Mechanical Engineering Commons^™

Dynamic Modeling And Extreme Tension Analysis Of Mooring System For A Floating Offshore Wind Turbine, Wei Ting Hsu

Electronic Theses and Dissertations

For offshore wind industry, exploiting the dynamic behaviors of mooring lines is of increasing importance in floating offshore wind turbine (FOWT) mooring system design. Currently, the design philosophy for structures and moorings is based on principles and practices adopted in offshore oil and gas, including mooring systems that are optimized for applications in deeper waters. However, the design of FOWT mooring systems is facing several challenges, including installation costs, the stability of light-weight minimalistic platforms, and shallow water depths (50-300m). The extreme tension in mooring lines of a light displacement platform in shallow water is dominated by snap loads. Hence …

Modeling Of A Head - Neck Assembly Drop Tower Impact Test Using Abaqus, Hussein Sharqi Owaid

Electronic Theses and Dissertations

There are numerous potential causes of traumatic brain injury (TBI) and concussions, including traffic accidents, contact during sports and falls. Protection from these injuries is paramount because of the problems that result from TBI, such as loss of thinking and memory capability. Head impact from falls, especially in elderly, can also result in severe to fatal injury and some effects of brain injury are often not visible. For these reasons and more a need exists for protective head gear that can keep persons safe during at risk physical activity and that can protect fall prone persons from accidental injuries. Part …

Habitat Use Of Blacktip Sharks (Carcharhinus Limbatus) At Fishing Piers, Kelsey L. Spencer

Electronic Theses and Dissertations

Blacktip sharks (Carcharhinus limbatus) can be observed near fishing piers throughout the summer along the northeast coast of South Carolina. These piers attract and support a wide variety of potential prey and sharks are able to forage on fishers’ discards with minimal energetic cost. I tagged 12 blacktip sharks with acoustic transmitters, monitored piers with acoustic receivers, and conducted pier-creel surveys to determine the habitat use of blacktip sharks at fishing piers, factors that influenced residence time and presence/absence at piers, and any cyclical patterns in visits to piers. Data were analyzed with pier association indices (PAI), mixed models, and …

Material Properties Design Using Simulations And Experiments For Powder Injection Molding Of Lead Zirconate Titanate (Pzt)., Bhushan Pramod Bandiwadekar

Electronic Theses and Dissertations

Powder injection molding (PIM) process simulations can be performed to minimize the number of injection molding experiments by estimating material properties necessary for PIM simulations. In current work, lead zirconate titanate (PZT) powder-polymer binder feedstock was compounded for 45 vol. % and 52 vol. % solids loading. PIM experiments on designed micro-pillar array geometry were performed using 52 vol. % PZT. Using PIM experiments results as basis, PIM simulations were performed on designed micro-pillar array geometries to understand the effectiveness of PIM simulations with the use of estimated feedstock properties in predicting molding behavior that have micro-features. Additionally, PIM simulations …

Fused Filament Fabrication 3d Printing Using Low-Melting Alloys., Nirupama Warrier

Electronic Theses and Dissertations

Fused Filament Fabrication (FFF) 3D printing technology has been a popular method of creating prototypes using plastics in the timeliest and most affordable manner for electronic, automotive, and biomedical applications. 3D printing of metals and alloys using FFF technology could provide low-cost alternatives and solutions to the Laser-Powder Bed Fusion Process (L-PBF) and Binder Jetting processes (BJ). In current work, low melting alloys have been used as a starting material and evaluated for FFF 3D printing using two methodologies. In the first methodology, Sn60Bi40 alloy in the form of wire was used as the feedstock for FFF extrusion and process …

Design, Analysis, And Application Of A Cellular Material/Structure Model For Metal Based Additive Manufacturing Process., Shanshan Zhang

Electronic Theses and Dissertations

Powder bed fusion additive manufacturing (PBF-AM) has been broadly utilized to fabricate lightweight cellular structures, which have promising potentials in many engineering applications such as biomedical prosthesis, aerospace, and architectural structures due to their high performance-to-weight ratios and unique property tailorabilities. To date, there is still a lack of adequate understanding of how the cellular materials are influenced by both the geometry designs and process parameters, which significantly hinders the effective design of cellular structures fabricated by PBF-AM for critical applications. This study aims to demonstrate a cellular structure design methodology that integrates geometrical design and process-material property designs. Utilizing …

Transformation Of Nonlinear Waves In The Presence Of Wind, Current, And Vegetation, Haifei Chen

Electronic Theses and Dissertations

Accurate prediction of extreme wave events is crucial for the safe maritime activities and offshore operations. Improved knowledge of wave dissipation mechanisms due to breaking and vegetation leads to accurate wave forecast, protecting life and property along the coast. The scope of the thesis is to examine the wave transformations in the presence of wind, current, and vegetation, using a two-phase flow solver based on the open-source platform OpenFOAM. The Reynolds-Averaged Navier-Stokes (RANS) equations are coupled with a Volume of Fluid (VOF) surface capturing scheme and a turbulence closure model. This RANS-VOF model is adapted to develop a numerical wind-wave-current …

The Application Of Proper Orthogonal Decomposition To Numerically Modeled And Measured Ocean Surface Wave Fields Remotely Sensed By Radar, Andrew Joseph Kammerer

Electronic Theses and Dissertations

Phase-resolved ocean surface wave elevation maps provide important information for many scientific research areas (e.g., rogue waves, wave-current interactions, and wave evolution/growth) as well as for commercial and defense applications (e.g., naval and shipping operations). To produce these maps, measurements in both time and space are necessary. While conventional wave sensing techniques are limited spatially, marine radar has proven to be a complex yet promising remote sensing tool capable of providing both temporal and spatial wave measurements. The radar return from the sea surface is complex because it contains contributions from many sources only part of which provide information about …

Piezoelectric Bistable Buckled Beam Energy Harvester., Brian Edward Allgeier

Electronic Theses and Dissertations

A novel energy harvesting device design is presented to be created via microfabrication techniques. Such devices have countless applications for powering low-current electrical devices, especially wireless sensors or transmitters. This micro-electromechanical system (MEMS) design utilizes the piezoelectric response of a bistable buckled beam to gather electrical energy via ambient vibrations. While many traditional piezoelectric energy harvesters (PEH) consist of simple cantilever beam geometries, this nonlinear design utilizes inertial effects of torsional lever arms to actuate a central buckled beam to snap between its two stable states; such an abrupt strain on the piezoelectric beam potentially produces a significantly increased electrical …

Biomechanical Testing Of An Exercise For Strengthening The Proximal Femur., Alyssa Osbourne

Electronic Theses and Dissertations

Based on the principles of cutting edge bone remodeling research, a unique therapeutic exercise device was designed specifically to improve bone quality at the most critical location of the proximal femur prone to fracture: the superior-lateral femoral neck where the fracture first initiates during a fall. The exercise/device is intended to work by inducing enough strain in the bone to stimulate the body’s natural bone remodeling mechanisms to increase bone density in the proximal femur and consequently prevent a fracture from arising if a fall to the side does occur.

In order to test the proposed exercise, experiments simulating the …

Investigation Of Lattice Structures And Analysis Of Strut Geometry., Zachary D Denzik

Electronic Theses and Dissertations

This study involves the evaluation of lattice specimens fabricated using additive manufacturing as well as investigation of the influence of unit cell connection geometry. Lattice topologies of face-centered cells and body-centered cells were modeled, investigated using finite element analysis (FEA) for each specimen, manufactured using direct metal laser sintering (DMLS) with maraging steel powder, and mechanically tested. The strut diameter of each topology was altered to yield four different mass reductions from a solid cube, ranging from 55%-90% mass reduction. Three iterations of 1000mm³ lattice specimens were investigated. The first iteration consisted 0.5mm plates on the top and bottom …

Feasibility Of Using 3d Printed Molds For Thermoforming Thermoplastic Composites, Sunil Bhandari

Electronic Theses and Dissertations

This thesis presents a novel combined experimental and numerical mechanics approach for characterizing 3D printed thermoplastic materials by the fused deposition modeling process for thermoforming thermoplastic composites. The implications of this work are:

1. a methodology for model-based performance evaluation of 3D printed structural parts, and
2. an improved design of 3D printed molds for composites manufacturing, which has potential for material innovations and scaled-up applications in additive manufacturing.

The thesis formulates basic criteria for selection of thermoplastic polymer used for the 3D printed mold based on forming temperatures. The thesis creates a lattice and shell finite element model of the 3D …

The Development Of A Vacuum Forming System For Kydex® And Other Thermoplastic Sheet, Andrew G. Smith

Electronic Theses and Dissertations

Vacuum forming is a popular, cost effective method amongst large and small scale applications. The method is used to mold a material to the surface of a mold/pattern in order to create a negative copy for reproduction or an object in positive form. The prototype vacuum forming system developed and documented herein is of a membrane-seal type that consists of three (3) principle parts: radial platen, Hinged Frame and Platen Support Assembly, and a PVC surge tank. Each part is described in detail through design, manufacturing, and testing processes. The design supports functional versatility, small scale molding, and uses readily …

Development And Evaluation Of A Biocompatible Electroactive Sensor For Continuous Blood Pressure Measurement., Scott D. Cambron

Electronic Theses and Dissertations

Piezo-active composites have been implemented for sensing and transduction for decades. The 0-3 ceramic/polymer composite is one of the most common composite types used for sensing applications, owing to their tailorable properties of the two-phase composition, consisting of a three-dimensionally connected polymer/rubber matrix (inactive phase) with a dispersion of isolated piezo-ceramic particles (active phase). This thesis describes a method to develop novel biocompatible perivascular band comprised of a two-phase piezo-active composite to be fabricated using simple manufacturing processes. Biomaterials such as tissue scaffolds comprised of silk fibroin (SF) and chitosan (CS), and biocompatible soft rubbers will be implemented as the …

Continuous Oscillation: Vibrational Effects And Acceptable Frequency Ranges Of Small Bore Piping In Field Applications, Marie Kasprzyk

Electronic Theses and Dissertations

In turbomachinery, a common failure mode is cracking of welds at the equipment and piping connection point. Each incidence of these cracks causes a forced shutdown to perform repairs that cost millions of dollars. This type of failure is predominately seen in small bore piping, which has a nominal diameter of 2 inches and smaller. This thesis addresses the failure prediction analysis of small bore piping, specifically in turbomachinery applications. Performing failure analysis to predict the potential cracking of welds will allow for replacement of the piping during a planned shutdown which in the long term saves money due to …

Tensile-Compressive Asymmetry And Anisotropy Of Fused Deposition Modeling Pla Under Monotonic Conditions, Casey Perkowski

Electronic Theses and Dissertations

Additive Manufacturing (AM) continues to gain popularity for its ability to produce complexly-shaped final use components that are impractical to manufacture by traditional methods; however, additive manufactured parts contain complex mesostructures that result in directionally-dependent mechanical properties that have yet to be fully characterized. This effort demonstrates a framework of experimental and analytical methods needed to characterize the uniaxial monotonic behavior of fused deposition modeling PLA using tensile and compressive experiments on specimens printed at various orientations. Based on experimental results, the asymmetry and anisotropy of the tensile and compressive response was analyzed for a candidate material. Specimens from different …

A Study On The Plasticity And Fracture Behaviors Of Inconel 718 Under Multiaxial Stress And Extremely Low Cycle Fatigue Loadings, Mohammed Algarni

Electronic Theses and Dissertations

Engineering materials and structures are usually subjected to multiaxial stress states loading due to geometrical effects, residual stresses, or multi-directional loading. Ductile fracture and Extremely Low Cycle Fatigue (ELCF), less than 100 cycles to fail, are two common and co-exist failure modes in many engineering structures. However, the linkage between these two failure modes under multi-axial loading conditions has never been systematically studied. This research summarizes an extensive work of experimental and numerical studies of ductile fracture and ELCF under different stress states for nickel-base superalloy material "IN718" under room temperature. Specially designed specimens and tests were used to achieve …

Academic Blade Geometries For Baseline Comparisons Of Forced Vibration Response Predictions, James Little

Electronic Theses and Dissertations

Predicting the damping associated with underplatform dampers remains a challenge in turbomachinery blade and friction damper design. Turbomachinery blade forced response analysis methods usually rely on nonlinear codes and reduced order models to predict vibration characteristics of blades. Two academic blade geometries coupled with underplatform dampers are presented here for comparison of these model reduction and forced response simulation techniques. The two blades are representative of free-standing turbine blades and exhibit qualitatively similar behavior as highly-complex industrial blades. This thesis fully describes the proposed academic blade geometries and models; it further analyzes and predicts the blades forced response characteristics using …

Computational Fluid Dynamics Study Of Thromboembolism As A Function Of Shunt Size And Placement In The Hybrid Norwood Palliative Treatment Of Hypoplastic Left Heart Syndrome, John Seligson

Electronic Theses and Dissertations

The Hybrid Norwood procedure has emerged as a promising alternative palliative first stage treatment for infants with Hypoplastic Left Heart Syndrome (HLHS). The procedure is done to provide necessary blood flow to the pulmonary and systemic regions of the body. The procedure can affect hemodynamic conditions to be pro-thrombotic, and thrombus particles can form and release from the vessel walls and enter the flow. Assuming these particles are formed and released from the shunt surface, a Computational Fluid Dynamics (CFD) model can be used to mimic the patient's vasculature geometry and predict the occurrence of embolization to the carotid or …

Investigation Of Heat Transfer Enhancement Within A Concentric Annulus, Alexander Hanhold

Electronic Theses and Dissertations

Effective heat exchange is key for many energy applications including heat exchangers, heat extraction from heat source, and heat rejection to ambient thermal sink. This study focuses on the investigation for a specific heat exchange configuration, namely heat removal within a concentric annular passage using helical turbulators and jet impingement. Numerical testing was used to see how the different geometric parameters affect the heat transfer and pressure drop within the annulus by using helicoil turbulators. A vast range of designs were studied by changing the turbulator shape, pitch, and blockage ratio while maintaining a constant Reynolds number of 25,000. CFD …

Chaotification As A Means Of Broadband Vibration Energy Harvesting With Piezoelectric Materials, Daniel Geiyer

Electronic Theses and Dissertations

Computing advances and component miniaturization in circuits coupled with stagnating battery technology have fueled growth in the development of high efficiency energy harvesters. Vibration-to-electricity energy harvesting techniques have been investigated extensively for use in sensors embedded in structures or in hard-to-reach locations like turbomachinery, surgical implants, and GPS animal trackers. Piezoelectric materials are commonly used in harvesters as they possess the ability to convert strain energy directly into electrical energy and can work concurrently as actuators for damping applications. The prototypical harvesting system places two piezoelectric patches on both sides of the location of maximum strain on a cantilever beam. …

Ellipsometric Measurements Of Alternative Fuels, Leigh Nash

Electronic Theses and Dissertations

Alternative jet fuels will be important in the future to ensure cleaner burning, reliable, and reasonably priced air transportation. One important property that must meet certification standards is the fuel's thermal stability, or its ability to withstand heating before breaking down. Jet fuels are used as engine coolants, and thermally unstable fuels can form deposits in the fuel delivery systems, leading to a loss of fuel flow. In the past, the thermal stability of a fuel was rated using a color standard method. The color of the deposit left on a metal tube that had been heated and exposed to …

Multi-Axial Thermomechanical Characterization Of Shape Memory Alloys For Improved Stability, Douglas Nicholson

Electronic Theses and Dissertations

Shape recovery in shape memory alloys (SMAs) occurs against external stress by means of a reversible thermoelastic solid state phase transformation typically between so-called austenite, martensite and R-phases. The ability to do work enables their use as high-force actuators in automotive and aerospace applications while superelastic NiTi is of interest in biomedical devices such as stents. Both R-phase and martensite can detwin, reorient and undergo a thermal or stress induced transformation. For these reasons, it is difficult from ordinary macroscopic measurements to decouple elastic and inelastic contributions (from their respective phases) from the overall deformation. In situ neutron diffraction is …

Local Transient Characterization Of Thermofluid Heat Transfer Coefficient At Solid-Liquid Nano-Interfaces, Mehrdad Mehrvand

Electronic Theses and Dissertations

The demands for increasingly smaller, more capable, and higher power density technologies in microelectronics, energy, or aerospace systems have heightened the need for new methods to manage and characterize extreme heat fluxes (EHF). Microscale liquid cooling techniques are viewed as a promising solution for removing heat from high heat flux (HHF) systems. However, there have been challenges in physical understanding and predicting local thermal transport at the interface of micro and nanoscale structures/devices due to ballistic effects and complex coupling of mass, momentum, and energy transport at the solid-liquid-vapor interfaces over multiple time and length scales. Moreover, it's challenging to …

Computational Fluid Dynamics Proof Of Concept And Analysis Of A Self-Powered Fontan Circulation, Marcus Ni

Electronic Theses and Dissertations

The Fontan circulation is a result of the last (third stage) surgical procedure to correct a single ventricle congenital cardiac disorder in children. Although the Fontan circulation has been successfully established in surgeries over the years, it is flawed and can lead in certain cases to pre-mature death. The main cause of this failure is due to increased pulmonary vascular resistance due to loss pulse pressure and blood flow. In healthy circulations, the heart pumps directly to the lungs, where as "Single Ventricle" patients must use a single sided heart to supply blood to the rest of the body before …

Assessing The Near-Wall Hemodynamics In The Left Coronary Artery Using Cfd, John Junior Asiruwa

Electronic Theses and Dissertations

The objective of this thesis is to computationally investigate the flow mechanics and the near-wall hemodynamics associated with the different take-off angles in the left coronary artery of the human heart. From this study, we will be able to evaluate if the increase in the take-off angles of the left coronary artery will significantly increases or decrease the likelihood of plaque (atherosclerosis) buildup in the left coronary artery bifurcations. This study quantifies the effects of the varying take-off angles on the branches along the left anterior descending (LAD) of the left coronary artery using computational fluid dynamics (CFD) simulations. The …

Assessment Of Varying Model Representations In Cfd Simulations, Caitlin R. Gerdes

Electronic Theses and Dissertations

This thesis investigates the effects of varying model refinement and representation of computational fluid dynamics (CFD) simulations in two case studies. Product and process realization in engineering design requires substantial resources (time and money) in order to test novel designs for effectiveness. In recent decades, engineering has been relying more heavily on simulation-based analysis in the design process with computer models to help reduce the demands for real-life testing. The first case study analyzed in this thesis is a photobioreactor, which is used to grow microalgae for biofuel and require a balance of nutrients, light, and mixing for growth. The …

Development Of Heterogeneous Catalysts For Upgrading Biomass Pyrolysis Bio-Oils Into Advanced Biofuels, Shouyun Cheng

Electronic Theses and Dissertations

The massive consumption of fossil fuels and associated environmental issues result in an increased interest in alternative resources such as biofuels. The renewable biofuels can be upgraded from bio-oils that are derived from biomass pyrolysis. Catalytic cracking and hydrodeoxygenation (HDO) are two most promising bio-oil upgrading techniques for biofuel production. Heterogeneous catalysts are essential for upgrading bio-oil into hydrocarbon biofuel. Although some progresses have been made, the cost and effectiveness of catalysts still remain challenges. The main objective of this study was to develop efficient heterogeneous catalysts for upgrading bio-oils into advanced hydrocarbon biofuel with low costs. In catalytic cracking, …

Simulations Of Impinging Jet With A Range Of Configuration, Devansh Singh

Electronic Theses and Dissertations

Impinging jet technique is widely increasing across the globe due to its ability to produce high heat and mass transfer as compared to other traditional methods. Three cases of impinging jets related to cooling technologies for a gas turbine were investigated. The first case involves a single jet impinging on a flat plate. The second case has an array of jets impinging on a curved surface. The third case deals with simulating impinging jet in crossflow. The first case was used for validation and shows the effect of mesh and inlet boundary conditions. After careful observation, it was seen that …

Cfd Analysis Methods For Systems Driven By Natural Convection, Aaron Propst

Electronic Theses and Dissertations

Natural convection driven flows are present in many engineering applications such as HVAC, electronics cooling, and cryogenic systems. Predicting the flow behavior of such systems requires experimentation or numerical simulation through Computational Fluid Dynamics due to the complex interactions of natural convection. Recent advances in computing resources have made CFD increasingly popular for engineering analysis of fluid dynamics and heat transfer. CFD simulation has several advantages over experimentation including: 1) cost, 2) ease of changing design parameters, and 3) time required to obtain results. These advantages lead to an increased likelihood of discovering an optimal design. However, systems with complex …