Open Access. Powered by Scholars. Published by Universities.®

Digital Commons Network

Open Access. Powered by Scholars. Published by Universities.®

Articles 1 - 30 of 85

Full-Text Articles in Entire DC Network

Optimal Control Strategies For Complex Biological Systems, Afroza Shirin Aug 2019

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 ...


Post-Polymerization Modification Of Kapton Using Electron Beam Irradiation, Luis A. Hernandez Jul 2019

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 ...


Characterization Of Single- And Multi-Phase Shock-Accelerated Flows, Patrick John Wayne Jul 2019

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 ...


Detection And Classification Of Vibrating Objects In Sar Images, Francisco German Perez Venegas Apr 2019

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 Apr 2019

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 ...


Direct Numerical Simulation Of Incompressible Spatially Developing Turbulent Mixing Layers, Juan Diego Colmenares Fernandez Apr 2019

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 Apr 2019

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 ...


Gaussian Process Regression Applied To Marine Energy Turbulent Source Tuning Via Metamodel Machine Learning Optimization, Sterling Olson Apr 2019

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 Mar 2019

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 Jan 2019

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 ...


Stability Of A Spinning Triangle Tethered Spacecraft System In A Circular Orbit, Matthew James Heitstuman Dec 2018

Stability Of A Spinning Triangle Tethered Spacecraft System In A Circular Orbit, Matthew James Heitstuman

Mechanical Engineering ETDs

Equations of motion are derived for a spinning triangle tethered spacecraft system and are used to analyze the stability of such systems. Floquet theory is applied to the linearized, periodic coefficient, equations of motion to analyze spin stability as a function of triangle geometry and the average spin rate of the satellite relative to the angular velocity of the spacecraft orbiting around a central body. The results of the Floquet analysis show that spin stability is achievable for many combinations of spacecraft geometry and spin rate. Spacecraft engineers or operators for a triangle-shaped tethered spacecraft can use this information for ...


Elevated Temperature Progressive Damage And Failure Of Duplex Stainless Steel, Darren P. Luke Dec 2018

Elevated Temperature Progressive Damage And Failure Of Duplex Stainless Steel, Darren P. Luke

Civil Engineering ETDs

Ductile failure of metals has been the focus of research efforts within academia and industry for many years since it is tremendously important for understanding the failure of structures under extreme loading conditions. However, limited research has been dedicated to elevated temperature ductile failure, which is critical for evaluating catastrophic events such as industrial, structural or shipping vessel fires. A detailed investigation was conducted on the structural response of Duplex Stainless Steel at elevated temperatures. The temperature dependence of elastic modulus, yield strength, ultimate strength, and ductility was measured up to 1000°C and a continuum damage plasticity model was ...


Integration Of A Commercial Smart Thermostat To The Aggregated Load Control Simulation Framework, Jee Won Choi Dec 2018

Integration Of A Commercial Smart Thermostat To The Aggregated Load Control Simulation Framework, Jee Won Choi

Mechanical Engineering ETDs

As part of an effort to achieve a better balance between the power demand and supply, load (demand) control simulation framework is previously developed. In the framework, HVAC load is used as a control resource, driven by the thermostat logic modeled within the framework. However, it has not been proved, whether a com- mercial thermostat is able to perform modeled thermostat’s features. Therefore, it is desired to integrate a commercial thermostat to the framework, to verify its capabil- ity of participating and performing the Demand Response (DR) scheme developed. A ‘Nest Learning Thermostat’ is selected as a commercial thermostat ...


Engineering Viscoelastic Behavior Of Carbon Fiber Reinforced Polymer Composites With Nanoparticles For Controlling Deployment Of Aerospace Structures, Mark Scherbarth Nov 2018

Engineering Viscoelastic Behavior Of Carbon Fiber Reinforced Polymer Composites With Nanoparticles For Controlling Deployment Of Aerospace Structures, Mark Scherbarth

Mechanical Engineering ETDs

The United States Air Force is focused on reducing mass and power consumption of spacecraft to increase their capabilities for space missions. Low mass and power consumption can be achieved by using composites with low density and high stiffness and utilizing few satellite components. One way to achieve reduced mass is by eliminating attendant deployment mechanisms consuming valuable power and mass allocations on spacecraft with deployable structures. Secondary systems are typically used to assist deployable space structures to ensure 100% success. A passively deployed space structure would be of great value to the Department of Defense and the commercial marketplace ...


Reducing Stress In 3d Printed Parts Made With Laser Engineered Net Shaping, Shaun Ross Whetten Apr 2018

Reducing Stress In 3d Printed Parts Made With Laser Engineered Net Shaping, Shaun Ross Whetten

Mechanical Engineering ETDs

Thermal cycling and repeated melting/solidification cycles characteristic of 3D metal printing processes causes buildup of residual stress in 3D printed parts. Using laser engineered net shaping (LENS®), residual stresses are formed leading to deformation and possible cracking of the 3D printed metal components. The LENS process offers opportunities for rapid prototyping, alternative manufacturing processes, and repair of worn/broken components so it is important to be able to minimize the effects of residual stress. Work was performed to understand the benefit of substrate heating on reducing residual stress in metal parts made using the LENS process. Substrate deformation, and ...


Fatigue Crack Modeling Of Additively Manufactured Abs Cantilever Beam, Jason W. Booher Apr 2018

Fatigue Crack Modeling Of Additively Manufactured Abs Cantilever Beam, Jason W. Booher

Mechanical Engineering ETDs

A Finite Element model was developed to model crack development in additively manufactured additively manufactured Acrylonitrile Butadiene Styrene (ABS) cantilever beams. Experiments were conducted on the beams with both shock and random vibration base excitations. The base excitations induced damage in the beam that cause crack propagation. It was observed during the cracks developmental stages that an increase in damping occurred. The proposed Finite Element model also showed similar increases in damping from the addition of Coulomb damping forces.


Co-Simulation Framework For Power Distribution System Analysis With Humans In The Loop, Victor H. Ayon Dec 2017

Co-Simulation Framework For Power Distribution System Analysis With Humans In The Loop, Victor H. Ayon

Mechanical Engineering ETDs

Recent developments in the area of power generation have led to an increased penetration of storage and distributed energy resources (DER) in power distribution systems. As a result, new and enhanced energy management systems will be necessary as the deployment of DERs, as well as the need to control loads, continues to increase in the coming years. Advanced management systems are especially important to achieve resilient power delivery during emergency situations. During a blackout for example, a section of a distribution feeder could island to operate as a microgrid to ensure critical services such as water, food, and medical care ...


Investigating Scalable Manufacturing Of High-Conductivity Wires And Coatings From Ultra-Long Carbon Nanotubes, Pouria Khanbolouki Nov 2017

Investigating Scalable Manufacturing Of High-Conductivity Wires And Coatings From Ultra-Long Carbon Nanotubes, Pouria Khanbolouki

Mechanical Engineering ETDs

Carbon nanotubes (CNTs) are a promising candidate for next generation of electrical wirings and electromagnetic interference (EMI) shielding materials due to their exceptional mechanical and electrical properties. Wires and coatings from ultralong nanotubes that are highly crystalline, well-aligned and densely packed can achieve this goal. High-performance CNT conductors will be relatively lightweight and resistant to harsh conditions and therefore can potentially replace current conductors in many industries including aerospace, automotive, gas and oil.

This thesis investigates a new manufacturing approach, based on conventional solution coating and wire drawing methods, to fabricate high conductivity wires and coatings from ultra-long carbon nanotubes ...


Effect Of Alignment, Sizing, And Manufacturing Method On Mechanical Properties Of Recycled Carbon Fiber Composites, Nekoda Van De Werken Nov 2017

Effect Of Alignment, Sizing, And Manufacturing Method On Mechanical Properties Of Recycled Carbon Fiber Composites, Nekoda Van De Werken

Mechanical Engineering ETDs

The exceptional combination of properties offered by carbon fiber composites has propelled their incorporation into high performance markets such as aerospace, wind energy, luxury cars and sporting goods. While the use of carbon fiber in these sectors is expected to continue to increase, the high price and energy cost associated with carbon fiber production acts as a significant barrier of entry into larger volume markets, such as the automotive industry. One method of navigating this transition is through the use of recycled carbon fiber composites.

Carbon fiber reclamation can produce fibers with up to 90% and 100% of the strength ...


Tensile Experimentation Of Structural Aluminum Studying Void Growth, Scott Gampert Nov 2017

Tensile Experimentation Of Structural Aluminum Studying Void Growth, Scott Gampert

Mechanical Engineering ETDs

Uni-axial tensile tests were conducted on multiple dog-bone shaped poly-crystalline Aluminum specimens. The goal for this study was to understand the effects of voiding in structural aluminum and how voids grow under tension. The voids were represented by simply drilling and reaming one or more holes in varying patterns in the center of the sample. The testing clearly showed that the different hole patterns affect the area growth of voids. It also compares the developmental growth of a plasticity zone around samples with one hole to a previous study done with a different specimen shape(Ray,2003). In order to ...


Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi Jul 2017

Evaluation And Enhancement Of Clean Energy Systems: Analytical, Computational And Experimental Study Of Solar And Nuclear Cycles, Nima Fathi

Mechanical Engineering ETDs

Clean (and specifically renewable) energy is steadily improving its global share. However, finite availability of fossil fuels and the growing effects of climate change make it an urgent priority to convince the industry and governments to incentivize investment in the renewable energy field and to make it more attractive by decreasing the capital cost. Until recently, uncertainties in funding limited renewable energy development, especially in the US. That limitation has been one of the barriers to progress. Another limitation of many renewable energy systems is the variability in their output, which makes them unsuitable for baseline power production. Therefore, fossil ...


A Thermodynamic Study Of Binary Real Gas Mixtures Undergoing Normal Shocks, Josiah M. Bigelow Jul 2017

A Thermodynamic Study Of Binary Real Gas Mixtures Undergoing Normal Shocks, Josiah M. Bigelow

Mechanical Engineering ETDs

We investigate the difference between Amagat and Dalton mixing laws for gaseous equations of state (EOS) using planar traveling shocks. Numerical modeling was performed in the Sandia National Laboratories hydrocode CTH utilizing tabular EOS in the SESAME format. Numerical results were compared to experimental work from the University of New Mexico Shock Tube Laboratory. Latin hypercube samples were used to assess model sensitivities to Amagat and Dalton EOS. We find that the Amagat mixing law agrees best with the experimental results and that significant difference exist between the predictions of the Amagat and Dalton mixing methods.


Characterizing The Viscoelastic Behavior Of Pdms/Pdps Copolymers, Mark E. Small Jun 2017

Characterizing The Viscoelastic Behavior Of Pdms/Pdps Copolymers, Mark E. Small

Mechanical Engineering ETDs

Viscoelasticity is the property of materials that exhibits both viscous and elastic characteristics when undergoing deformation. In polymeric materials, the mechani- cal behavior is dominated by this viscoelastic phenomenon. Creating computational models for these materials can be quite complicated due to their frequency depen- dent and temperature dependent material properties. The research presented in this paper will use state of the art methods to fully develop a material model for a filled polydimethylsiloxane-polydiphenynlsiloxane (PDMS/PDPS) copolymer foam that has yet to be characterized. Mechanical properties of PDMS/PDPS copoly- mers are currently being studied to assess engineering performance, and to ...


Evaluation Of Concrete Constitutive Models For Impact Simulations, Guillermo A. Mata Jun 2017

Evaluation Of Concrete Constitutive Models For Impact Simulations, Guillermo A. Mata

Mechanical Engineering ETDs

The research documented in this thesis deals with computational analysis of reinforced concrete impacted by both hollow and solid missiles as a continuing effort on the work conducted by the Committee on the Safety of Nuclear Installations (CSNI) and Nuclear Energy Agency (NEA). The analysis focuses on comparing two similar material models and their ability to capture the mechanistic response of a reinforced concrete slab subjected to impact loads. The analysis was performed using the Sandia National Laboratories computing software SIERRA Solid Mechanics to run the finite element model. The two constitutive models studied were the Holmquist-Johnson-Cook and Johnson-Holmquist 2 ...


An Experimental And Numerical Study Of Nanomechanical Behavior Of Hard/Soft Multilayered Coatings, Benigno Sandoval May 2017

An Experimental And Numerical Study Of Nanomechanical Behavior Of Hard/Soft Multilayered Coatings, Benigno Sandoval

Mechanical Engineering ETDs

Multilayer thin film composites, sometimes referred to as nanolaminates, have emerged as an important subset of materials with novel, and often tunable, properties such as high strength, high toughness, and resistance to wear or corrosion. Often fabricated using alternating layers of two or more materials, these multilayer thin film coatings are typically expensive and time intensive to fabricate and characterize and exhibit novel responses to nanomechanical testing such as plasticity during unloading. This thesis explores the nanoindentation response of hard/soft multilayer coatings through examination of the optical coating Al/SiC and similar coating Al/SiO2. Instrumented indentation was used ...


Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, Mohammad Reza Zamani Kouhpanji May 2017

Investigating The Classical And Non-Classical Mechanical Properties Of Gan Nanowires, Mohammad Reza Zamani Kouhpanji

Electrical and Computer Engineering ETDs

Study and prediction of classical and non-classical mechanical properties of GaN is crucial due to the potential application of GaN nanowires (NWs) in piezoelectric, probe-based nanometrology, and nanolithography areas. GaN is mainly grown on sapphire substrates whose lattice constant and thermal expansion coefficient are significantly different from GaN. These discrepancies cause mechanical defects and high residual stresses and strains in GaN, which reduce its quantum efficiency.

Specifically, for nanoscale applications, the mechanical properties of materials differ significantly compared to the bulk properties due to size-effects. Therefore, it is essential to investigate the mechanical properties of GaN NWs using the non-classical ...


Analytic Solutions For The Crack-Tip Plastic Zone Under Mixed Mode Loading Conditions, Jason Ivey May 2017

Analytic Solutions For The Crack-Tip Plastic Zone Under Mixed Mode Loading Conditions, Jason Ivey

Mechanical Engineering ETDs

Analytic solutions for the plastic region surrounding a crack tip are derived under mixed mode I/II and mixed mode I/II/III loading conditions for an elastic-plastic solid with a semi-infinite crack. Both the Von Mises and Tresca yield criteria are applied. Additionally, plane stress and plane strain assumptions are included when applicable. The results show a strong dependence on the ratio of the stress intensity factors for each loading mode. It is shown that the plastic zone area given by the Tresca yield criterion is larger than that given by the Von Mises yield criterion. Lastly, it is ...


Characterization Of A Small Electro-Mechanical Contact Using Non-Conventional Measurement Techniques, Kelsey M. Johnson Apr 2017

Characterization Of A Small Electro-Mechanical Contact Using Non-Conventional Measurement Techniques, Kelsey M. Johnson

Mechanical Engineering ETDs

Currently there are limitations in computing chatter behavior of small electrical contacts embedded in components using finite element models. Reduced order models (ROM) have been developed of such electrical contact sub-assemblies to assess the chatter behavior of the contacts during vibration and shock environments. The current ROM method requires experimental validation. This ROM also neglects the damping effects of the viscous fluid that typically surrounds such sub-assemblies. Dynamic ring-down testing of the electrical contacts in air was performed and will provide a validation data set for the current ROM. Additionally, dynamic ring-down testing of the electrical contact was performed in ...


The Mathematical Theory Of Deformation Arrest In Large-Strain Dynamic Plasticity, Brendan A. Kullback Apr 2017

The Mathematical Theory Of Deformation Arrest In Large-Strain Dynamic Plasticity, Brendan A. Kullback

Mechanical Engineering ETDs

Ductile structural components subjected to explosive loadings exhibit a large range of behaviors. The response of beams, walls, and blast doors is estimated using two methods. The engineering level approaches are highly simplified and neglect much of the relevant physics while the use of finite element or shock-code simulation is expensive and not suited to rapid problem solving and parameter studies. In this dissertation, a medium fidelity reduced order modeling approach has been derived to capture the most relevant physics governing rupture of ductile bodies dynamically deforming in tension.

Solution of the inertially stretching jet is used to reveal the ...


High-Throughput Tensile Testing Reveals Stochastic Properties In Additively Manufactured Steel, Bradley C. Salzbrenner Apr 2017

High-Throughput Tensile Testing Reveals Stochastic Properties In Additively Manufactured Steel, Bradley C. Salzbrenner

Mechanical Engineering ETDs

An adage within the Additive Manufacturing (AM) community is that “complexity is free”. Complicated geometric features that normally drive manufacturing cost and limit design options are not typically problematic in AM. While geometric complexity is usually viewed from the perspective of part design, this advantage of AM also opens up new options in rapid, efficient material property evaluation and qualification. This Thesis demonstrates how 100’s of miniature tensile bars can be produced and tested for comparable cost and in comparable time to a few conventional tensile bars. With this technique, it is possible to evaluate the stochastic nature of ...