Modeling Residual Stress Development In Hybrid Processing By Additive Manufacturing And Laser Shock Peening, 2018 University of Nebraska - Lincoln
Modeling Residual Stress Development In Hybrid Processing By Additive Manufacturing And Laser Shock Peening, Guru Charan Reddy Madireddy
Mechanical (and Materials) Engineering -- Dissertations, Theses, and Student Research
The term “hybrid” has been widely applied to many areas of manufacturing. Naturally, that term has found a home in additive manufacturing as well. Hybrid additive manufacturing or hybrid-AM has been used to describe multi-material printing, combined machines (e.g., deposition printing and milling machine center), and combined processes (e.g., printing and interlayer laser re-melting). The capabilities afforded by hybrid-AM are rewriting the design rules for materials and adding a new dimension in the design for additive manufacturing paradigm. This work focuses on hybrid-AM processes, which are defined as the use of additive manufacturing (AM) with one or more ...
Evaluation Of High Velocity Wear, 2018 Air Force Institute of Technology
Evaluation Of High Velocity Wear, Armando Deleon
Theses and Dissertations
The HHSTT located at Holloman Air Force Base conducts hypersonic testing in a unique way. Rather than perform cost prohibitive flight testing or hypersonic wind tunnel testing, a rocket-powered sled propels test articles down a track. This test setup has been used to test at speeds up to 2885 m/s (~Mach 8.6). The sled is kept on the rails by utilizing slippers, fabricated to wrap around the rail . This slipper design keeps the sled from separating from the rail during a test due to the airflow producing lift, in a designed effort to minimize the wear that ...
Powder Bed Surface Quality And Particle Size Distribution For Metal Additive Manufacturing And Comparison With Discrete Element Model, 2018 California Polytechnic State University, San Luis Obispo
Powder Bed Surface Quality And Particle Size Distribution For Metal Additive Manufacturing And Comparison With Discrete Element Model, Irene Yee
Master's Theses and Project Reports
Metal additive manufacturing (AM) can produce complex parts that were once considered impossible or too costly to fabricate using conventional machining techniques, making AM machines an exceptional tool for rapid prototyping, one-off parts, and labor-intensive geometries. Due to the growing popularity of this technology, especially in the defense and medical industries, more researchers are looking into the physics and mechanics behind the AM process. Many factors and parameters contribute to the overall quality of a part, one of them being the powder bed itself. So far, little investigation has been dedicated to the behavior of the powder in the powder ...
Erosion Degradation Characteristics Of A Linear Electro-Hydrostatic Actuator Under A High-Frequency Turbulent Flow Field, 2018 Old Dominion University
Erosion Degradation Characteristics Of A Linear Electro-Hydrostatic Actuator Under A High-Frequency Turbulent Flow Field, Yuan Li, Shaoping Wang, Mileta M. Tomovic, Chao Zhang
Engineering Technology Faculty Publications
The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization ...
Mechanical Wear Debris Feature, Detection, And Diagnosis: A Review, 2018 Old Dominion University
Mechanical Wear Debris Feature, Detection, And Diagnosis: A Review, Wei Hong, Wenjian Cai, Shaoping Wang, Mileta M. Tomovic
Engineering Technology Faculty Publications
Mechanical debris is an important product of friction wear, which is also a crucial approach to know the running status of a machine. Many studies have been conducted on mechanical debris in related fields such as tribology, instrument, and diagnosis. This paper presents a comprehensive review of these studies, which summarizes wear mechanisms (e.g., abrasive wear, fatigue wear, and adhesive wear) and debris features (e.g., concentration (number), size, morphology, and composition), analyzes detection methods principles (e.g., offline: spectrograph and ferrograph, and online: optical method, inductive method, resistive-capacitive method, and acoustic method), reviews developments of online inductive methods ...
Characterization Of A Novel Variable Friction Connection For Semi-Active Cladding System, 2018 Iowa State University
Characterization Of A Novel Variable Friction Connection For Semi-Active Cladding System, Yongqiang Gong, Liang Cao, Simon Laflamme, Spencer Quiel, James Ricles, Douglas Taylor
Civil, Construction and Environmental Engineering Publications
Cladding systems are conventionally designed to serve architectural purposes and protect occupants from the environment. Some research has been conducted in altering the cladding system in order to provide additional protection against natural and man-made hazards. The vast majority of these solutions are passive energy dissipators, applicable to the mitigation of single types of hazards. In this paper, we propose a novel semiactive variable friction device that could act as a connector linking a cladding panel to the structural system. Because of its semi-active capabilities, the device, here termed variable friction cladding connection (VFCC), could be utilized to mitigate different ...
Application Of Surface Treatments To Improve Fuel Efficiency Of Internal Combustion Engines, 2017 Louisiana State University and Agricultural and Mechanical College
Application Of Surface Treatments To Improve Fuel Efficiency Of Internal Combustion Engines, Amirabbas Akbarzadeh
LSU Master's Theses
To improve the tribological performance of contacting surfaces, different surface modification methods can be employed. Surface texturing and surface coating are examples of viable techniques developed for this purpose. Surface texturing involves creating micropatterns on the contacting surfaces while surface coating requires depositing a thin layer of a suitable material on the surface(s) to improve the component’s friction and wear characteristics. The performance of textured surfaces is affected by the geometric characteristic of textures.When dealing with surface coating parameters, the parameters of interests are the type of coating materials and their thicknesses.
The current study aims to ...
Silicon Carbide Materials Properties Selection For Mechanical Seal Faces, 2017 University of Tennessee, Knoxville
Silicon Carbide Materials Properties Selection For Mechanical Seal Faces, William Charles Hoskins
University of Tennessee Honors Thesis Projects
No abstract provided.
Modeling And Computation Of The Maximum Braking Energy Speed For Transport Category Airplanes, 2017 AAR Aerospace Consulting, LLC
Modeling And Computation Of The Maximum Braking Energy Speed For Transport Category Airplanes, Nihad E. Daidzic
Journal of Aviation Technology and Engineering
Transport-category or FAR/CS 25 certified airplanes may occasionally become braking energy capacity limited. Such limitation may exist when heavy airplanes are departing airports at high-density altitudes, on relatively long runways, and/or possibly with some tailwind component. A maximum braking energy VMBE speed exists which may limit the maximum allowable takeoff decision/action speed V1. The ever-existing possibility of high-speed rejected takeoff in such conditions may also limit the airplane gross weight for declared available distances. To gain deeper insights and acquire better understanding of the topic, a theoretical model of the maximum braking energy and the related VMBE ...
Investigation Of An Axial Flow Rotary Valve Seal, 2017 University of Kentucky
Investigation Of An Axial Flow Rotary Valve Seal, Joseph K. Stieha
Theses and Dissertations--Mechanical Engineering
This thesis investigates potential materials to be used in the rotary sealing industry that provide low power loss and minimize cost. The studied rotary valve utilizes slots that act as timing valves to allow for flow axially, through the seal face, at particular times within a heat pump cycle. This investigation examines various combinations of multiple PTFE materials, plastics, and soft metals that have been proven to provide low friction coefficients. Leakage and wear requirements are stated for the future use of the rotary valve and are used to determine the effectiveness of sealing the fluid while examining the power ...
Tribological Testing And Analysis Of Ionic Liquids As Candidate Anti-Wear Additives For Next-Generation Engine Lubricants, 2016 University of Tennessee - Knoxville
Tribological Testing And Analysis Of Ionic Liquids As Candidate Anti-Wear Additives For Next-Generation Engine Lubricants, William Charles Barnhill
In this work, fourteen ionic liquids (ILs) were assayed as potential next-generation engine oil additives. After screening for corrosion, thermal stability and oil solubility, candidate additives were subjected to friction and wear tests in both boundary and mixed regime lubrication. While each IL demonstrated friction and wear reduction compared to base oil without any additives, oil miscible ILs tetraoctylphosphonium bis 2-ethylhexyl phosphate ([P8888][DEHP]) and trioctylammonium bis 2-ethylhexylphosphate ([N888H][DEHP]) were the best performers in bench tests with a XX% and XX% improvement in wear over the base oil respectively. Each of these ILs excellent solubility and superior performance was ...
Study Of Role Of Meniscus And Viscous Forces During Liquid-Mediated Contacts Separation, 2016 Minnesota State University Mankato
Study Of Role Of Meniscus And Viscous Forces During Liquid-Mediated Contacts Separation, Prabin Dhital
All Theses, Dissertations, and Other Capstone Projects
Menisci may form between two solid surfaces with the presence of an ultra-thin liquid film. When the separation operation is needed, meniscus and viscous forces contribute to an adhesion leading stiction, high friction, possibly high wear and potential failure of the contact systems, for instance microdevices, magnetic head disks and diesel fuel injectors. The situation may become more pronounced when the contacting surfaces are ultra-smooth and the normal load is small. Various design parameters, such as contact angle, initial separation height, surface tension and liquid viscosity, have been investigated during liquid-mediated contact separation. However, how the involved forces will change ...
Investigation Of Friction Mechanisms In Finger Pad Sliding Against Surfaces Of Varying Roughness, 2015 Iowa State University
Investigation Of Friction Mechanisms In Finger Pad Sliding Against Surfaces Of Varying Roughness, Geetha Chimata, Christian J. Schwartz
Mechanical Engineering Publications
Human finger pad friction and the effects of surface features on the fingerprint ridges, shape of the finger and the material properties of the finger were investigated. The friction coefficients for three fine-grit abrasive papers were measured to assess these effects. Four probing surfaces were used: human index finger pad, silicone replicas of the finger with and without fingerprints, and a smooth silicone sphere. Friction tests were performed at a constant normal load of 0.5 N in two probe orientations: normal and perpendicular to the orientation of the fingerprint ridges. Scanning electron microscopy of the abrasive papers was performed ...
Application Of Ultrasound In The Measurement Of Lubricant Fluid Film Thickness In The Piston-Cylinder Interface Of An Axial Piston Pump, Dhruv Subramaniam, Dan Mizell, Monika Ivantysynova
The Summer Undergraduate Research Fellowship (SURF) Symposium
In this paper a feasibility study has been conducted to determine a technique for the measurement of lubricant fluid film thickness in the piston-cylinder interface of an axial piston pump. The thickness of the lubricant film has a significant impact on the efficiency of the piston pump yet it still remains an uncertainty. If the lubricant film is too thin then friction will cause excessive damage resulting in deformation of interacting surfaces resulting in further uncertainty in thickness measurement. If the lubricant film is too thick then there is excessive leakage which will compromise the efficiency of the system. Acoustic ...
Characterization Of Nano-Porous Si-Cu Composites To Enhance Lubricant Retention Impacting The Tribological Properties Of Sliding Surfaces, 2015 University of Arkansas, Fayetteville
Characterization Of Nano-Porous Si-Cu Composites To Enhance Lubricant Retention Impacting The Tribological Properties Of Sliding Surfaces, Julius Sheldon Morehead
Theses and Dissertations
As the expectations for modern machinery's tribological and thermal performances continue to rise, the retention of lubricant on the contact surfaces of their sliding components becomes an increasingly important issue. Friction and wear cause heat-related failures which lead to catastrophic damage to machinery. Evaporation of a lubricant's volatile constituents as well as lubricant migration leads not only to a reduction in lubricant quantity but also in its quality, thus facilitating component failures. In order to enhance component reliability, the surface should incorporate features that actively retain lubricants. The unique properties of nano-porous topographies such as their high surface ...
Magnetic Bearings For Non-Destructive Health Monitoring Of Rotating Machinery Supported In Conventional Bearings, M. Kasarda, D, Quinn, T. Bash, D. Inman, R. Kirk, Jerzy Sawicki
Dr. D Dane Quinn
This paper describes initial results from a project expanding the field of rotor health monitoring by using Active Magnetic Bearings (AMBs) as actuators for applying a variety of known force inputs to a spinning rotor in order to monitor and evaluate response signals resulting from these inputs on-line. Similar to modal analysis and other nondestructive evaluation (NDE) techniques which apply input signals to static structures in order to monitor responses; this approach allows for the measurement of both input and output response in a rotating system for evaluation. However, unlike these techniques, the new procedure allows for multiple forms of ...
In-Vivo Corrosion And Fretting Of Modular Ti-6al-4v/Co-Cr-Mo Hip Prostheses: The Influence Of Microstructure And Design Parameters, 2015 Florida International University
In-Vivo Corrosion And Fretting Of Modular Ti-6al-4v/Co-Cr-Mo Hip Prostheses: The Influence Of Microstructure And Design Parameters, Jose Luis Gonzalez Jr
FIU Electronic Theses and Dissertations
The purpose of this study was to evaluate the incidence of corrosion and fretting in 48 retrieved titanium-6aluminum-4vanadium and/or cobalt-chromium-molybdenum modular total hip prosthesis with respect to alloy material microstructure and design parameters. The results revealed vastly different performance results for the wide array of microstructures examined. Severe corrosion/fretting was seen in 100% of as-cast, 24% of low carbon wrought, 9% of high carbon wrought and 5% of solution heat treated cobalt-chrome. Severe corrosion/fretting was observed in 60% of Ti-6Al-4V components. Design features which allow for fluid entry and stagnation, amplification of contact pressure and/or increased ...
A Comparison Between Graphene And Ws2 As Solid Lubricant Additives To Aluminum For Automobile Applications, 2015 Florida International University
A Comparison Between Graphene And Ws2 As Solid Lubricant Additives To Aluminum For Automobile Applications, Sara Rengifo
FIU Electronic Theses and Dissertations
The purpose of this thesis was to compare graphene nanoplatelets (GNP) and WS2 as solid lubricant additives to aluminum in order to reduce friction and wear. The central hypothesis of this work relied on lubricating properties of 2D materials, which consist layers that slip under a shear force.
Two aluminum composites were made (Al-2 vol.% GNP and Al-2 vol.% WS2) by spark plasma sintering. Tribological properties were evaluated by ball-on-disk wear tests at room temperature (RT) and 200°C.
WS2 not only presented the lowest COF (0.66) but also improved the wear resistance of aluminum by ...
Assessment Of The Wear Effects Of Alumina-Nanofluids On Heat-Exchanger Materials, 2015 Georgia Southern University
Assessment Of The Wear Effects Of Alumina-Nanofluids On Heat-Exchanger Materials, Fnu Aktaruzzaman
Electronic Theses and Dissertations
Nanofluids are nano-size-powder suspensions in liquids that are mainly studied for their abnormal thermal transport properties, and hence as enhanced alternatives to ordinary cooling fluids. The tribological effects of nanofluids are, however, largely unknown, in particular their likely wear and/or erosion effects, because of their interaction with cooling-system (heat-exchanger) materials. The thesis presents research to establish methodologies for testing and evaluating surface-change by nanofluid impact. The work is presented on development of novel test rigs and testing methodologies, and on the use of typical surface analysis tools for assessment of wear and erosion that may be produced by nanofluids ...
Investigation Of The Effect Of The Normal Load On The Incidence Of Friction Blisters In A Skin-Simulant Model, 2015 Iowa State University
Investigation Of The Effect Of The Normal Load On The Incidence Of Friction Blisters In A Skin-Simulant Model, Geetha Chimata, Christian J. Schwartz
Mechanical Engineering Publications
A laminar skin simulant was constructed to study the incidence of friction blisters. The skin simulant consists of a thin polyurethane top layer and textured gum foam rubber bottom layer adhered to an acrylic-backing plate to emulate the layered structure of the human skin. Friction blisters were produced on the skin simulant by using a dual-axis tribometer. The effect of the applied normal load on the number of cycles required to produce a blister was investigated. The skin simulant was also analyzed as an adhesive-bonded laminar composite to determine the relationship between the applied normal load and the number of ...