Mechanics of Materials Commons^™

Micro-Mechanical Characterization Of Uhpc Stiffness Mechanisms: Towards A Better Understanding Of Concrete Elastic Modulus, Charissa N. Puttbach

Graduate Theses and Dissertations

Current design code equations for estimating the elastic modulus of specialty concretes like ultra-high performance concrete are not all suitable. Developing empirical curves from exhaustive experimental testing is challenging for concretes that may have high levels of cement replacement with mineral admixtures and fibers at varying volume contents. As such, an alternative approach is taken that seeks to understand the constituent microscale stiffness mechanisms and relate the results to the macroscale. Micropillars are fabricated on several cement paste phases using a focused ion beam. A modified pico-indenter is used to determine the linear and non-linear behavior under micro-compression loading. Micropillar …

Analysis Of Additively Manufactured Inconel 718 Combustion Behavior In Promoted Oxygen Environments, Dominic George Dieguez

Open Access Theses & Dissertations

Promoted combustion testing is a vital tool for engineers to establish the combustion and flammability characteristics of materials (metallic or otherwise) in oxygen enriched environments. Historically, much of the established data for metallic promoted combustion has been with regards to materials in their cast and wrought forms. However, with the emergence of additive manufacturing as a preferred method of fabrication, the need exists to evaluate how metals in that form behave. Recent testing has demonstrated that even if a metal or alloy is nominally the same with regards to chemistry, flammability between samples in the wrought form can differ significantly …

Earth Abundant Catalyst For Evironmental Sustainability Applications, Javier Hernandez

Open Access Theses & Dissertations

The development of experimental methodologies for synthesizing a diverse range of metallic and metal oxide nanoparticles tailored for sustainable water treatment applications was investigated. These nanoparticles are prepared using environmentally friendly and scalable synthesis methods, underscoring their potential for large-scale production. Synthesized nanoparticles are harnessed for various processes, including catalysis and electrocatalysis, with a primary objective of degrading and removing organic pollutants from water. Key to this research is the encapsulation of nanoparticles within solid supports. Multiple methodologies are explored to engineer supports that ensure nanoparticle stabilization, monodispersion, and prevent unintended release into the environment. Two alternative approaches were evaluated …

Blade Design And Validation Of Hydrokinetic Turbine To Harvest Water Current Energy, Setare Sadeqi

LSU New Orleans Theses and Dissertations

The innovative aspect of this research lies in the careful integration of cutting-edge technologies throughout the entire process of designing, fabricating, and testing the carbon fiber propeller for the 3-bladed horizontal axis ocean current turbine (OCT). SolidWorks software played a pivotal role in the initial design phase, enabling a meticulous and precise modeling of the propeller's geometry. The utilization of SolidWorks allowed for a detailed exploration of various design parameters, ensuring that the propeller's structure and form were optimized for performance in ocean current conditions. Moving beyond the realm of virtual design, the choice of carbon fiber as the fabrication …

Numerical Simulation Of Laser Induced Elastic Waves In Response To Short And Ultrashort Laser Pulses., Alireza Zarei

All Dissertations

In an era of intensified market competition, the demand for cost-effective, high-quality, high-performance, and reliable products continues to rise. Meeting this demand necessitates the mass production of premium products through the integration of cutting-edge technologies and advanced materials while ensuring their integrity and safety. In this context, Nondestructive Testing (NDT) techniques emerge as indispensable tools for guaranteeing the integrity, reliability, and safety of products across diverse industries.

Various NDT techniques, including ultrasonic testing, computed tomography, thermography, and acoustic emissions, have long served as cornerstones for inspecting materials and structures. Among these, ultrasonic testing stands out as the most prevalent method, …

A Methodology For Determining Optimal Milling Parameters For Low-Taper Microtensile Sample Production, Zachary Wayne Barker

Open Access Theses & Dissertations

Femtosecond lasers are beginning to see an increase in interest for industrial and high throughput microsample milling applications. Despite this, much of the literature regarding removal rate studies for ultrashort pulse laser milling continues to focus on single-pulse or similar experiments that have a very small time on target. The material volume removal rates of femtosecond milling can vary wildly depending on parameters like laser scan speed, hatch spacing, z-axis step size, and pulses on the material. Currently, there is no established methodology for determining the optimal values of these parameters for micromilling applications. This methodology was developed in this …

Effect Of The Microstructure On The Corrosion Behavior Of Alcunimn And Alcunimnsi High Entropy Alloys In A 3.5wt% Nacl Solution, Celine Chiong

Open Access Theses & Dissertations

In this study, the AlCuNiMn and AlCuNiMnSi high entropy alloys (HEAs) are investigated to characterize the effect of Si addition and subsequent annealing treatments on the corrosion behavior in a 3.5wt% NaCl solution at room temperature. The microstructure evolution from the as-received condition and after annealing at 600°C, 800°C, and 1000°C for 24 hours in air is examined. The microstructural transformation of HEAs is extensively reported in the literature. However, its impact on the corrosion resistance of HEAs has not received the same attention. In this study, an increase in the annealing temperature of the base AlCuNiMn alloy improved the …

Laser Powder Directed Energy Deposition (Lp-Ded) Inconel 718: Laser Power And Heat Treatment Effect On Microstructure And Mechanical Properties, Dana Victoria Godinez

Open Access Theses & Dissertations

This study examines the microstructure and mechanical properties (tensile, hardness, and fatigue endurance) of laser powder-directed energy deposition (LP-DED) printed specimens with varying deposition parameters. Five samples with power inputs ranging from 350 to 2620W, all of similar thicknesses, were evaluated to enable a direct comparison. The varying specimens were heat treated, including stress relief, hot isostatic pressing, solution, and two-step aging. The resulting microstructures and their corresponding hardness values were compared at each heat treatment stage. The fully heat-treated specimens' tensile properties and fatigue life were also examined and compared. Key findings of this study indicate that complete heat …

Feasibility Study For The Detection Of Damage To Composite Overwrapped Pressure Vessels With Phase Array Ultrasonic Testing, Jordan Scott Hitter

Open Access Theses & Dissertations

When discussing the field of Nondestructive Examination, there are various techniques and instrumentation that can be utilized for analysis of components. However, with newer technology and the development of newer forms of technique, it is critical to explore exactly how these can be applied. This work will aim to explore one newer technique, Phased Array Ultrasonic Testing, and determine the viability of its use for examining Composite Overwrapped Pressure Vessels (COPVs). Currently, the types of vessels have been used in a variety of ways such as in transportation vehicles. More notably, these vessels are used in aerospace applications hence the …

Microstructural Characterization And Oxidation Behavior Of Al-Cu-Ni-Mn And Al-Cu-Ni-Mn-Si Non-Body Centered Cubic High Entropy Alloys, Mckenna Mae Lin Hitter

Open Access Theses & Dissertations

High entropy alloys (HEA) differ from traditional alloying systems because five elements are mixed in equi-atomic proportions, as opposed to having one main principal element. As a result of exploring this new method of alloying, it was found that high entropy alloys demonstrate exceptional mechanical properties, an example being oxidation resistance, and are capable of enduring elevated temperatures. Seeing the potential that this new area of interest contains, studies involving a combination of elements to form various HEA have been performed. Most refractory metals are body-centered cubic and possess extremely high melting temperatures, so they are regularly considered when designing …

Analysis Of Drying Behavior Of Robocasted Barium Titanate, Abigail Ortega

Open Access Theses & Dissertations

Finding an adequate ceramic formulation for material extrusion is a time-consuming process. The necessary equipment may be unavailable to perform the desired test. This study demonstrated an alternative to observe a material after extrusion to understand its drying process. This study focused on 55 solid loading volume percent and a 39 solid loading volume percent, each with two different binder treatments focusing on fresh same day made binder, a 30 day old, aged binder and lastly an artificial binder obtained by a fuming process. Firstly, a formulation was created and loaded onto a pressure-based syringe to be extruded with a …

Improved Ballistic Impact Resistance Of Nanofibrillar Cellulose Films With Discontinuous Fibrous Bouligand Architecture, Colby Caviness

All Theses

Natural protective materials offer unparalleled solutions for impact-resistant material designs that are simultaneously lightweight, strong, and tough. Particularly, the dactyl club of mantis shrimp features chitin nanofibrils organized in a Bouligand structure, which has been shown to effectively dissipate high-impact energy during powerful strikes. The mollusk shells also achieve excellent mechanical strength, toughness, and impact resistance with a staggered, layer-by-layer structure. Previous studies have shown that hybrid designs, by combining different bioinspired microstructures, can lead to enhanced mechanical strength and energy dissipation capabilities. Nevertheless, it remains unknown whether combining Bouligand and staggered structures in nanofibrillar cellulose (NFC) films, forming a …

A Manufacturing-To-Response Pathway For Manufacturing Optimization Of Carbon Fiber Reinforced Polymer Composite Structures, Madhura Limaye

All Dissertations

Over the past decade, there has been an increased adoption of thermoplastic and thermoset based continuous carbon fiber reinforced polymer (CFRP) composites for structural applications in several industries. Among the different manufacturing methods, thermoforming process for thermoplastic based continuous CFRP’s offer a major advantage in reducing cycle times for large scale productions. Similarly, out-of-autoclave curing process for thermoset based continuous CFRP’s using heated tooling enables production of large composite structures. However, these manufacturing processes can have a significant impact on the structural performance of parts by inducing undesirable effects. These effects include inhomogeneous fiber orientations, thickness variations, and residual stresses …

Injectable And Rapidly Expandable Thrombin-Decorated Cryogels Achieve Rapid Hemostasis And High Survival Rates In A Swine Model Of Lethal Junctional Hemorrhage, Syed Muntazir Andrabi, S.M. Shatil Shahriar, Al-Murtadha Al-Gahmi, Benjamin L. Wilczewski, Mark A. Carlson, Jingwei Xie

Department of Mechanical and Materials Engineering: Faculty Publications

Effective therapies are urgently needed to stabilize patients with marginally compressible junctional hemorrhage long enough to get them to the hospital alive. Herein, we report injectable and rapidly expandable cryogels consisting of polyacrylamide and thrombin (AT cryogels) created by cryo-polymerization for the efficient management of lethal junctional hemorrhage in swine. The produced cryogels have small pore sizes and highly interconnected porous architecture with robust mechanical strength. The cryogels exhibit rapid shape memory properties and prove to be resilient against fatigue. These cryogels also show high water/blood absorption capacity, fast blood clotting effect, and enhanced adhesion of red blood cells and …

A Study On High-Frequency Bending Fatigue, Microhardness, Tensile Strength, And Microstructure Of Parts Made Using Atomic Diffusion Additive Manufacturing (Adam) And Additive Friction Stir Deposition (Afsd), Hamed Ghadimi

LSU Doctoral Dissertations

This dissertation reports the findings of several studies on the mechanical and microstructural properties of parts made using atomic diffusion additive manufacturing (ADAM) and additive friction stir deposition (AFSD). The design of a small-sized bending-fatigue test specimen for an ultrasonic fatigue testing system is reported in Chapter 1. The design was optimized based on the finite element analysis and analytical solution. The stress–life (S–N) curve is obtained for Inconel alloy 718. Chapter 2 presents the findings of ultrasonic bending-fatigue and tensile tests carried out on the ADAM test specimens. The S-N curves were created in the very high-cycle fatigue regime. …

Modeling At The Nanometric Scale Of Interfacial Defects Of A Semiconductor Heterostructure In The Isotropic And Anisotropic Cases For The Study Of The Influence Of Stresses, Ahmed Boussaha, Rafik Makhloufi, Rachid Benbouta, Mourad Brioua

Emirates Journal for Engineering Research

This work aims to determine the effect of stresses caused by dislocation networks placed at the interface of a semiconductor heterostructure of the thin GaAs/Si system. In this case, we use a mathematical modeling by Fourier series expansion to numerically simulate the stresses for the two cases of isotropic and anisotropic elasticity in order to predict the mechanical behavior of the heterostructure in the presence of interfacial dislocations while respecting well-defined stress boundary conditions. The elastic stress relaxation is reached for a layer thickness threshold of the GaAs deposit on the Si substrate not exceeding 5 nm.

Copper−Cystine Biohybrid-Embedded Nanofiber Aerogels Show Antibacterial And Angiogenic Properties, Anik Karan, Navatha S. Polavaram, Margarita Darder, Yajuan Su, Syed Muntazir Andrabi, S M Shatil Shahriar, Johnson V. John, Zeyu Luo, Mark A. Decoster, Yu Shrike Zhang, Jingwei Xie

Department of Mechanical and Materials Engineering: Faculty Publications

Copper−cystine-based high aspect ratio structures (CuHARS) possess exceptional physical and chemical properties and exhibit remarkable biodegradability in human physiological conditions. Extensive testing has confirmed the biocompatibility and biodegradability of CuHARS under diverse biological conditions, making them a viable source of essential Cu²⁺. These ions are vital for catalyzing the production of nitric oxide (NO) from the decomposition of Snitrosothiols (RSNOs) found in human blood. The ability of CuHARS to act as a Cu²⁺ donor under specific concentrations has been demonstrated in this study, resulting in the generation of elevated levels of NO. Consequently, this dual function makes …

Implantation Of A Capsular Tension Ring During Cataract Surgery Attenuates Predicted Remodeling Of The Post-Surgical Lens Capsule Along The Visual Axis, Kurt A. Ameku, Caleb C. Berggren, Ryan M. Pedrigi

Department of Mechanical and Materials Engineering: Faculty Publications

Introduction: Cataract surgery permanently alters the mechanical environment of the lens capsule by placing a hole in the anterior portion and implanting an intraocular lens (IOL) that has a very different geometry from the native lens. We hypothesized that implant configuration and mechanical interactions with the post-surgical lens capsule play a key role in determining long-term fibrotic remodeling.

Methods: We developed the first finite element-growth and remodeling (FE-G&R) model of the post-surgical lens capsule to evaluate how implantation of an IOL with and without a capsular tension ring (CTR) impacted evolving lens capsule mechanics and associated fibrosis over …

Engineering Neurotoxin-Functionalized Exosomes For Targeted Delivery To The Peripheral Nervous System, Mena Asha Krishnan, Olawale A. Alimi, Tianshu Pan, Mitchell Kuss, Zeljka Korade, Guoku Hu, Bo Liu, Bin Duan

Department of Mechanical and Materials Engineering: Faculty Publications

The administration of therapeutics to peripheral nerve tissue is challenging due to the complexities of peripheral neuroanatomy and the limitations imposed by the blood–nerve barrier (BNB). Therefore, there is a pressing need to enhance delivery effectiveness and implement targeted delivery methods. Recently, erythrocyte-derived exosomes (Exos) have gained widespread attention as biocompatible vehicles for therapeutics in clinical applications. However, engineering targeted Exos for the peripheral nervous system (PNS) is still challenging. This study aims to develop a targeted Exo delivery system specifically designed for presynaptic terminals of peripheral nerve tissue. The clostridium neurotoxin, tetanus toxin-C fragment (TTC), was tethered to the …

Yap Mechanotransduction Under Cyclic Mechanical Stretch Loading For Mesenchymal Stem Cell Osteogenesis Is Regulated By Rock, Eunju Kim, Brandon D. Riehl, Tasneem Bouzid, Ruiguo Yang, Bin Duan, Henry J. Donahue, Jung Yul Lim

Department of Mechanical and Materials Engineering: Faculty Publications

While yes-associated protein (YAP) is now recognized as a potent mechanosensitive transcriptional regulator to affect cell growth and differentiation including the osteogenic transcription of mesenchymal stem cells (MSCs), most studies have reported the YAP mechanosensing of static mechanophysical cues such as substrate stiffness. We tested MSC response to dynamic loading, i.e., cyclic mechanical stretching, and assessed YAP mechanosensing and resultant MSC osteogenesis. We showed that cyclic stretching at 10% strain and 1 Hz frequency triggered YAP nuclear import in MSCs. YAP phosphorylation at S127 and S397, which is required for YAP cytoplasmic retention, was suppressed by cyclic stretch. We also …