Mechanical Engineering Commons^™

Fabrication Of Multi-Material Structures Using Ultrasonic Consolidation And Laser-Engineered Net Shaping, John Olorunshola Obielodan

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

This research explores the use of two additive manufacturing processes for the fabrication of multi-material structures. Ultrasonic consolidation (UC) and laser- engineered net shaping (LENS) processes were used for parallel systematic investigations of the process parameters and methodologies for the development of multi-material structures.

The UC process uses ultrasonic energy at low temperature to bond metallic foils. A wide range of metallic materials including nickel; titanium; copper; molybdenum; tantalum; MetPreg®; silver; stainless steel; and aluminum alloys 1100, 3003, and 6061 were bonded in different combinations. Material domains are inherently discrete in ultrasonically consolidated structures. The mechanical properties of some of …

Spatial Light Dilution As A Technique For Conversion Of Solar Energy To Algal Biomass, Daniel J. Dye

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A photobioreactor has been designed and developed to efficiently utilize solar irradiance through spatial dilution of sunlight. The concept of spatial light dilution is simple: incident sunlight is spread over a large surface area, thus reducing the photon flux density of the light. The implementation of this technique, however, is difficult. The reactor described within uses a new approach to spatial light dilution, utilizing recently-developed optical components to diffuse concentrated sunlight inside an algae culture. Preliminary productivity tests indicate a 2-3 fold increase in productivity per unit aperture (sunlight collection area) over a control reactor with direct-sunlight. Aperture productivity of …

Integration Of Ultrasonic Consolidation And Direct-Write To Fabricate An Embedded Electrical System Within A Metallic Enclosure, Ludwing A. Hernandez

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A research project was undertaken to integrate Ultrasonic Consolitation (UC) and Direct-Write (DW) technologies into a single apparatus to fabricate embedded electrical systems within an ultrasonically consolidated metallic enclosure. Process and design guidelines were developed after performing fundamental research on the operational capabilities of the implemented system. In order to develop such guidelines, numerous tests were performed on both UC and DW. The results from those tests, as well as the design and process guidelines for the fabrication of an embedded touch switch, can be used as a base for future research and experimentation on the UC-DW apparatus. The successful …

Axisymmetric Finite Element Modeling For The Design And Analysis Of Cylindrical Adhesive Joints Based On Dimensional Stability, Paul E. Lyon

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The use and implementation of adhesive joints for space structures is necessary for incorporating fiber-reinforced composite materials. Correct modeling and design of cylindrical adhesive joints can increase the dimensional stability of space structures. The few analytical models for cylindrical adhesive joints do not fully describe the displacement or stress field of the joint.

A two-dimensional axisymmetric finite element model for the design and analysis of adhesive joints was developed. The model was developed solely for the analysis of cylindrical adhesive joints, but the energy techniques used to develop the model can be applied to other types of joints as well. …

Toward The Validation Of Depth-Averaged, Steady-State Simulations Of Fluvial Flows Using Three-Dimensional, Steady-State, Rans Turbulence Models, Pedro Abdiel Mateo Villanueva

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Calculations of fluvial flows are strongly influenced by geometry complexity and large overall uncertainty on every single measurable property, such as velocity and shear. Moreover, a considerable portion of the data obtained from computational simulations arose from two-dimensional, steady-state models. The present work states a different approach to perform computer-based simulations and analyze fluvial flows. For the first part, the suitability of OpenFOAM to be used as the main CFD solver to analyze fluvial flows is studied. Initially, two well documented channel configurations are computationally studied using OpenFOAM. Finally, these results are compared to the output obtained from one of …

Triso Fuel Compact Thermal Conductivity Measurement Instrument Development, Colby Jensen

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Thermal conductivity is an important thermophysical property needed for effectively predicting fuel performance. As part of the Next Generation Nuclear Plant (NGNP) program, the thermal conductivity of tri-isotropic (TRISO) fuel needs to be measured over a temperature range characteristic of its usage. The composite nature of TRISO fuel requires that measurement be performed over the entire length of the compact in a non-destructive manner. No existing measurement system is capable of performing such a measurement.

A measurement system has been designed based on the steady-state, guarded-comparative-longitudinal heat flow technique. The system as currently designed is capable of measuring cylindrical samples …

Plasticity And Damage In Bimodal Grain Size Al-5083: Microstructural Finite Element, Steven Nelson

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Bimodal and nanocrystalline aluminum alloys are being investigated as stronger replacements for conventional polycrystalline aluminum alloys. Higher strengths are achieved by reducing the grain size of a metal; however, as the grain size is reduced the ductility diminishes. One solution that limits this decrease in ductility is the addition of a few microcrystalline grains into a nanocrystalline alloy, creating a bimodal microstructure that offers a better balance of strength and ductility. Two- and three-dimensional microstructural finite element (FE) simulations of monotonic and fatigue failures in Al-5083 having bimodal grain structures are conducted. To reduce the computational time and facilitate the …

Support Materials Development And Integration For Ultrasonic Consolidation, Matthew L. Swank

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Support materials play a vital role across the entire field of additive manufacturing (AM) technologies. They are essential to provide the ability to create complex structures and features using AM. Successful implementation of support materials in ultrasonic consolidation (UC) will provide a vast opportunity for improvement of geometric complexity. Experimentation was performed to evaluate suitable support materials and their effectiveness within UC. Additionally a fused deposition modeling (FDM) system was integrated into the UC build environment to create an automated support deposition system. Finally several unique structures were built using support materials to demonstrate the improved geometric capability and to …

Fatigue Life Analysis Of T-38 Aileron Lever Using A Continuum Damage Approach, James D. Gyllenskog

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In a recent investigation conducted by the United States Air Force, the mechanical failure of the aileron lever, manufactured from 2014-T6 aluminum, caused the fatal mishap of a T-38 trainer aircraft. In general the locations of cracks are unknown and must be determined by simulation. In this study we propose to use a continuum damage modeling approach to determine the degradation and damage in a material as the number of cycles of loading increases. This approach successfully predicts the location of crack initiation, propagation path, and propagation rate. A stress-based model in conjunction with the successive initiation technique is utilized. …

Thermo-Mechanical Reliability Of Micro-Interconnects In Three-Dimensional Integrated Circuits: Modeling And Simulation, Omar Rodriguez

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Three-dimensional integrated circuits (3D ICs) have been designed with the purpose of achieving higher communication speed by reducing the interconnect length between integrated circuits, and integrating heterogeneous functions into one single package, among other advantages. As a growing, new technology, researchers are still studying the different parameters that impact the overall lifetime of such packages in order to ensure the customer receives reliable end products. This study focused on the effect of four design parameters on the lifetime of the interconnects and, in particular, solder balls and through-silicon vias (TSVs). These parameters included TSV pitch, TSV diameter, underfill stiffness and …

Design And Scale-Up Of Production Scale Stirred Tank Fermentors, Ryan Z. Davis

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

In the bio/pharmaceutical industry, fermentation is extremely important in pharmaceutical development, and in microbial research. However, new fermentor designs are needed to improve production and reduce costs of complex systems such as cultivation of mammalian cells and genetically engineered micro-organisms. Traditionally, stirred tank design is driven by the oxygen transfer capability needed to achieve cell growth. However, design methodologies available for stirred tank fermentors are insufficient and many times contain errors. The aim of this research is to improve the design of production scale stirred tank fermentors through the development of dimensionless correlations and by providing information on aspects of …

Guidance And Navigation Linear Covariance Analysis For Lunar Powered Descent, Travis J. Moesser

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A linear covariance analysis is conducted to assess closed-loop guidance, navigation, and control system (GN&C) performance of the Altair vehicle during lunar powered descent. Guidance algorithms designed for lunar landing are presented and incorporated into the closed-loop covariance equations. Navigation-based event triggering is also included in the covariance formulation to trigger maneuvers and control dispersions. Several navigation and guidance trade studies are presented demonstrating the influence of triggering and guidance and study parameters on the vehicle GN&C performance.

In-Pile Thermal Conductivity Measurement Methods For Nuclear Fuels, Brandon S. Fox

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Measuring nuclear fuel thermal conductivity in-pile can provide much needed data for understanding fuel performance during irradiation and yield thermophysical property data needed for simulation codes and fuel databases. The objective of this research is to develop and compare two in-pile thermal conductivity methods in a laboratory setting using surrogate fuel materials.

A steady-state radial heat flow method was investigated to understand its viability as an in-pile steady-state thermal conductivity technique. By using Joule heating to simulate volumetric heat generation within a surrogate fuel rod, thermal conductivity was measured with two thermocouples at different radial positions within the rod. Examinations …

Mathematical Modeling Of Light Utilization And The Effects Of Temperature Cycles On Productivity In A Steady-State Algal Photobioreactor, Peter Edwin Zemke

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

The work presented here investigated two methods of improving productivity in microalgal photobioreactors: applying temperature cycles intended to maximize photosynthesis and minimize respiration, and development of a mathematical model that predicts improvements in photon utilization using temporal light dilution (flashing).

The experiments conducted on diurnal temperature cycles with Dunaliella tertiolecta in 30-L outdoor photobioreactors showed that a properly chosen temperature cycle can improve mass and energy productivity by 18% over an identical photobioreactor with a constant temperature. However, excessively large temperature cycle amplitudes reduced productivity. A 4-7% increase in energy content was observed in microalgae exposed to temperature cycles. The …

A Study On Stainless Steel 316l Annealed Ultrasonic Consolidation And Linear Welding Density Estimation, Raelvim Gonzalez

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ultrasonic Consolidation of stainless steel structures is being investigated for potential applications. This study investigates the suitability of Stainless Steel 316L annealed (SS316L annealed) as a building material for Ultrasonic Consolidation (UC), including research on Linear Welding Density (LWD) estimation on micrographs of samples. Experiment results are presented that include the effect of UC process parameters on SS316L annealed UC, optimum levels of these parameters, and bond quality of ultrasonically consolidated SS316L annealed structures in terms of LWD. In support to these efforts, a Measurement System Analysis for LWD assessment has been performed, and a new instrument for LWD measurement …

Effects Of Temperature And Humidity On Glass-Reinforced Nylon Rotating Bands, Marc D. Raby

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Certain 30mm munitions used in various military applications are configured with a glass-reinforced nylon band that acts as a firing ring or rotating band. The purpose of this research is to investigate whether storage environments compromise the strength and integrity of the glass-reinforced nylon rotating bands by researching the environmental factors that will degrade nylon and by performing tests to investigate if these factors will embrittle nylon composites. Moisture and temperature are found to be the environmental factors that will have an effect on the rotating bands in their respective storage environments. Absorbed moisture is found to increase the impact …

Experiment And Simulation On The Dynamics Of A Slug Of Liquid Oxygen Displaced By A Pulsed Magnetic Field, Jeffrey C. Boulware

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

A magnetic fluid system could potentially replace mechanically moving parts in a satellite as a means of increasing system reliability and mission lifetime, but rather than a standard ferrofluid with magnetic particles, liquid oxygen (LOX) may be a more adequate working fluid. As a pure paramagnetic cryogen, LOX is already heavily used in space, but still requires basic research before being integrated into system development. The objectives of the research conducted were to verify LOX as a magnetic working fluid through experiment and establish a theoretical model to describe its behavior. This dissertation presents the theoretical, experimental, and numerical results …