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Articles 1 - 17 of 17
Full-Text Articles in Engineering
Friction Taper Plug Welding As A Repair Method For Fatigue Damage Around Fastener Holes In Aerospace Structures, David Carl Sumsion
Friction Taper Plug Welding As A Repair Method For Fatigue Damage Around Fastener Holes In Aerospace Structures, David Carl Sumsion
Theses and Dissertations
This work details an adaptation of the friction taper plug welding (FTPW) process to repair fatigue damage in 6.35mm AA 7050 t-7451 plate. Aircraft components experience fatigue damage around fastener holes. This damage can be mitigated by enlarging fastener holes. There is no effective repair procedure once holes reach a maximum allowable size. Damaged components must be replaced. A suitable repair process would lead to substantial savings in both time and money. A simulated repair process was developed by machining holes in 6.35mm AA 7050 t-7451 plate. These hoes were then plugged using the FTPW process. Microhardness testing and metallographic …
Enabling Daily Tracking Of Individual’S Cognitive State With Eyewear, Soha Rostaminia
Enabling Daily Tracking Of Individual’S Cognitive State With Eyewear, Soha Rostaminia
Doctoral Dissertations
Research studies show that sleep deprivation causes severe fatigue, impairs attention and decision making, and affects our emotional interpretation of events, which makes it a big threat to public safety, and mental and physical well-being. Hence, it would be most desired if we could continuously measure one’s drowsiness and fatigue level, their emotion while making decisions, and assess their sleep quality in order to provide personalized feedback or actionable behavioral suggestions to modulate sleep pattern and alertness levels with the aim of enhancing performance, well-being, and quality of life. While there have been decades of studies on wearable devices, we …
Investigations Into Flange Surface Friction Effects On Shear Stud Load Transfer In Composite Bridge Girders, Callie Clark
Investigations Into Flange Surface Friction Effects On Shear Stud Load Transfer In Composite Bridge Girders, Callie Clark
Graduate Theses and Dissertations
Composite bridge behavior is commonly achieved through headed shear studs welded tothe steel girder flange and embedded in the concrete deck. Current AASHTO provisions for estimating demands on shear studs during service-level loading consider only bearing load transfer, neglecting adhesion bonding and friction load transfer between the concrete deck and girder flange. Quantifying alternative load transfer mechanisms across the steel-concrete interface may result in improved steel bridge economy by reducing the number of studs required in a composite girder design. This study investigates the effects of flange surface friction (considering various coatings) on resulting stud demands using both experimental testing …
Probabilistic Risk Assessment For Life Extension Of Turbine Engine Rotors, Jace A. Carter, Tarun Goswami
Probabilistic Risk Assessment For Life Extension Of Turbine Engine Rotors, Jace A. Carter, Tarun Goswami
Biomedical, Industrial & Human Factors Engineering Faculty Publications
Maintaining the component service life beyond its historical limits requires the ability to accurately quantify component reliability and address the uncertainties in material responses. A probabilistic method for predicting the total fatigue life was developed and applied to determine the probability of failure of a Ti-6Al-4V turbine disk component. The total fatigue life incorporates a dual mechanism approach including the crack initiation life and propagation life while simultaneously determining the associated initial flaw sizes. A microstructure-based model was employed to address the uncertainties in material response and relate the crack initiation life with crack size. The propagation life was characterized …
Analysis Of The Cyclic Behavior And Fatigue Damage Of Low Alloy Steels, Zahra Salemi Najafabadi
Analysis Of The Cyclic Behavior And Fatigue Damage Of Low Alloy Steels, Zahra Salemi Najafabadi
Dissertations
Fatigue is the most common type of failure in many structures and components subjected to cyclic loading. Surface effects in fatigued materials are of particular importance, since in most cases the surface is the preferred site of fatigue crack initiation. Microcracks originate at the metal surface due to stress concentration introduced by macro notches and micro defects in the surface layers. The microcrack initiation and propagation are controlled by the localized plastic deformation in the surface layers especially in the initial stage of fatigue failure process. Therefore, the knowledge regarding the cyclically induced changes in deformation resistance at the metal …
Assessing Structural And Functional Brain Alterations And Work-Related Fatigue In Non-Hyposmic And Hyposmic Covid-19 Survivors, Rakibul Hafiz
Assessing Structural And Functional Brain Alterations And Work-Related Fatigue In Non-Hyposmic And Hyposmic Covid-19 Survivors, Rakibul Hafiz
Dissertations
In the year 2019, life began to change at the advent of a global pandemic caused by the novel coronavirus. Mask mandates and mass vaccinations have mitigated the effects significantly, yet cases keep rising with new variants, especially, in densely populated countries, like India. Recent neuroimaging evidence shows the virus can attack the central nervous system (CNS). However, exactly which brain regions undergo structural and functional changes remain largely unknown. Many patients experience 'loss of/reduced sense of smell' (i.e., hyposmic) and an alarming number of survivors develop persistent symptoms ('long-COVID') for several months after initial infection. Fatigue is the most …
Cyclic Behavior Of Laterally Skewed Special Moment Frame Connections: Experimental Testing And System-Level Analyses, Mohammad Hossein Kashefizadeh
Cyclic Behavior Of Laterally Skewed Special Moment Frame Connections: Experimental Testing And System-Level Analyses, Mohammad Hossein Kashefizadeh
Graduate Theses and Dissertations
Special moment frames (SMFs) are frequently used in high seismic areas for architecturally constrained designs. SMFs provide lateral system stiffness without the use of braces that often obstruct views and architectural features. Current American Institute of Steel Construction (ASIC) provisions (AISC 341-16) provide prequalified SMF connection details; however, all prequalified details only consider orthogonal connections between the beam and column. This dissertation investigates the effect of adding skew within SMF beam-to-column connections. The study presented herein involves system-level dynamic time-history analyses of skewed SMF connections, the analytical component-level investigation into the effect of the concrete slab on behavior of the …
Analysis Of The Self-Heating Effect On Unfilled Poly(Methyl Methacrylate) Due To Cyclic Behavior, Muhammed R. Kose
Analysis Of The Self-Heating Effect On Unfilled Poly(Methyl Methacrylate) Due To Cyclic Behavior, Muhammed R. Kose
All Theses
Poly(methyl methacrylate, (PMMA) has been implemented as part of the supporting structure in complete hip and knee replacements since the 1950s. Known as bone cement while in the body, PMMA is known to undergo compressive and tensile stresses that wear down the bio-compatible barrier and cause pieces to come loose inside the human body. These pieces are then attacked by the body’s own nervous system, leading to inflammation, and eventually necessitating replacement. It has been documented that under cyclic loading PMMA can reach temperatures that start to degrade its tensile capabilities. In this study the potential cause of self-heating was …
Prediction Of Residual Stresses In L-Pbf Ti-6al-4v Fatigue Specimens Using A Thermo-Mechanical Finite Element Model, Haley Petersen, Brad J. Sampson
Prediction Of Residual Stresses In L-Pbf Ti-6al-4v Fatigue Specimens Using A Thermo-Mechanical Finite Element Model, Haley Petersen, Brad J. Sampson
ME 4233/6233 Fundamentals of FEA
Laser Powder Bed Fusion (L-PBF) is an additive manufacturing process that is becoming widely adopted in the automotive, aerospace, and biomedical industries. It uses a laser to melt metal in the form of powder to build parts in a layer-by-layer fashion based on an imported CAD geometry. The constant remelting of previous layers can produce unwanted thermally induced residual stresses in the part due to large thermal gradients, which can drastically reduce the fatigue life of the material. Predicting these residual stresses within the as-built part would be advantageous because one could better understand how the part will perform in …
On The Influence Of Afp-Induced Defects On Mechanical Behavior Of Composite Laminates Under Fatigue Loading, Pierre Chevalier
On The Influence Of Afp-Induced Defects On Mechanical Behavior Of Composite Laminates Under Fatigue Loading, Pierre Chevalier
Theses and Dissertations
The objective of the work presented in this thesis is to propose and validate a numerical solution to quantify the influence of Automated Fiber Placement (AFP) induced defects on the mechanical behavior of conventional composite laminates in fatigue. The work presented here will be divided in six sections. At first, a description of the Automated Fiber Placement process and its associated defects is proposed. In association, two tools developed for a rapid analysis and a progressive damage analysis respectively are discussed and used as an introduction to the work conducted in this thesis. In the second section, an extensive literature …
Influence Of Cold Expansion And Aggressive Environment On Crack Growth In Aa2024-T3, Ken Shishino, Christopher Leirer, Alberto Mello
Influence Of Cold Expansion And Aggressive Environment On Crack Growth In Aa2024-T3, Ken Shishino, Christopher Leirer, Alberto Mello
Publications
This research aims to establish the effect of hole cold expansion on fatigue life of pre-cracked material under aggressive environment. A relationship between crack propagation and secondary crack initiation was established for AA2024-T3 cold worked holes subjected to cyclic loads to determine the impact on fatigue life of joints in presence of saline solution. Galvanic corrosion of a steel fastener/aluminum plate assembly was investigated assuming the presence of cracks in the aluminum plates, whose growth will be monitored in-situ with a digital microscope throughout the fatigue process. The cold expansion treatment improved the fatigue life fourfold under a corrosive environment, …
Effects Of Lower Limb Cycling Training On Different Components Of Force And Fatigue In Individuals With Parkinson’S Disease, Yen-Po Lin, Rou-Shayn Chen, Vincent Chiun-Fan Chen, Chun-Hsien Liu, Hsiao-Lung Chan, Ya-Ju Chang
Effects Of Lower Limb Cycling Training On Different Components Of Force And Fatigue In Individuals With Parkinson’S Disease, Yen-Po Lin, Rou-Shayn Chen, Vincent Chiun-Fan Chen, Chun-Hsien Liu, Hsiao-Lung Chan, Ya-Ju Chang
Engineering Science Faculty Publications
The strength of lower extremity is important for individuals to maintain balance and ambulation functions. The previous studies showed that individuals with Parkinson’s disease suffered from fatigue and strength loss of central origin. The purpose of this study was to investigate the effect of lower extremities’ cycling training on different components of force and fatigue in individuals with Parkinson’s disease. Twenty-four individuals (13 males, 11 females, mean age: 60.58 ± 8.21 years) diagnosed with idiopathic Parkinson’s disease were randomized into training and control groups. The maximum voluntary contraction (MVC) force, voluntary activation level (VA), and twitch force of knee extensors …
Exploration Of Warm-Up Protocols On Muscular Fatigue, Sahil Kapadia
Exploration Of Warm-Up Protocols On Muscular Fatigue, Sahil Kapadia
Honors Undergraduate Theses
Muscular dystrophy is a genetically linked myopathy with no cure available. The lack of a cure makes early detection and treatment of muscular dystrophy imperative. When reviewing protocols examining muscular fatigue at submaximal isometric contractions, proper warm-up appeared to be absent and could have caused skewed results and conclusions. This study examines the effects of implementing a warm-up protocol before fatiguing trials. In this study, 10 adult subjects conducted fatiguing protocols with the right rectus at submaximal isometric contractions. The warm-up period included a light walk along with contractions at 20% and 33% of maximal voluntary isometric contraction (MVIC) levels. …
Integrating Temperature Dependence Into A Microstructure-Sensitive Fatigue Model For Titanium Alloys, Jared Michael Darius
Integrating Temperature Dependence Into A Microstructure-Sensitive Fatigue Model For Titanium Alloys, Jared Michael Darius
Masters Theses
This work seeks to integrate temperature dependence into a microstructure-sensitive fatigue model for titanium alloys produced by both extrusion and electron beam melting (EBM) additive manufacturing, revising and enhancing the MultiStage Fatigue (MSF) model as the foundational model framework. Traditional fatigue modeling has required design engineers to conservatively use a lower-bound estimate of fatigue life predictions given a statistically significant spread of experimental data that can span up to two or sometimes three orders of magnitude for a given test condition. This variation in fatigue data has since been accounted for with the advent of the MSF model, linking individual …
Investigation Of Pilots' Visual Entropy And Eye Fixations For Simulated Flights Consisted Of Multiple Take-Offs And Landings, Salem M. Naeeri Ph.D., Ziho Kang Ph.D., Ricardo Palma Fraga M.S.
Investigation Of Pilots' Visual Entropy And Eye Fixations For Simulated Flights Consisted Of Multiple Take-Offs And Landings, Salem M. Naeeri Ph.D., Ziho Kang Ph.D., Ricardo Palma Fraga M.S.
Journal of Aviation/Aerospace Education & Research
Eye movement characteristics might provide insights on pilots' mental fatigue during prolonged flight. The visual entropy, eye fixation numbers, and eye fixation durations of ten novice pilots and ten expert pilots were analyzed for a four-hour simulated flight task consisting of four consecutive flight legs. Each flight leg lasted approximately one hour and contained five flight phases: takeoff, climb, cruise, descend, and landing. The pilots maneuvered the simulated B-52 aircraft following instrument flight rules (IFR) in a moderate-fidelity Microsoft Flight Simulator environment. Our results indicate that experts’ eye movement characteristics were significantly different from those of novices. In detail, novices' …
Fatigue In Aircraft Maintenance Technician Schools, Natalie Zimmermann, Peng Hao Wang, Keegan Pullen
Fatigue In Aircraft Maintenance Technician Schools, Natalie Zimmermann, Peng Hao Wang, Keegan Pullen
International Journal of Aviation, Aeronautics, and Aerospace
Fatigue has long been identified as a human factor in aviation. Subsequently, a series of studies have highlighted fatigue-related elements within the context of the aviation industry, focusing on the flight deck – with some extension to flight students – and aviation maintenance activities. However, the latter has not been as deeply examined as its flight crew-centered counterpart. Similarly – if not more significantly – fatigue experienced by aircraft maintenance technician (AMT) students is scarcely explored, especially in comparison to the research conducted to understand fatigue in flight schools. AMT students are subject to comparable, but not the same, experiences …
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
Vibration Bending Fatigue Analysis Of Additively Repaired Ti-6al-4v Airfoil Blades, Lucas Jordan Smith
Browse all Theses and Dissertations
Repairing airfoil blades is necessary to extend the life of turbine engines. Directed energy deposition (DED) additive manufacturing (AM) provides the ability to add material at a specific location on an existing component. In this work, AM repairs on Ti-6Al-4V airfoil blades were analyzed to determine what effect the repair will have on the blade performance in high cycle vibration fatigue testing. Targeted sections were cut out of airfoil blades near high stress locations and repaired using DED. To understand the defects that arose with this type of repair, computed tomography imaging was used to quantify the defects from the …