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Articles 1 - 30 of 64

Full-Text Articles in Mechanical Engineering

The Effects Of Surface Pace In Baseball, Jason Farlow May 2018

The Effects Of Surface Pace In Baseball, Jason Farlow

Senior Theses

A baseball travels across different surfaces at different paces. The goal of this experiment is to find a percentage difference in speeds the ball will reflect off a given surface. The energy lost on the turf surface was far more significant than on dirt surface as the turf lost an average of 26% of its energy as compared to just 16% of the energy on dirt. In the Northwest conference, teams play on four turf-based infields and five dirt-based infields. The results of this study suggest that kinetic friction forces are more significant in reducing ball rebound speed than in ...


Ultralow Wear Fluoropolymer Metal-Oxide Composites: Nanomechanics & Tribochemistry, Mark Alfred Sidebottom Jan 2018

Ultralow Wear Fluoropolymer Metal-Oxide Composites: Nanomechanics & Tribochemistry, Mark Alfred Sidebottom

Theses and Dissertations

Fluoropolymers and fluoropolymer composite materials are commonly used solid lubricant materials. Over the past fifteen years, the addition of nanostructured alumina particles to polytetrafluoroethylene (PTFE) was shown to improve the wear rate of unfilled PTFE by nearly 10,000x. In this work, the hardnesses of both porous and dense micron sized metal-oxide particles (alumina and CoAl2O4) were independently measured using in-situ nanoindentation experiments that correlated directly with wear rate of the PTFE-metal-oxide composites. Framework for developing ultralow wear of PTFE-nanostructured alumina composites was extended to melt processable perfluoroalkoxy polymer (PFA)-nanostructured alumina composites. These composites also exhibited a nearly 10 ...


Thermal-Fluid Dynamic Model Of Luge Steels, Brandon Stell Dec 2017

Thermal-Fluid Dynamic Model Of Luge Steels, Brandon Stell

Master's Theses and Project Reports

Luge is an Olympic sport in which athletes ride feet-first on sleds down an ice-covered track. Competitors spring from the starting position and accelerate their sled by paddling with spiked gloves against the ice surface. Once the Luger leaves the starting section, their downhill motion is solely propelled by the effects of gravity. Athletes compete, one after the other, for the fastest time. Runs can differ by as little as a thousandth of a second, meaning that every minor sled adjustment, change of line choice, and shift of body position is critical. In the past, the sport of Luge has ...


Coupled Phase Transformations And Plastic Flows Under Torsion At High Pressure In Rotational Diamond Anvil Cell: Effect Of Contact Sliding, Biao Feng, Valery I. Levitas Jun 2017

Coupled Phase Transformations And Plastic Flows Under Torsion At High Pressure In Rotational Diamond Anvil Cell: Effect Of Contact Sliding, Biao Feng, Valery I. Levitas

Valery I. Levitas

A three-dimensional large-sliding contact model coupled with strain-induced phase transformations (PTs) and plastic flow in a disk-like sample under torsion at high pressure in rotational diamond anvil cell (RDAC) is formulated and studied. Coulomb and plastic friction are combined and take into account variable parameters due to PT. Results are obtained for weaker, equal-strength, and stronger high pressure phases, and for three values of the kinetic coefficient in a strain-controlled kinetic equation and friction coefficient. All drawbacks typical of problem with cohesion are overcome, including eliminating mesh-dependent shear band and artificial plastic zones. Contact sliding intensifies radial plastic flow, which ...


Friction Test Machine, Alec J. Makowski, Megan Hardisty, Brandon L. Killian Jun 2017

Friction Test Machine, Alec J. Makowski, Megan Hardisty, Brandon L. Killian

Mechanical Engineering

Parker Aerospace is interested in collecting empirical data of friction coefficients for skewed roller bearings. A fixture will be designed, constructed and tested to allow a technician to quickly and easily measure the friction torque of a skew roller bearing with varying axial loads, geometries, lubricants, temperatures and rotational speeds in order to improve actuator efficiency.


Study Of The Temporal Characteristics Of Friction And Contact Behavior Encountered During Braille Reading, Matthew A. Darden, Christian J. Schwartz Apr 2017

Study Of The Temporal Characteristics Of Friction And Contact Behavior Encountered During Braille Reading, Matthew A. Darden, Christian J. Schwartz

Mechanical Engineering Publications

Beyond the sense of sight, the sense of touch is one of the primary ways that individuals experience their surrounding environment. Fundamentally understanding the relationship of skin-surface tribology and its elicited tactile attributes could provide a breakthrough in improving the ability to efficiently transmit tactile information to those who rely on the sense of touch to interact with their surroundings, such as the blind and visually impaired (BVI) community. The tactile language of braille has been adopted by the BVI community, employing configurations of raised dome-shape dots to convey what is ordinarily presented in text and image form. The coefficient ...


Friction And Environmental Sensitivity Of Molybdenum Disulfide: Effects Of Microstructure, John Francis Curry Jan 2017

Friction And Environmental Sensitivity Of Molybdenum Disulfide: Effects Of Microstructure, John Francis Curry

Theses and Dissertations

For nearly a century, molybdenum disulfide has been employed as a solid lubricant to reduce the friction and wear between surfaces. MoS2 is in a class of unique materials, transition metal dichalcogens (TMDC), that have a single crystal structure forming lamellae that interact via weak van der Waals forces. This dissertation focuses on the link between the microstructure of MoS2 and the energetics of running film formation to reduce friction, and effects of environmental sensitivities on performance. Nitrogen impinged MoS2 films are utilized as a comparator to amorphous PVD deposited MoS2 in many of the studies due to the highly ...


Computational Modeling Of Transient Processes During Run-In For Tribological Systems, Rob Morien Dec 2016

Computational Modeling Of Transient Processes During Run-In For Tribological Systems, Rob Morien

Theses and Dissertations

Understanding the frictional behavior of machine elements in mutual rolling or sliding contact is important for many engineering applications. When frictional sliding is initiated, the tribological system passes through several stages with each stage possessing its own unique frictional property. The initial transition process preceding stationary sliding is usually called “run-in”. During the run-in time interval, surface topographies of frictional contacts as well as lubricant distribution and surface tribofilms reorganize and adjust through asperity deformation and wear processes before reaching the steady state. This surface stability formed during run-in leads to an improvement in frictional performance during steady state operation ...


Numerical Modeling Of Heat Transfer And Material Flow During Friction Extrusion Process, Hongsheng Zhang Jun 2016

Numerical Modeling Of Heat Transfer And Material Flow During Friction Extrusion Process, Hongsheng Zhang

Theses and Dissertations

Friction extrusion process is a novel manufacturing process that converts low-cost metal precursors (e.g. powders and machining chips) into high-value wires with potential applications in 3D printing of metallic products. However, there is little existing scientific literature involving friction extrusion process until recently. The present work is to study the heat transfer and material flow phenomena during the friction extrusion process on aluminum alloy 6061 through numerical models validated by experimental measurements.

The first part is a study of a simplified process in which flow of a transparent Newtonian fluid in a cylindrical chamber caused by frictional contact with ...


Tribological Testing And Analysis Of Ionic Liquids As Candidate Anti-Wear Additives For Next-Generation Engine Lubricants, William Charles Barnhill May 2016

Tribological Testing And Analysis Of Ionic Liquids As Candidate Anti-Wear Additives For Next-Generation Engine Lubricants, William Charles Barnhill

Masters Theses

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 ...


Friction And Wear Measurements In Automatic Transmission Clutch, Steffen Harm, Dabin Kim, Jean Paulo Mulles, Eric Stavitzski, Hoang Tran Jan 2016

Friction And Wear Measurements In Automatic Transmission Clutch, Steffen Harm, Dabin Kim, Jean Paulo Mulles, Eric Stavitzski, Hoang Tran

Capstone Design Expo Posters

In order to create alternate pathways to increase fuel efficiency, flexible ways to alter and test fluid properties are needed when transmission manufacturers change the operating conditions or components used in automatic transmissions. A prototype was fabricated to satisfy this need by reducing the cost, time of conducting tests while producing accurate results, and also increasing the amount of trials that can be conducted in a laboratory setting. The limitations of developing a new prototype are: safety, weight, ease of use, laboratory size, and establishing accurate results within the amount of time given. This project was approached using the Engineering ...


The Effects Of Micro-Dimple Texture On The Friction And Thermal Behavior Of A Point Contact, Utsav Kamleshbhai Parmar Jan 2016

The Effects Of Micro-Dimple Texture On The Friction And Thermal Behavior Of A Point Contact, Utsav Kamleshbhai Parmar

Browse all Theses and Dissertations

This study investigates the effects of the micro-dimple texture on the friction and surface temperature performances of a ball-on-disk contact, operating under the speed and load ranges that cover typical gearing applications. Circular shaped micro-dimple arrays with different dimple center distances and dimple depths are implemented on the ball surface to quantify the impacts of these two parameters on the friction coefficient and the maximum ball surface temperature. In addition, the contacts of three surface texture combinations, namely micro-dimpled and polished ball surface versus polished disk surface, polished ball surface versus polished disk surface and ground ball surface versus ground ...


Hybrid Manufacturing Processes For Fusion Welding And Friction Stir Welding Of Aerospace Grade Aluminum Alloys, Megan Alexandra Gegesky Jan 2016

Hybrid Manufacturing Processes For Fusion Welding And Friction Stir Welding Of Aerospace Grade Aluminum Alloys, Megan Alexandra Gegesky

Masters Theses

"Friction stir welding and processing can provide for joints in aerospace grade aluminum alloys that have preferable material properties as compared to fusion welding techniques. Aerospace grade aluminum alloys such as AA2024-T3 and AA7075-T6 are considered non-weldable by traditional fusion welding techniques. Improved mechanical properties over previously used techniques are usually preferable for aerospace applications. Therefore, by combining traditional fusion welding and friction stir processing techniques, it could be plausible to create more difficult geometries in manufactured parts instead of using traditional techniques. While this combination of fusion welding and friction stir processing is not a new technology, its introduction ...


An Investigation Of Skin Tribology Phenomena Involved In Tactile Communication Through Braille And Its Associated Psychophysical Response During Task-Based Discrimination, Matthew Aguirre Darden Jan 2016

An Investigation Of Skin Tribology Phenomena Involved In Tactile Communication Through Braille And Its Associated Psychophysical Response During Task-Based Discrimination, Matthew Aguirre Darden

Graduate Theses and Dissertations

Most individuals utilize all five senses, especially their sense of sight, to create a unique sensory experience depicting the surrounding environment. Unfortunately, individuals in the blind and visually impaired (BVI) community lack the sense of sight and rely primarily on tactile means to acquire valuable or potentially vital information, leading to the advent of tactile communication methods like braille. A key challenge in controlling the haptic experience of a surface is the lack of fundamental understanding of how various surface attributes, such as friction and texture, affect the tactile response. Oftentimes, braille users experience tactile confusion when scanning complex tactual ...


Development Of Durable Superhydrophobic Materials For Ice- And Snow-Free Airport Concrete Pavements, Therin Jamal Young Jan 2016

Development Of Durable Superhydrophobic Materials For Ice- And Snow-Free Airport Concrete Pavements, Therin Jamal Young

Graduate Theses and Dissertations

Superhydrophobic surfaces that mimic surfaces found in nature, such as the lotus leaf, are an attractive research topic in various fields of study because of their numerous applications. More recent studies have focused on superhydrophobic surfaces that reduce or completely stop the accretion of ice and snow on power lines and aircraft that operate in cold regions. The superhydrophobic phenomena is usually achieved by creating a dual-scale roughness that is composed of micro- and nano-scale structures that trap air in-between themselves and reduce the surface energy of the textured surface. The objective of this study was to assess the tribological ...


Skin Tribology Phenomena Associated With Reading Braille Print: The Influence Of Cell Patterns And Skin Behavior On Coefficient Of Friction, Matthew A. Darden, Christian J. Schwartz May 2015

Skin Tribology Phenomena Associated With Reading Braille Print: The Influence Of Cell Patterns And Skin Behavior On Coefficient Of Friction, Matthew A. Darden, Christian J. Schwartz

Mechanical Engineering Publications

Efficient transmission of tactile information is vital for individuals who rely on their sense of touch to interact with and navigate their surroundings, including visually impaired persons. Somatosensory phenomena have been investigated with respect to surface topologies and neuron sensitivities in the skin, but there is little knowledge of the specific skin tribology when reading tactual-coded information such as braille. Braille is a tactual code that employs raised dome-shaped dots in six-position cells (2 columns by 3 rows per cell), with various dot patterns representing individual text characters, punctuation or mathematical operators. Due to the hypothesized significance of friction on ...


Stress Response Of A Rubber Block With Frictional Contact Under Axial Loading, J. Suh, S. Kelly Apr 2015

Stress Response Of A Rubber Block With Frictional Contact Under Axial Loading, J. Suh, S. Kelly

Dr. S. Graham Kelly

Rubber blocks (or springs) are structural components widely used in many applications. Design characteristics of a rubber block under axial loading are an apparent modulus (or compression modulus) and normal and shear stresses on contact surfaces. These are affected by a contact condition of the rubber block in contact with two rigid plates and the shape of the block. The problem of a rubber block bonded to two rigid plates has been solved using various approaches. In contrast, for a rubber block whose one surface is bonded to a rigid plate and the other surface in contact with a frictional ...


Analysis Of High Frequency Squeal In A Disc-Brake System Using A Stick-Slip Friction Model, Manish Paliwal, Ajay Mahajan, Peter Filip Apr 2015

Analysis Of High Frequency Squeal In A Disc-Brake System Using A Stick-Slip Friction Model, Manish Paliwal, Ajay Mahajan, Peter Filip

Dr. Ajay Mahajan

This paper presents a two degree of freedom (2-DOF) stick-slip friction model for studying the effect of contact stiffness on the stability of the system. It is shown that the stability is not only a function of non-linear variation in the friction force provide by stick-slip but also depends on the variation in stiffness of contact due to the formation of friction layers on the surface of the rotor and the brake pad. Parametric studies have been presented to show the effect of variation in coefficient of friction and contact stiffness on the system stability.


High Regression Rate Hybrid Rocket Fuel Grains With Helical Port Structures, Stephen A. Whitmore, Sean D. Walker, Daniel P. Merkley, Mansour Sobbi Jan 2015

High Regression Rate Hybrid Rocket Fuel Grains With Helical Port Structures, Stephen A. Whitmore, Sean D. Walker, Daniel P. Merkley, Mansour Sobbi

Mechanical and Aerospace Engineering Faculty Publications

Results froma development campaign, where modern additive manufacturing methods are used to fabricate hybrid rocket fuel grains with embedded helical ports, are presented. The fuel grains were constructed from acrlyonitrile butadiene styrene using commercially available three-dimensional printer feedstockmaterial.Gaseous oxygen is used as the oxidizer for this test campaign.When compared to cylindrical fuel ports, significant increases in fuel regression rates were observed, and these increases in regression rate diminished with time as the helical fuel port burns to become progressivelymore cylindrical. Comparisons to the helical pipe flow skin friction correlation developed by Mishra and Gupta indicate that increased skin ...


Mechanisms Controlling Friction And Adhesion At The Atomic Length-Scale, Xin Zhou Liu Jan 2015

Mechanisms Controlling Friction And Adhesion At The Atomic Length-Scale, Xin Zhou Liu

Publicly Accessible Penn Dissertations

A lack of understanding of the fundamental mechanisms governing atomic-scale adhesion and friction creates ongoing challenges as technologically-relevant devices are miniaturized. One major class of failure mechanisms of such devices results from high friction, adhesion, and wear. This thesis presents investigations into methods by which atomic-scale friction and adhesion can be controlled. Using atomic force microscopy (AFM), friction and adhesion properties of graphene were examined. While friction between the tip and graphene depends on thickness, as explained by the â??puckering effectâ??, adhesion is independent of the thickness when measured conventionally. However, adhesion is transiently higher when measured after the ...


On The Nonlinear Tribological Jerk Dynamics At Sliding Interfaces, Divyeshkumar Patel Dec 2014

On The Nonlinear Tribological Jerk Dynamics At Sliding Interfaces, Divyeshkumar Patel

Theses and Dissertations

As the world desires the next industrial revolution, the potential threats that will undermine energy efficient innovations include detrimental frictional effects that exacerbate wear, hasten equipment breakdowns, and worsen heat dissipation. Capturing the inherently nonlinear manifestations of friction fundamentally has been difficult. A fundamental modeling scheme elucidating friction will bolster novel technologies synthesizing wear resistant materials and lubricants needed for sustainable energy efficiency.

Frictional dissipation at dynamical sliding interfaces has been studied for generations. Interfacial sliding frictional effects are prevalent in natural and artificial phenomena such as earthquake, hip and knee joints, and the moving parts of energy-producing and energy-consuming ...


Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford Dec 2014

Wear Resistant Polydopamine/Ptfe Nanoparticle Composite Coating For Dry Lubrication Applications, Samuel George Beckford

Theses and Dissertations

This dissertation presents an investigation into the effect of nanoparticle fillers and a polydopamine adhesive primer on the tribological performance of thin PTFE films. The principal objective of this investigation was to reduce wear in PTFE films, an issue which precludes the use of PTFE films in tribological applications requiring high durability. The friction and wear of the composite films were evaluated using a ball-on-flat configuration in linear reciprocating motion. It was found that the use of a polydopamine adhesive primer reduces the wear of PTFE films more than 600 times. X-ray photoelectron spectroscopy (XPS) results show that a tenacious ...


Friction Test Machine, Kyle Raymon Schless, Lynda Beatriz Tesillo, Mustapha Nadri Jun 2014

Friction Test Machine, Kyle Raymon Schless, Lynda Beatriz Tesillo, Mustapha Nadri

Mechanical Engineering

No abstract provided.


Modeling Of Instabilities And Self-Organization At The Frictional Interface, Vahid Mortazavi May 2014

Modeling Of Instabilities And Self-Organization At The Frictional Interface, Vahid Mortazavi

Theses and Dissertations

The field of friction-induced self-organization and its practical importance remains unknown territory to many tribologists. Friction is usually thought of as irreversible dissipation of energy and deterioration; however, under certain conditions, friction can lead to the formation of new structures at the interface, including in-situ tribofilms and various patterns at the interface.

This thesis studies self-organization and instabilities at the frictional interface, including the instability due to the temperature-dependency of the coefficient of friction, the transient process of frictional running-in, frictional Turing systems, the stick-and-slip phenomenon, and, finally, contact angle (CA) hysteresis as an example of solid-liquid friction and dissipation ...


Tribological Behaviour Of H- And W-Dlc Coatings: Effects Of Environment And Temperature On Adhesion, Ahmed Abou Gharam Jan 2014

Tribological Behaviour Of H- And W-Dlc Coatings: Effects Of Environment And Temperature On Adhesion, Ahmed Abou Gharam

Electronic Theses and Dissertations

The objective of this study was to gain insight into the friction, aluminum adhesion, and wear mechanisms of diamond-like carbon (DLC) coatings, and to provide guidelines for coating design and development. Mechanisms that control the tribological behaviour of DLC coatings and the effects of dopants (i.e. hydrogen (H-DLC), and tungsten (W-DLC)) against aluminum alloys were investigated under various environments and test temperatures. The effects of temperature and an oxygen-rich environment on dopant-free DLC, H- DLC, and W- DLC were investigated. Experimental analyses of dopant-free DLC showed that, when it was tested in an atmosphere consisting of 50% oxygen and ...


Energy And Thermodynamically Based Approaches For Analysis Of Damage In Contact Problems, Afshin Babaie Aghdam Jan 2014

Energy And Thermodynamically Based Approaches For Analysis Of Damage In Contact Problems, Afshin Babaie Aghdam

LSU Doctoral Dissertations

A novel methodology for analysis of damage in contact problems in presented. Two important categories of contact damage are studied, namely crack nucleation and adhesive wear. The proposed methodology is primarily based on the laws of energy and thermodynamics, and as such offers great advantages by unifying the analysis of damage in a variety of contact configurations. Crack nucleation is the first damage type analyzed. For this purpose, the line-contact fretting configuration is chosen. A thermodynamically-based continuum damage mechanics (CDM) approach is employed. Intense stress gradients in the contact region are found to be highly influential in the crack nucleation ...


Enamel Insulated Copper Wire In Electric Motors: Sliding Behavior And Possible Damage Mechanisms During Die Bending, Albion Demiri Jan 2014

Enamel Insulated Copper Wire In Electric Motors: Sliding Behavior And Possible Damage Mechanisms During Die Bending, Albion Demiri

Electronic Theses and Dissertations

This study investigates the sliding friction and the forming behaviour of enamel insulated copper wire during the die-forming process. It also aims to determine potential damage mechanisms to the wire during bending process for electric motor coils. In this investigation a wire-bending machine was designed and built in order to simulate the wire forming process in a laboratory scale. Bending angle of the wire and the bending radii were used to control the strain on the wire surface. The effect of speed on COF was investigated for different speeds of of 1, 5, 10, 15, and 20mm/s. A positive ...


An Experimental Investigation Characterizing The Tribological Performance Of Natural And Synthetic Biolubricants Composed Of Carboxylic Acids For Energy Conservation And Sustainability, Carlton Jonathan Reeves Dec 2013

An Experimental Investigation Characterizing The Tribological Performance Of Natural And Synthetic Biolubricants Composed Of Carboxylic Acids For Energy Conservation And Sustainability, Carlton Jonathan Reeves

Theses and Dissertations

Over the last several decades the lubrication industry has been striving to bring bio-based lubricants known as biolubricants to prominence. The reasons for the increased environmental initiatives are due to depletion of oil reserves, increases in oil price, stringent government regulations on petroleum-based oils, and most importantly, concerns for protecting the environment. With an estimated, 50% of all lubricants entering the environment and much of these being composed of toxic mineral oils, biolubricants have begun to witness a resurgence. This experimental investigation seeks to develop a new class of ecofriendly biolubricants that are less toxic to the environment, derived from ...


Motion And Force Transmission Of A Flexible Instrument Inside A Curved Endoscope, Jitendra P. Khatait Sep 2013

Motion And Force Transmission Of A Flexible Instrument Inside A Curved Endoscope, Jitendra P. Khatait

Jitendra P Khatait

Flexible instruments are increasingly used to perform advanced and complex surgical procedures either manually or robotically. The success of flexible instruments in surgery requires high motion and force fidelity, and controllability of the tip. However, the friction and the limited stiffness of such instruments limit their motion and force transmission. The implementation of flexible instruments in surgery necessitates their characterization, the development of proper tools to understand the effect of various mechanical parameters on their overall performance, and an improvement in motion and force fidelity. Therefore, this thesis describes 2-D and 3-D flexible multibody models of a flexible surgical instrument ...


Plastic Flows And Phase Transformations In Materials Under Compression In Diamond Anvil Cell: Effect Of Contact Sliding, Biao Feng, Valery I. Levitas, Oleg M. Zarechnyy Jul 2013

Plastic Flows And Phase Transformations In Materials Under Compression In Diamond Anvil Cell: Effect Of Contact Sliding, Biao Feng, Valery I. Levitas, Oleg M. Zarechnyy

Aerospace Engineering Publications

Modeling of coupled plastic flows and strain-induced phase transformations (PTs) under high pressure in a diamond anvil cell is performed with the focus on the effect of the contact sliding between sample and anvils. Finite element software ABAQUS is utilized and a combination of Coulomb friction and plastic friction is considered. Results are obtained for PTs to weaker, equal-strength, and stronger high pressure phases, using different scaling parameters in a strain-controlled kinetic equation, and with various friction coefficients. Compared to the model with cohesion, artificial shear banding near the constant surface is eliminated. Sliding and the reduction in friction coefficient ...