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Theses and Dissertations

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Full-Text Articles in Applied Mechanics

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller May 2019

Predicting The Mechanical Properties Of Nanocomposites Reinforced With 1-D, 2-D And 3-D Nanomaterials, Scott Edward Muller

Theses and Dissertations

Materials with features at the nanoscale can provide unique mechanical properties and increased functionality when included as part of a nanocomposite. This dissertation utilizes computational methods at multiple scales, including molecular dynamics (MD) and density functional theory (DFT), and the coupled atomistic and discrete dislocation multiscale method (CADD), to predict the mechanical properties of nanocomposites possessing nanomaterials that are either 1-D (carbyne chains), 2-D (graphene sheets), or 3-D (Al/amorphous-Si core-shell nanorod).

The MD method is used to model Ni-graphene nanocomposites. The strength of a Ni-graphene nanocomposite is found to improve by increasing the gap between the graphene sheet and ...


Motor Control Systems Analysis, Design, And Optimization Strategies For A Lightweight Excavation Robot, Austin Jerold Crawford May 2019

Motor Control Systems Analysis, Design, And Optimization Strategies For A Lightweight Excavation Robot, Austin Jerold Crawford

Theses and Dissertations

This thesis entails motor control system analysis, design, and optimization for the University of Arkansas NASA Robotic Mining Competition robot. The open-loop system is to be modeled and simulated in order to achieve a desired rapid, yet smooth response to a change in input. The initial goal of this work is to find a repeatable, generalized step-by-step process that can be used to tune the gains of a PID controller for multiple different operating points. Then, sensors are to be modeled onto the robot within a feedback loop to develop an error signal and to make the control system self-corrective ...


Computational And Experimental Investigation On The Wetting Behavior Of Droplet-Fiber Systems, Hossain Aziz Jan 2019

Computational And Experimental Investigation On The Wetting Behavior Of Droplet-Fiber Systems, Hossain Aziz

Theses and Dissertations

Interaction of a liquid droplet and a fiber or layer of fibers is ubiquitous in nature and in a variety of industrial applications. It plays a crucial role in fog harvesting, coalescence filtration, membrane desalination, self-cleaning and fiber based microfluidics, among many others. This work presents a quantitative investigation on the interactions of a droplet with a fiber or layers of fibers. More precisely, the present work is focused on 1) predicting the effects of fiber’s size and material on its ability to withhold a droplet against external forces and on the liquid residue left on the fiber after ...


The Effect Of Incorporating End-User Customization Into Additive Manufacturing Designs, Jonathan D. Ashley Dec 2018

The Effect Of Incorporating End-User Customization Into Additive Manufacturing Designs, Jonathan D. Ashley

Theses and Dissertations

In the realm of additive manufacturing there is an increasing trend among makers to create designs that allow for end-users to alter them prior to printing an artifact. Online design repositories have tools that facilitate the creation of such artifacts. There are currently no rules for how to create a good customizable design or a way to measure the degree of customization within a design. This work defines three types of customizations found in additive manufacturing and presents three metrics to measure the degree of customization within designs based on the three types of customization. The goal of this work ...


Microheater Array Powder Sintering (Maps) For Printing Flexible Electronics, Nicholas Holt May 2018

Microheater Array Powder Sintering (Maps) For Printing Flexible Electronics, Nicholas Holt

Theses and Dissertations

Microheater array powder sintering (MAPS) is a novel additive manufacturing process that uses an array of microheaters to selectively sinter powder particles. MAPS shows great promise as a new method of printing flexible electronics by enabling digital curing of conductive inks on a variety of substrates. MAPS operation relies on establishing a precision air gap of a few microns between an array of microheaters, which can reach temperatures of 600°C, and a layer of conductive ink which can be deposited onto a flexible substrate. This system presents challenges, being: the fabrication of a microheater that can reach suitable temperatures ...


Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi May 2018

Phase Transitions In Monochalcogenide Monolayers, Mehrshad Mehboudi

Theses and Dissertations

Since discovery of graphene in 2004 as a truly one-atom-thick material with extraordinary mechanical and electronic properties, researchers successfully predicted and synthesized many other two-dimensional materials such as transition metal dichalcogenides (TMDCs) and monochalcogenide monolayers (MMs). Graphene has a non-degenerate structural ground state that is key to its stability at room temperature. However, group IV monochalcogenides such as monolayers of SnSe, and GeSe have a fourfold degenerate ground state. This degeneracy in ground state can lead to structural instability, disorder, and phase transition in finite temperature. The energy that is required to overcome from one degenerate ground state to another ...


Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed Aug 2016

Design Maps For Fracture Resistant Functionally Graded Materials, Muhammad Ridwan Murshed

Theses and Dissertations

The objective of this research is to generate design maps to identify functionally graded microstructures with enhanced fracture toughness. Several Functionally Graded Materials (FGMs) with an edge crack and membrane loading are considered and the resulting J-integral values are computed numerically using Finite Element Analysis. In order to capture the resulting stress fields accurately, Barsoum elements are used in the vicinity of the crack tip and the simulations are carried out for several crack lengths (a) and material contrasts (κ). The averages of the J-integral values are used to determine the normalized Stress Intensity Factors which are then benchmarked with ...


Modeling Time-Dependent Performance Of Submerged Superhydrophobic Or Slippery Surfaces, Ahmed A. Hemeda Jan 2016

Modeling Time-Dependent Performance Of Submerged Superhydrophobic Or Slippery Surfaces, Ahmed A. Hemeda

Theses and Dissertations

The goal of this study is to quantify the transient performance of microfabricated superhydrophobic surfaces when used in underwater applications. A mathematical framework is developed and used to predict the stability, longevity, and drag reduction benefits of submerged superhydrophobic surfaces with two- or three-dimensional micro-textures. In addition, a novel design is proposed to improve the drag-reduction benefits of lubricant-infused surfaces, by placing a layer of trapped air underneath the lubricant layer. The new design is referred to as lubricant–infused surfaces with trapped air, and it is designed to eliminate the long-lasting longevity problem of submerged superhydrophobic surfaces. The effectiveness ...


Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew Dec 2015

Investigation Of A Numerical Algorithm For A Discretized Rubber-Belt Continuously Variable Transmission Dynamic Model And Techniques For The Measurement Of Belt Material Properties., Brian Gene Ballew

Theses and Dissertations

A numerical algorithm for modeling the dynamic response of a rubber-belt Continuously Variable Transmission (CVT) belt is recreated. The numerical attributes applied to the algorithm and difficulties with numerical stability are discussed in detail. The degrees of freedom of the system have been expanded to include the dynamics of the engine torque output and vehicle loads such as rolling resistance and aerodynamic drag. This was done to emphasize the use of the model as an analysis tool for simulating CVT/engine/vehicle response. The increased degrees of freedom require the addition of a linear dampening element between belt nodes to ...


Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows Jul 2015

Traction-Separation Relationships For Hydrogen-Induced Grain Boundary Embrittlement In Nickel Via Molecular Dynamics Simulations, Wesley Allen Barrows

Theses and Dissertations

The deleterious effects of atomic and molecular hydrogen on the mechanical properties of metals have long been observed. Although several theories exist describing the mechanisms by which hydrogen negatively influences the failure of materials, a consensus has yet to be reached regarding the exact mechanism or combination of mechanisms. Two mechanisms have gained support in explaining hydrogen’s degradative role in non-hydride forming metals: hydrogen-enhanced localized plasticity and hydrogen-enhanced decohesion. Yet, the interplay between these mechanisms and microstructure in metallic materials has not been explained. Accordingly, for this thesis, the three main objectives are: (i) to develop a numerical methodology ...


Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson Dec 2014

Highly Transparent, Self-Cleaning, And Antireflective Nanoparticle Coatings, Corey Seth Thompson

Theses and Dissertations

Current solar panel technologies require a sheet of glass to serve as both mechanical support and to protect the cells from the environment. The reflection from the glass sheet can reflect up to 8% of the incident light, reducing the power output of the panel. Antireflective coatings can be used to allow more light to enter the panel to be converted into usable electricity. However, no solid thin film materials exhibit a low enough index of refraction to serve as antireflective coatings for common solar glass. The main goal of this research was to investigate the self-cleaning, antifogging, and antireflective ...


Utilizing Failure Information For Mission Assessment And Optimization For Complex Systems, Charlie Destefano Dec 2014

Utilizing Failure Information For Mission Assessment And Optimization For Complex Systems, Charlie Destefano

Theses and Dissertations

This paper presents a new failure analysis method, Failure Identification for Mission Analysis (FIMA), which performs a general failure analysis for the overall state of a system, as well as a mission-specific analysis that identifies how failures may have differing effects on the various mission tasks that a system must complete. The FIMA method is capable of being implemented at any point in the design process. During early design stages, the FIMA method will identify various qualitative failure scenarios based on programmed functional relationships and any number of initial failures wished to be simulated. The functional relationships for this method ...


Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman Aug 2014

Atomistic Simulation And Virtual Diffraction Characterization Of Alumina Interfaces: Evaluating Structure And Stability For Predictive Physical Vapor Deposition Models, Shawn Patrick Coleman

Theses and Dissertations

The objectives of this work are to investigate the structure and energetic stability of different alumina (Al2O3) phases using atomistic simulation and virtual diffraction characterization. To meet these objectives, this research performs molecular statics and molecular dynamics simulations employing the reactive force-field (ReaxFF) potential to model bulk, interface, and surface structures in the θ-, γ-, κ-, and α-Al2O3 system. Simulations throughout this study are characterized using a new virtual diffraction algorithm, developed and implemented for this work, that creates both selected area electron diffraction (SAED) and x-ray diffraction (XRD) line profiles without assuming prior ...


Electroencephalography(Eeg) Data Collection And Processing Through Machine Learning, Jayshree Desai Aug 2014

Electroencephalography(Eeg) Data Collection And Processing Through Machine Learning, Jayshree Desai

Theses and Dissertations

Machine learning methods are an excellent way for understanding the neural basis of human decision making. Some machine learning systems try to eradicate the need for human intuition in data analysis whereas others embrace a collective approach between humans and machines. The objective of this project is to collect Electroencephalography (EEG) signals through wireless sensors, and the process the collected signals through machine learning methods. The EEG data is collected using three EEG electrodes, each being the positive, negative and ground terminals respectively. Since the signal measures in the unit of micro-volts it needs to be amplified using amplifier circuit ...


Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary Dec 2013

Crack Growth Behavior Under Creep-Fatigue Conditions Using Compact And Double Edge Notch Tension-Compression Specimens, Santosh B. Narasimha Chary

Theses and Dissertations

The American Society for Testing and Materials (ASTM) has recently developed a new standard for creep-fatigue crack growth testing, E 2760-10, that supports testing compact specimens, C(T), under load controlled conditions. C(T) specimens are commonly used for fatigue and creep-fatigue crack growth testing under constant-load-amplitude conditions. The use of these specimens is limited to positive load ratios. They are also limited in the amount of crack growth data that can be developed at high stress intensity values due to accumulation of plastic and/or creep strains leading to ratcheting in the specimen. Testing under displacement control can potentially ...


Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita May 2013

Design And Fundamental Understanding Of Minimum Quantity Lubrication (Mql) Assisted Grinding Using Advanced Nanolubricants, Parash Kalita

Theses and Dissertations

Abrasive grinding is widely used across manufacturing industry for finishing parts and components requiring smooth superficial textures and precise dimensional tolerances and accuracy. Unlike any other machining operations, the complex thermo-mechanical processes during grinding produce excessive friction-induced energy consumption, heat, and intense contact seizures. Lubrication and cooling from grinding fluids is crucial in minimizing the deleterious effects of friction and heat to maximize the output part quality and process efficiency. The conventional flood grinding approach of an uneconomical application of large quantities of chemically active fluids has been found ineffective to provide sufficient lubrication and produces waste streams and pollutants ...


Triz Applied In Product Development Project Prioritization, Frank Heinsohn Jan 2005

Triz Applied In Product Development Project Prioritization, Frank Heinsohn

Theses and Dissertations

No abstract provided.


Dynamic Analysis Of The Interface Stress And Spallation In Coated Materials, Jong-Ho Kim Jan 1996

Dynamic Analysis Of The Interface Stress And Spallation In Coated Materials, Jong-Ho Kim

Theses and Dissertations

No abstract provided.


Leakage And Swirl Velocities In Labyrinth Seals, Uågur Yèucel Jan 1996

Leakage And Swirl Velocities In Labyrinth Seals, Uågur Yèucel

Theses and Dissertations

No abstract provided.


A Two Stage Approach For Improving Hospital Inpatient Operations Efficiency, Wen-Yen Chen Jan 1995

A Two Stage Approach For Improving Hospital Inpatient Operations Efficiency, Wen-Yen Chen

Theses and Dissertations

No abstract provided.


Experimental Analysis Of Light Vehicle Frame Structure, Terry L. Stertzel Jan 1995

Experimental Analysis Of Light Vehicle Frame Structure, Terry L. Stertzel

Theses and Dissertations

No abstract provided.


Design And Deployment Of A Quality Management System : A Case Study Of Rv Industries, Inc., Octavio C. Siochi Jan 1994

Design And Deployment Of A Quality Management System : A Case Study Of Rv Industries, Inc., Octavio C. Siochi

Theses and Dissertations

No abstract provided.


Environmentally Enhanced Thermal Fatigue And Cracking Of A Gamma- Based Titanium Aluminide Alloy, William D. Dunfee Jan 1994

Environmentally Enhanced Thermal Fatigue And Cracking Of A Gamma- Based Titanium Aluminide Alloy, William D. Dunfee

Theses and Dissertations

No abstract provided.


Optimization Study Of Agv System Design, Susan Ann Dick Jan 1993

Optimization Study Of Agv System Design, Susan Ann Dick

Theses and Dissertations

No abstract provided.


Effect Of Loading Rate On Thermodynamic Equilibrium Stress/Strain States Of Uniaxial Test Specimens, Chao-Hsin Wang Jan 1993

Effect Of Loading Rate On Thermodynamic Equilibrium Stress/Strain States Of Uniaxial Test Specimens, Chao-Hsin Wang

Theses and Dissertations

No abstract provided.


A Study Of Environmentally Enhanced Creep Crack Growth In Inconel 718 Alloy, Paul F. Valerio Jan 1993

A Study Of Environmentally Enhanced Creep Crack Growth In Inconel 718 Alloy, Paul F. Valerio

Theses and Dissertations

No abstract provided.


Transient Stress And Failure Analysis Of 105 Mm Gun Barrel Caused By Projectile Premature, Chi-Jui Huang Jan 1993

Transient Stress And Failure Analysis Of 105 Mm Gun Barrel Caused By Projectile Premature, Chi-Jui Huang

Theses and Dissertations

No abstract provided.


Assessment Of Bearing Load Alignment On Fracture Site In Dovetail Section Of Turbine Rotor, Bing-Tang Fan Jan 1993

Assessment Of Bearing Load Alignment On Fracture Site In Dovetail Section Of Turbine Rotor, Bing-Tang Fan

Theses and Dissertations

No abstract provided.


Direct Numerical Simulation Of Interfacial Instability In Stratified Newtonian Fluids, David Michael Rakos Jan 1992

Direct Numerical Simulation Of Interfacial Instability In Stratified Newtonian Fluids, David Michael Rakos

Theses and Dissertations

No abstract provided.


Instantaneous Structure Of Vortex Breakdown On A Delta Wing, Joseph Towfighi Jan 1992

Instantaneous Structure Of Vortex Breakdown On A Delta Wing, Joseph Towfighi

Theses and Dissertations

No abstract provided.