Mechanical Engineering Commons^™

Modeling And Simulation Of The Thermoforming Process In Thermoplastic-Matrix Composite Materials, Philip M. Bean

Electronic Theses and Dissertations

Thermoplastic-matrix composite materials have unique advantages over traditional thermosets including faster processing, improved fracture toughness, and recyclability. These and other benefits have caused increasing interest in the use of these materials in both aerospace and automotive industries. Due to the differences in behavior, these materials require a different type of manufacturing process to thermoset matrix composites. This manufacturing process generally involves using pre manufactured tape-layers. These layers, containing both thermoplastic-matrix and fiber-reinforcement, are aligned to the desired orientation, and stacked up into a “tailored blank” using an automated tape layup machine. They are then heated to the thermoplastic melting temperature …

Metal Thin Film Stiffness Extraction Technique For Surface Acoustic Wave Filters, Travis R. Weismeyer

Electronic Theses and Dissertations

Accurate knowledge of the surface acoustic wave (SAW) properties propagating at the surface of a piezoelectric substrate with thin films, electrodes or temperature compensated films, is critical in SAW filter design to meet the target frequency response, power durability and performance prior to device fabrication. While reliable material constants exist for substrates such as LiNbO3 used in SAW filters, the absolute elastic constants associated with operational thin films used for electrodes or temperature compensation do not exist. Although the bulk values of the constituent materials are known, the composite film/substrate properties are difficult to predict since they depend strongly on …

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 developed. …

Reinventing The Wheel, Esther K. Unti, Ahmed Z. Shorab, Patrick B. Kragen, Adam M. Menashe

Mechanical Engineering

Reinventing the Wheel selected tires and designed wheels for the 2018 Cal Poly, San Luis Obispo Formula SAE combustion vehicle. Available tire options were evaluated for steady-state and transient performance as well as vehicle integration. A single-piece composite wheel with hollow spokes was designed to meet stiffness, strength, and tolerance requirements. A detailed study of wheel loading and geometric structural efficiency was performed. Finite element analysis was used to iterate the geometry and laminate. A two-piece male mold was designed and machined to manufacture the wheel. Removable silicone inserts were used to create the hollow spokes.

Process-Property-Microstructure Relationships In Laser-Powder Bed Fusion Of 420 Stainless Steel., Subrata Deb Nath

Electronic Theses and Dissertations

Laser-powder bed fusion (L-PBF) is an additive manufacturing technique for fabricating metal components with complex design and customized features. However, only a limited number of materials have been widely studied using L-PBF. AISI 420 stainless steel, an alloy with a useful combination of high strength, hardness, and corrosion resistance, is an example of one such material where few L-PBF investigations have emerged to date. In this dissertation, L-PBF experiments were conducted using 420 stainless steel powders to understand the effects of chemical composition, particle size distribution and processing parameters on ensuing physical, mechanical and corrosion properties and microstructure in comparison …

In Silico Analysis Of Advanced Processing Methods For Light-Weight Alloys Powders, Marjan Nezafati

Theses and Dissertations

Light-weight Al and Mg-based metal-matrix nanocomposites (MMNCs) are lauded as one of the most promising structural materials for vehicle, military, and construction applications. These MMNCs are often synthesized using the powder metallurgy (PM) process under liquid nitrogen cryogenic environments to control the grain sizes. It is believed that proper incorporation of the nitrogen species into the bulk lattice during processing could strongly enhance the mechanical properties of MMNCs by forming N-rich dispersoids. In this work, using the density-functional theory (DFT), the adsorption, absorption and diffusion behavior of nitrogen molecule/atoms have been studied and related to t Al and Mg MMNC …

Optimization Of The Practice Of Slow Cooling Steel Bars: A Redesign And Modernization Of Materials, Eryn Johnston

Mechanical Engineering Undergraduate Honors Theses

Throughout the process of steel making, certain grades of steel are a higher risk for defects caused by the inability to quickly diffuse hydrogen through the steel when cooled to room temperature at a normal rate based on the ambient air temperature. To reduce the hydrogen flaking defects that are caused due to hydrogen entrapment in the steel, the process of slow cooling is utilized. This process reduces the cooling rate of steel bars by keeping them at a higher temperature for extended periods and in turn gives the hydrogen a chance to fully dissipate from the steel. In many …

Low Temperature Desiccants In Atmospheric Water Generation., Sunil Gupta

Electronic Theses and Dissertations

Surging global water demand as well as changes to weather patterns and over exploitation of natural water sources, such as ground water, has made potable water a critical resource in many parts of the World already – one rapidly heading towards a crisis situation. Desalination has been adopted as a solution – this is however energy intensive and impractical for most of the developing countries - those most in need of water. A renewable source of energy is solar thermal and solar photovoltaic. A plentiful source of water is the humidity in the atmosphere. This research is to push the …

Comparative Study Of Power Semiconductor Devices In A Multilevel Cascaded H-Bridge Inverter, Kenneth Mordi

Graduate Theses and Dissertations

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET …

A Systematic Investigation Of Condensation Heat Transfer Using Asymmetric Micro-Scale Surfaces, Emily Brown

LSU Master's Theses

Asymmetric surfaces been shown to inducing unidirectional motion in the Leidenfrost regime; however, very minimal research has been conducted to investigate whether these surface can enhance condensation through the same means. The investigation of heat transfer of ratchets in condensation is a relatively untapped area of study, specifically ratchets with superhydrophobic properties. Anticipated difficulty lies in creating surfaces features or coatings that retain the ratchets and can adequately sustain optimal wetting state of Cassie-Baxter required to improve heat transfer performance during condensation. This study serves to investigate whether ratchets are a feasible surface feature to enhance condensation heat transfer. First, …

Novel Design And Synthesis Of Composite Nanomaterials For Lithium And Multivalent Ion Batteries, Wangwang Xu

LSU Doctoral Dissertations

Nowadays, the fast-increasing energy demand for efficient, sustainable and environmentally-friendly energy storage devices remains a significant and challenging issue. Lithium ion batteries (LIBs) have been widely used as commercial energy devices in portable electronics and also shown great promise in upcoming large-scale applications due to their advantages of environmental safety, efficiency in energy delivering and light weight. However, due to their limited capacity, energy densities and cycle ability, LIBs still need further improvement to expand their applications to a larger field, especially electric vehicle (EVs) and hybrid electric vehicles (HEVs), in which energy storage devices with large capacity and high …

Hyperspectral Imaging For Characterizing Single Plasmonic Nanostructure And Single-Cell Analysis, Nishir Sanatkumar Mehta

LSU Master's Theses

Orientation of plasmonic nanostructures is an important feature in many nanoscale applications such as photovoltaics, catalyst, biosensors DNA interactions, protein detections, hotspot of surface-enhanced Raman spectroscopy (SERS), and fluorescence resonant energy transfer (FRET) experiments. Silver nanocubes with significant spectral signatures between 400-700 nm are observed in this experimental research. Whereas study of single cells will enable the analysis of cell-to-cell variations within a heterogeneous population. These variations are important for further analysis and understanding of disease propagation, drug development, stem cell differentiation, embryos development, and how cells respond to each other and their environment. Adipose-derived mesenchymal stem cells possess the …

Graphene-Based Lubrication For Tribological Applications: Nanolubricants And Self-Lubricating Nanocomposites, Emad Omrani

Theses and Dissertations

In this work, the effects of graphene nanoplatelets (GNPs) additives on tribological properties of aluminum are investigated. The objective of this research is to investigate and explain the enhancement mechanisms of GNPs at the contact surface during tribological testing. The graphene nanoplatelets are studied both as an oil additive (Chapter I) and as a reinforcement (Chapter II) experimentally. The coefficient of friction (COF) and wear rate were identified using a pin-on-disk test setup.

Mineral, organic, and synthetic oils are not always efficient enough to satisfy the demands of a high-performance lubricant; therefore, mixing additives with base fluids is an approach …

Incorporation Of Silica Nanoparticles Into The Underlayer Of Pda/Ptfe Thin Coatings, Adedoyin Abe

Mechanical Engineering Undergraduate Honors Theses

Polytetrafluoroethylene (PTFE) is one of the most low friction and corrosion resistant solid lubricants. Prior studies have shown that a polydopamine (PDA) underlayer enhances the durability of PTFE thin coating. In this study, 100, 200, and 300 µL of aqueous silica nanoparticle (NP) solutions were added to the PDA deposition solution. The durability and coefficient of friction of PDA/PTFE thin coatings on stainless steel substrates are investigated with and without incorporating the silica NPs. The coatings were tested in dry contact conditions using a Universal Mechanical Tester (UMT) with a ball-on-flat configuration in a reciprocating motion. It was found that …

Design Survey Of Laminated Composite I-Beam, Mrinmoy Saha

All Graduate Plan B and other Reports, Spring 1920 to Spring 2023

Composite I-beams are popular for high-strength low-weight applications. Learning the macro-mechanics and designing the composite I-beam properly are necessary. In this report, a design overview of the composite I-beam is discussed which is based on classical lamination theory where it includes the homogenization approach, the plane stress assumption and the Kirchhoff hypothesis. Using these assumptions, a method was developed to come up with the effective material properties of a beam. Formulas to calculate maximum deflection and maximum bending stress and shear stress and the stress concentration at the connection of web-flange are discussed which describe ways for designing and manufacturing …

Microstructure And Mechanical Properties Of Selective Laser Melted Superalloy Inconel 625., Md Ashabul Anam

Electronic Theses and Dissertations

Selective Laser Melting (SLM), a powder based Additive Manufacturing (AM) process, has gained considerable attention in the aerospace, biomedical and automotive industries due to its many potential benefits, such as, capability of fabricating complex three-dimensional components, shortened design to product time, reduction in process steps, component mass reduction and material flexibility. This process uses metallic powder and is capable of fabricating complex structures with excellent microstructure which make SLM not only an improvement over other manufacturing processes but also innovative material processing technology. Inconel 625, a nickel-based super alloy is widely popular in aerospace, chemical and nuclear industries. This alloy …

High Dynamic Range Optical Devices And Applications., Elijah Robert Jensen

Electronic Theses and Dissertations

Much of what we know about fundamental physical law and the universe derives from observations and measurements using optical methods. The passive use of the electromagnetic spectrum can be the best way of studying physical phenomenon in general with minimal disturbance of the system in the process. While for many applications ambient visible light is sufficient, light outside of the visible range may convey more information. The signals of interest are also often a small fraction of the background, and their changes occur on time scales so quickly that they are visually imperceptible. This thesis reports techniques and technologies developed …

Modeling And Validations Of Control Parameters For Material Extrusion-Based Additive Manufacturing Of Thixotropic Aluminum Alloys., Lars Herhold

Electronic Theses and Dissertations

Additive Manufacturing (AM) with metals has been accomplished mainly through powder bed fusion processes. Initial experiments and simulations using Material Extrusion Additive Manufacturing (MEAM) have been performed by various researchers especially using low melting alloys. Recently Stratasys Inc. submitted a patent application for the use of their Material Extrusion technology also called Fused Deposition Modeling (FDM) where they describe the process using thixotropic semi-solid alloys. Currently this process using semi-solid, engineering type alloys such as A356 or THIXALLOY 540 aluminum have not been researched to evaluate the control parameters. This research combines the in-depth knowledge of applying thixotropic semi-solid aluminum …

High Strain Rate Dynamic Response Of Aluminum 6061 Micro Particles At Elevated Temperatures And Varying Oxide Thicknesses Of Substrate Surface, Carmine Taglienti

Masters Theses

Cold spray is a unique additive manufacturing process, where a large number of ductile metal micro particles are deposited to create new surface coatings or free-standing structures. Metallic particles are accelerated through a gas stream, reaching velocities of over 1 km/s. Accelerated particles experience a high-strain-rate microscopic ballistic collisions against a target substrate. Large amounts of kinetic energy results in extreme plastic deformation of the particles and substrate. Though the cold spray process has been in use for decades, the extreme material science behind the deformation of particles has not been well understood due to experimental difficulties arising from the …

Effects Of Automated Fiber Placement On High Strain Rate Compressive Response Of Advanced Composites, Alexander Trochez

Mechanical & Aerospace Engineering Theses & Dissertations

Automated Fiber Placement (AFP) technology shows great promise in manufacturing carbon fiber composite structures. However, intermittent defects occur in the process that can affect the overall mechanical performance of the structure. The aim of this work is to investigate the effects of deliberately placed principal defects (Gap, Overlap, and Fold) on the compressive response under quasistatic (strain rate ~10^-3 s^-1) and dynamic (strain rate ~10³ s-1) loading conditions. The controlled defects were placed at the laminate level in different orientations and depths. High strain rate compression experiments were conducted using a split Hopkinson pressure bar (SHPB) …

Microstructural Characterization Of Shear Transformation Zones And Modeling Indentation Size Effect In Amorphous Polymers, Leila Malekmotiei

LSU Doctoral Dissertations

The first aim of this work is developing a procedure for experimental and analytical characterization of nano-scale microstructures which mediate large scale deformation in amorphous polymers. Glassy polymers are extensively used as high impact resistant, low density, and clear materials in industries. Nevertheless, their response under severe loading conditions is yet to be appropriately unraveled. Due to the lack of long-range order in the microstructures of glassy solids, their plastic deformation is different from that in crystalline solids. Shear Transformation Zones (STZs) are believed to be the main plasticity carriers in amorphous solids and defined as the localized atomic or …

Effect Of Material Viscoelasticity On Frequency Tuning Of Dielectric Elastomer Membrane Resonators, Liyang Tian

Electronic Thesis and Dissertation Repository

Dielectric elastomers (DEs) capable of large voltage-induced deformation show promise for applications such as resonators and oscillators. However, the dynamic performance of such vibrational devices is not only strongly affected by the nonlinear electromechanical coupling and material hyperelasticity, but also significantly by the material viscoelasticity. The material viscoelasticity of DEs originates from the highly mobile polymer chains that constitute the polymer networks of the DE. Moreover, due to the multiple viscous polymer subnetworks, DEs possess multiple relaxation processes. Therefore, in order to predict the dynamic performance of DE-based devices, a theoretical model that accounts for the multiple relaxation processes is …

Analysis Of The Low-Cycle Fatigue Behavior Of Silicone Rubber For Biomedical Balloons, Chase Cooper

Materials Engineering

The development of a medical drug delivery device that allows for the deployment drugs into the adventitial tissue of blood vessels requires the inflation of a silicone elastomer. The inflated silicone must be able to consistently endure multiple loading cycles without failing so that the device can operate reliably. There are multiple methods of processing the silicone for the device and the goal of this study is to examine the effect of the various processing methods on the characteristics of the silicone. The Dynamic Mechanical Analysis Machine (DMA) is used to model the conditions of the device’s application by performing …

Composite Suspension For A Mass Market Vehicle, Sarah M. Chapiama, Brian Auyeung, Jose Guerrero, Ethan Lau

Mechanical Engineering

Statement of Confidentiality: The complete senior project report was submitted to the project advisor and sponsor. The results of this project are of a confidential nature and will not be published at this time.

Mechanical Characterization Of Selectively Laser Melted 316l Stainless Steel Body Centered Cubic Unit Cells And Lattice Of Varying Node Radii And Strut Angle, Christopher James Hornbeak

Master's Theses

An experimental study of several variants of radius and strut angle of the body centered cubic unit cell was performed to determine the mechanical properties and failure mechanisms of the mesostructure. Quasi static compression tests were performed on an Instron® universal testing machine with a 50kN load cell at 0.2mm/min. The test samples were built using a SLM Solutions 125 selective laser melting machine with 316L stainless steel. Test specimens were based on 5mm cubic unit cells, with a strut diameter 10% of the unit cell size, with skins on top and bottom to provide a cantilever boundary constraint. Specimens …

Perovskite Solar Cells Fabricated Via Scalable Dip Coating Methods, Joseph F. Iannello

Theses and Dissertations

Perovskite solar cells present the possibility for less expensive electricity generation, through the use of low cost materials and fabrication methods relative to current silicon-based technology. Many current methods of fabricating thin film perovskite solar cells focus on spin-coating, which inherently lacks scalability due to particle conglomeration, poor uniformity over a larger area, and safety concerns. Dip-coating, an alternative to spin-coating, which is explored here addresses these issues which limit scalability. Each individual layer can be separately synthesized, deposited, and characterized, which leads towards scalability. Choosing only the best results from each independent layer allowed progress to the creation of …

Soft-Microrobotics: The Manipulation Of Alginate Artificial Cells, Samuel Sheckman

Mechanical Engineering Research Theses and Dissertations

In this work, the approach to the manipulation of alginate artificial cell soft-microrobots, both individually and in swarms is shown. Fabrication of these artificial cells were completed through centrifugation, producing large volumes of artificial cells, encapsulated with superparamagnetic iron oxide nanoparticles; these artificial cells can be then externally stimulated by an applied magnetic field. The construction of a Permeant Magnet Stage (PMS) was produced to manipulate the artificial cells individually and in swarms. The stage functionalizes the permanent magnet in the 2D xy-plane. Once the PMS was completed, Parallel self-assembly (Object Particle Computation) using swarms of artificial cells in complex …

Preliminary Investigation Of Tensile Strength And Impact Characterization Of Cementitious Composite Incorporating Carbon Nanotubes, Robabeh Jazaei

UNLV Theses, Dissertations, Professional Papers, and Capstones

Cement has been largely used in the construction industry, specifically as a matrix for concrete. Recently, a new generation of cement-based composite that greatly increases mechanical properties is replacing conventional concrete. With periodic advances in the field, researchers considered particles with high-aspect ratios such as Carbon Nanotubes (CNTs) to reinforce cement matrices. Although there is not much literature to draw upon in research, some research on improving the tensile strength of cementitious composite incorporating with CNTs does exist. However, there had been no evidence of investigation into impact strength until this study.

Most papers presented examined the effect of multi-walled …

Design And Synthesis Of Novel Nanometallic Catalysts And Electrode Materials For Green Fuel Cells, Jing Zhang

Graduate Dissertations and Theses

The United Nations formally adopted 17 sustainable development goals (SDGs) at its 2015 summit. Many of these goals addressed issues such poverty, hunger, health, education, climate-change, gender equality, water, sanitation, energy, urbanization, environment and social justice. The seventh SDG seeks to ensure access to affordable, reliable, sustainable and modern energy for all. So among all renewable forms of energy, fuel cells with high efficiency have attracted a lot of attention recently. In particular, the direct ethanol fuel cells (DEFCs) and microbial fuel cells (MFCs) are significant due to their green fuel, less waste generated and environmental friendliness. Hence the overall …

Effects Of Tension On Resonant Frequencies Of Strings, Blake Burnett

Senior Theses

This project tests and explores resonance of strings. Since all materials and mechanisms are affected by vibrations, it is important to know the frequencies at which resonance occurs. To explore this subject, strings were used as a model material to test the effect tension has on resonance. The fundamental frequencies and the corresponding modes of resonance were used to analyze the data. The results of this experiment show that increasing tension on a string increases its resonance frequency. Understanding the physics behind resonance frequency allows systems to be designed to take advantage of resonance properties, or to avoid resonance where …