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Articles 1 - 20 of 20
Full-Text Articles in Mechanical Engineering
Dynamics Modeling Of Molten Salt Reactors, Visura Umesh Pathirana
Dynamics Modeling Of Molten Salt Reactors, Visura Umesh Pathirana
Doctoral Dissertations
The abundance of energy is a necessity for the prosperity of humans. The rise in energy demand has created energy shortages and issues related to energy security. Nuclear energy can produce vast amounts of reliable energy without many of the negative externalities associated with other competing energy sources, such as coal and natural gas. As a result, public interest in nuclear power has increased in the past decade. Many new types of nuclear reactor are proposed. These nuclear reactor designs feature many passive technologies that can operate without external influence. Reactors that feature advanced passive safety features are catagorized as …
Stress Relaxation Cracking In 347h Austenitic Steel Weldments Under Various Heat Treatments: Experiments And Modeling, Yi Yang
Doctoral Dissertations
347H austenitic stainless steel exhibits exceptional creep and corrosion resistance, rendering it an exemplary candidate for pipeline materials, particularly in mid- to high-temperature working conditions. However, due to constraints in component dimensions, welding has been chosen as the preferred method for joining pipeline systems extensively employed in nuclear power plants, fossil fuel plants, and petrochemical companies. The welding process entails the accumulation of residual stress during the cooling stage, along with the introduction of microstructure evolution. Moreover, the residual stress field and microstructure continuously evolve under service conditions, thereby intensifying the susceptibility of crack initiation and propagation. The initial residual …
A Two-Diameter Helical Endmill Beam Model For Tool Tip Dynamics Prediction With Application To Milling, Emma D. Betters
A Two-Diameter Helical Endmill Beam Model For Tool Tip Dynamics Prediction With Application To Milling, Emma D. Betters
Doctoral Dissertations
The aim of this dissertation is to describe the dynamic response of helical endmill geometries to enable the use of receptance coupling substructure analysis (RCSA) to predict the tool tip vibration response of arbitrary tool-holder-spindle-machine combinations. The tool tip vibration response, or receptance, is a key input for milling stability prediction. Currently, a measurement is required to determine the tool tip receptance for each tool-holder-spindle-machine combination, which may not be possible in production environments. In the RCSA approach, the spindle receptances are measured once and archived, while the tool and holder are modeled. Tool tip receptances are predicted by analytically …
Additively Manufactured Nature Inspired Morphology For Redesign: Advancing Next Generation Energy Systems, Vanshika Singh
Additively Manufactured Nature Inspired Morphology For Redesign: Advancing Next Generation Energy Systems, Vanshika Singh
Doctoral Dissertations
To meet cleaner energy goals and increasing demand, energy systems such as gas turbines and power plants are required to be operated under harsh loading conditions like higher temperatures and pressures, fluctuating loads, and corrosive environments. Advanced manufacturing techniques such as additive manufacturing (AM) have put us on the trajectory for next-generation system designs, allowing complex geometries and high-temperature alloys with tailored material properties. We need new and systematic design philosophies to use AM's unique characteristics prudently. For a given functionality, nature tends to provide similar solutions in animate and inanimate structures. We propose to take inspiration from nature's repetitive …
Development And Biomechanical Analysis Toward A Mechanically Passive Wearable Shoulder Exoskeleton, Seyyed Morteza Asgari
Development And Biomechanical Analysis Toward A Mechanically Passive Wearable Shoulder Exoskeleton, Seyyed Morteza Asgari
Doctoral Dissertations
Shoulder disability is a prevalent health issue associated with various orthopedic and neurological conditions, like rotator cuff tear and peripheral nerve injury. Many individuals with shoulder disability experience mild to moderate impairment and struggle with elevating the shoulder or holding the arm against gravity. To address this clinical need, I have focused my research on developing wearable passive exoskeletons that provide continuous at-home movement assistance. Through a combination of experiments and computational tools, I aim to optimize the design of these exoskeletons.
In pursuit of this goal, I have designed, fabricated, and preliminarily evaluated a wearable, passive, cam-driven shoulder exoskeleton …
Surface Location Error In Robotic Milling: Modeling And Experiments, Richard Henry Swan Jr.
Surface Location Error In Robotic Milling: Modeling And Experiments, Richard Henry Swan Jr.
Masters Theses
Robotic milling offers new opportunities for discrete part manufacturing as an alternative to milling using large conventional machine tools. The advantage of industrial robots is their large work volume, configurability, and comparatively low cost. However, robots are significantly less stiff than conventional machine tools, which can lead to poor surface finish, low machining accuracy, and low material removal rates. The purpose of this research is to predict the geometric errors, or surface location errors, that occur in a robotic mulling tool path, validate these predictions with machining tests, and compensate these errors by tool path modification. Compared with conventional machine …
Modular Composite Sandwich Structures For Thermal And Structural Retrofitting Of Existing Buildings, Marc Al Ghazal
Modular Composite Sandwich Structures For Thermal And Structural Retrofitting Of Existing Buildings, Marc Al Ghazal
Masters Theses
Around 40% of global energy consumption and 30% of worldwide carbon dioxide (CO2) emissions are attributed to buildings. Most of this consumption is dedicated to ensuring thermal comfort. The goal of this research was to develop and field validate retrofit solutions to improve the energy efficiency of buildings. Exterior cladding panels were designed and tested to ensure adequate thermal and structural performance. Sandwich panels (glass fibers reinforced polymer (GFRP) skins and polymeric foam cores) were fabricated using the vacuum assisted resin transfer molding (VARTM) process. Extruded polystyrene (XPS) and polyurethane (PU) foams were compared as core materials through a series …
Spall Characteristics Of Additively Manufactured Stainless Steel, Kevin Lamb
Spall Characteristics Of Additively Manufactured Stainless Steel, Kevin Lamb
Doctoral Dissertations
Additive manufacturing (AM) has rapidly transformed from a novelty prototyping technology into a growing sector of production across a wide range of industries. Much work has been documented in literature to demonstrate the behavior of AM products under static and quasi-static loading conditions. However, the behavior of AM materials under high strain rate loading is not as well understood. This research attempts to advance the fundamental knowledge of the relationship between the unique aspects of AM and the mechanical performance under high velocity impact loading conditions.
This project examines the behavior of AM 316L stainless steel (SS) exposed to high …
Heat Pump Integrated Thermal Storage For Building Demand Response And Decarbonization, Sara Sultan
Heat Pump Integrated Thermal Storage For Building Demand Response And Decarbonization, Sara Sultan
Doctoral Dissertations
This work presents a novel thermal energy storage (TES) integrated with existing residential heat pump (HP). The research focuses on controls and configuration for energy, demand, cost and carbon emissions savings for residential buildings’ energy consumption. This work will be significant in developing a framework especially for reduced energy demand and carbon emissions associated with space heating and cooling in residential buildings. Since buildings account for about 40% primary energy consumption in U.S. and half of that is associated with HP.
An existing air source HP in integrated with a phase change material (PCM) based TES via active configuration where …
An Automated, Deep Learning Approach To Systematically & Sequentially Derive Three-Dimensional Knee Kinematics Directly From Two-Dimensional Fluoroscopic Video, Viet Dung Nguyen
An Automated, Deep Learning Approach To Systematically & Sequentially Derive Three-Dimensional Knee Kinematics Directly From Two-Dimensional Fluoroscopic Video, Viet Dung Nguyen
Doctoral Dissertations
Total knee arthroplasty (TKA), also known as total knee replacement, is a surgical procedure to replace damaged parts of the knee joint with artificial components. It aims to relieve pain and improve knee function. TKA can improve knee kinematics and reduce pain, but it may also cause altered joint mechanics and complications. Proper patient selection, implant design, and surgical technique are important for successful outcomes. Kinematics analysis plays a vital role in TKA by evaluating knee joint movement and mechanics. It helps assess surgery success, guides implant and technique selection, informs implant design improvements, detects problems early, and improves patient …
Development Of A Soft Robotic Approach For An Intra-Abdominal Wireless Laparoscopic Camera, Hui Liu
Development Of A Soft Robotic Approach For An Intra-Abdominal Wireless Laparoscopic Camera, Hui Liu
Doctoral Dissertations
In Single-Incision Laparoscopic Surgery (SILS), the Magnetic Anchoring and Guidance System (MAGS) arises as a promising technique to provide larger workspaces and field of vision for the laparoscopes, relief space for other instruments, and require fewer incisions. Inspired by MAGS, many concept designs related to fully insertable magnetically driven laparoscopes are developed and tested on the transabdominal operation. However, ignoring the tissue interaction and insertion procedure, most of the designs adopt rigid structures, which not only damage the patients' tissue with excess stress concentration and sliding motion but also require complicated operation for the insertion. Meanwhile, lacking state tracking of …
In Situ Process Monitoring And Machine Learning Based Modeling Of Defects And Anomalies In Wire-Arc Additive Manufacturing, Eduardo Miramontes
In Situ Process Monitoring And Machine Learning Based Modeling Of Defects And Anomalies In Wire-Arc Additive Manufacturing, Eduardo Miramontes
Masters Theses
Wire Arc Additive Manufacturing (WAAM) has made great strides in recent years however, there remain numerous persistent challenges still hindering more widespread adoption. Defects in the parts produced degrade their mechanical performance. Inconsistency in the geometry of the weld beads or undesirable anomalies such as waviness, or humps can lead to loss of geometric accuracy and in extreme cases, when anomalies propagate to subsequent layers, build failure. Such defects can be mitigated by a controls framework, which would require a model that maps undesirable outcomes to information about the process that can be obtained in real time. This thesis explores …
Transient Thermal Performance Enhancement Of Phase Change Materials Through Novel Pin Arrangements Under Varied Gravity Conditions, Junaid Khan
Masters Theses
This thesis presents a comprehensive examination of encapsulation techniques and performance enhancement strategies for Phase Change Materials (PCMs) in the thermal management of spacecraft avionics. This research contributes to optimizing PCM applications in spacecraft through historical analysis, transient thermal performance enhancement, and computational studies.
The first chapter explains the significance of PCMs in passive thermal management since the beginning of space-age technology, it underlines the low thermal conductivity of PCMs and the necessity of incorporating materials with high thermal conductivity, such as metal foams, to improve heat transfer. It also discusses various advancements in PCM research for spacecraft thermal management …
Design Of Machine Tool Cross Beam Using Metal Big Area Additive Manufacturing, Tyler Poon
Design Of Machine Tool Cross Beam Using Metal Big Area Additive Manufacturing, Tyler Poon
Masters Theses
The modern world would not be what it is now without machine tools. Advances in materials and processes, such as carbon fiber and additive manufacturing (AM), enable the design space for machine tool components to expand. However, machine tool components require accurate geometry, which is not available from parts produced by metal Big Area Additive Manufacturing (mBAAM). This project outlines the process in which a traditionally manufactured machine tool component, a welded box structure on an existing machine tool, was redesigned to be made using mBAAM. The goal was to design a structure that was printable using the MedUSA system …
Intelligent Traffic Control With Connected And Automated Vehicles, Yang Shi
Intelligent Traffic Control With Connected And Automated Vehicles, Yang Shi
Doctoral Dissertations
The recent advancements in communication technology, transportation infrastructure, computational techniques, and artificial intelligence are driving a revolution in future transportation systems. Connected and Automated Vehicles (CAVs) are attracting a lot of attention due to their potential to reduce traffic accidents, ease congestion, and improve traffic efficiency. This study focuses on addressing the challenges in controlling future CAV-enabled transportation systems. The aim is to develop a framework for the control of CAV-based traffic systems to improve roadway safety, travel efficiency, and energy efficiency. The study proposes new methods for vehicle speed control and traffic signal control at signalized intersections and corridors …
Investigating The Electrochemical Performance Of Biphenyl-Sodium Polysulfide Organic Redox Flow Batteries, Mohammad Bahzad
Investigating The Electrochemical Performance Of Biphenyl-Sodium Polysulfide Organic Redox Flow Batteries, Mohammad Bahzad
Doctoral Dissertations
With the increased utilization of renewable energy sources, demand for long-duration energy storage systems has increased to moderate the intermittent power generation problem of these sources. Among the various energy storage technologies, those based on electrochemical conversion have received tremendous attention in recent decades. Organic redox flow batteries (ORFBs) are promising candidates for large-scale energy storage. The advantages of ORFBs are flexibility, wide voltage window, high energy density, and low cost. Although recent developments in ORFBs are promising, their future implementation requires further development, especially to understand their electrochemical performance and alleviate system inefficiencies. Most of ORFBs' performance loss comes …
Space-Angle Discontinuous Galerkin Finite Element Method For Radiative Transfer Equation, Hang Wang
Space-Angle Discontinuous Galerkin Finite Element Method For Radiative Transfer Equation, Hang Wang
Doctoral Dissertations
Radiative transfer theory describes the interaction of radiation with scattering and absorbing media. It has applications in neutron transport, atmospheric physics, heat transfer, molecular imaging, and others. In steady state, the radiative transfer equation is an integro-differential equation of five independent variables, which are 3 dimensions in space and 2 dimensions in the angular direction. This high dimensionality and the presence of the integral term present serious challenges when solving the equation numerically. Over the past 50 years, several techniques for solving the radiative transfer equation (RTE) have been introduced. These include, but are certainly not limited to, Monte Carlo …
Correlating Large-Format Additive Manufacturing Processing Parameters To Fiber Length And The Mechanical Performance Of Reinforced Polymer Composites, Andrew Phillip Rhodes
Correlating Large-Format Additive Manufacturing Processing Parameters To Fiber Length And The Mechanical Performance Of Reinforced Polymer Composites, Andrew Phillip Rhodes
Masters Theses
The Big Area Additive Manufacturing (BAAM) system at Oak Ridge National Laboratory has been used to produce carbon fiber reinforced structures for several years, including vehicles, building constituents, composite tooling, etc. While the development of a large-format polymer additive manufacturing (AM) system has moved quickly, the impact of the BAAM’s extruder on the length of carbon fiber feedstock has not been systematically studied. Numerous studies in processing fiber reinforced thermoplastics in plasticizing and injection molding systems have shown that fibers are subjected to significant shear as they are processed, which can cause a drastic reduction in fiber length which negatively …
Enabling Premixed Hydrogen-Air Combustion For Aeroengines Via Laboratory Experiment Modeling, Christopher James Caulfield
Enabling Premixed Hydrogen-Air Combustion For Aeroengines Via Laboratory Experiment Modeling, Christopher James Caulfield
Masters Theses
All combustion systems from large scale power plants to the engines of cars to gas turbines in aircraft are looking for new fuel sources. Recently, clean energy for aviation has come into the foreground as an important issue due to the environment impacts of current combustion methods and fuels used. The aircraft industry is looking towards hydrogen as a new, powerful, and clean fuel of the future. However there are several engineering and scientific challenges to overcome before hydrogen can be deployed into the industry. These issues
range from storing the hydrogen in a viable cryogenic form for an aircraft …
Comparative Analysis On Low Cost Continuous Carbon Fiber Polypropylene Composite Using Compression Molding And Automated Tape Placement, Benjamin U. Schwartz
Comparative Analysis On Low Cost Continuous Carbon Fiber Polypropylene Composite Using Compression Molding And Automated Tape Placement, Benjamin U. Schwartz
Masters Theses
Carbon fiber reinforced plastics (CFRP) are widely used throughout the aerospace industry where a weight reduction remains the highest priority with less emphasis on cost. Textile grade carbon fiber (TCF) and other low cost carbon fiber (LCCF) alternatives have recently emerged for use in the automotive market where emissions regulations have pushed automotive manufacturers and research institutions to look for cost effective light weight materials. Fiber reinforced thermoplastics provide an effective solution that align with automotive design including low cost, high processing rates, high impact toughness, unlimited shelf life, and recyclability.
TCF and Zoltek_PX35 fibers are two LCCF aimed at …