations for these process settings. It will be shown that these laser settings can …

Gaussian Process Regression Applied To Marine Energy Turbulent Source Tuning Via Metamodel Machine Learning Optimization, Sterling Olson

Mechanical Engineering ETDs

Converting energy from the currents found within tidal channels, open ocean, rivers, and canals is a promising yet untapped source of renewable energy. In order to permit current energy converters for installation in the environment, the CECs must be shown to non-negatively impact the environment. While developing these model increased utility may be gained if researchers may optimize mechanical power while constraining environmental effects. Surrogate models have garnered interest as optimization tools because they maximize the utility of expensive information by building predictive models in place of computational or experimentally expensive model runs. Marine hydrokinetic current energy converters require large-domain …

Investigation Of The Coupled Nuclear, Thermal-Hydraulic, And Thermomechanical Response Of A Natural Circulation Research Reactor Under Severe Reactivity-Initiated Accident Transients, Darren G. Talley

Mechanical Engineering ETDs

Research reactors play an important role in higher education, scientific research, and medical radioisotope production around the world. It is thus important to ensure the safety of facility workers and the public. This work presents a new reactor transient analysis code, referred to as Razorback, which computes the coupled reactor kinetics, fuel element heat transfer, fuel element thermal expansion and thermal stress, and thermal-hydraulic response of a natural circulation research reactor. The code was developed for the evaluation of large rapid reactivity addition in research reactors, with an initial focus on the Annular Core Research Reactor (ACRR) at Sandia National …

Adding Semi-Structured Automated Grid Generation And The Menter-Shear Stress Turbulence Transport Model For Internal Combustion Engine Simulations To Novel Fem Lanl Combustion Codes, Brad Montgomery Philipbar

Mechanical Engineering ETDs

The addition of GridPro semi-structured, automated generation of grids for complex moving boundaries for combustion engine applications and the Menter Shear Stress Turbulent Transfer (SST) model are being developed by Los Alamos National Laboratory. The software is called Fast, Easy, Accurate, and Robust Continuum Engineering (FEARCE). In addition to improving the time and effort required to build complex grid geometry for turbulent reactive multi-phase flow in internal combustion engines, the SST turbulence model has been programmed into the Predictor Corrector Fractional-Step (PCS) Finite Element Method (FEM) for reactive flow and turbulent incompressible flow regime validation is performed. The Reynolds-Averaged Navier-Stokes …