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Full-Text Articles in Mechanical Engineering

Use Of A Triboelectric Generator For A Tunable Wideband Energy Harvester And A Threshold Shock Sensor, Daniel S. Nelson Jul 2018

Use Of A Triboelectric Generator For A Tunable Wideband Energy Harvester And A Threshold Shock Sensor, Daniel S. Nelson

Graduate Dissertations and Theses

The prevalence of triboelectricity as a transduction mechanism has increased rapidly in recent years. We will discuss two uses for triboelectric generators. One design is a tunable wideband energy harvester. An axial force and amplitude limiter work together to create an energy harvester that can accommodate various frequency sources and have a large operating bandwidth. The addition of the compressive axial force also softens the system, which allows for higher voltage outputs. A proof of concept of a threshold shock sensor is proposed that incorporates bi-stability along with the triboelectric effect. A clamped-clamped buckled beam will switch stable states when ...


Multi-Objective Design Optimization Of Reverse Total Shoulder Arthroplasty To Maximize Range Of Motion And Joint Stability, Josie A. Elwell Jul 2018

Multi-Objective Design Optimization Of Reverse Total Shoulder Arthroplasty To Maximize Range Of Motion And Joint Stability, Josie A. Elwell

Graduate Dissertations and Theses

Reverse total shoulder arthroplasty was developed to restore range of motion (ROM) and joint stability to patients with pre-operative conditions that are not addressed by conventional replacements. Although reverse total shoulder arthroplasty is the current gold standard for treating a range of indications, the effects of varying its design on functional outcomes of the procedure are still not well understood.

To that end, it is not yet clear which configurations, in terms of both design and surgical placement parameters, maximize range of motion and stability of the joint. It was hypothesized that there is trade-off between the two. These types ...


Investigation Of Small-Scale Thermal Recovery And Storage Systems, Suvhashis Thapa Jul 2018

Investigation Of Small-Scale Thermal Recovery And Storage Systems, Suvhashis Thapa

Doctoral Dissertations

An approach to recover and store waste heat is presented in this dissertation. The waste heat is the energy that is rejected to the environment without being put to practical use and it is a result of both equipment inefficiency and thermodynamic limitation on the equipment and the process. In a typical Otto cycle, for instance, out of the total energy consumed by the system, only one-third of the energy is converted into useful work and the rest is discharged in the environment as waste heat [1]. For a spark ignition, a 1.4 liters internal combustion engine with the ...


Design And Synthesis Of Novel Nanometallic Catalysts And Electrode Materials For Green Fuel Cells, Jing Zhang May 2018

Design And Synthesis Of Novel Nanometallic Catalysts And Electrode Materials For Green Fuel Cells, Jing Zhang

Graduate Dissertations and Theses

The United Nations formally adopted 17 sustainable development goals (SDGs) at its 2015 summit. Many of these goals addressed issues such poverty, hunger, health, education, climate-change, gender equality, water, sanitation, energy, urbanization, environment and social justice. The seventh SDG seeks to ensure access to affordable, reliable, sustainable and modern energy for all. So among all renewable forms of energy, fuel cells with high efficiency have attracted a lot of attention recently. In particular, the direct ethanol fuel cells (DEFCs) and microbial fuel cells (MFCs) are significant due to their green fuel, less waste generated and environmental friendliness. Hence the overall ...


Mechanical Reinforcement Of Polyacrylamide Hydrogels Using Pristine Single-Walled Carbon Nanotubes, Wuxiang Feng May 2018

Mechanical Reinforcement Of Polyacrylamide Hydrogels Using Pristine Single-Walled Carbon Nanotubes, Wuxiang Feng

Graduate Dissertations and Theses

Hydrogels have great promise as an innovative biomedical material possessing many advantages such as high water content, porous structure, and excellent biocompatibility. Although hydrogels have been used to develop some successful applications, they commonly do not have sufficient mechanical strength required for artificial soft tissues. Here, the author fabricated reinforced PAAm hydrogels using single-walled carbon nanotubes as reinforcing materials. The fusion of SWCNTs and the PAAm matrix successfully generated SWCNTs/PAAm hybrid gels with improved mechanical strength. Moreover, the aqueous dispersion of SWCNTs used for engineering the hybrid gels remained excellent stability after two months. SEM images from previous research ...


Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance May 2017

Computer Simulation Of Pore Migration Due To Temperature Gradients In Nuclear Oxide Fuel, Ian Wayne Vance

Theses and Dissertations

A phase-field simulation model is being presented that captures the thermal-gradient-driven migration of pores in oxide fuel associated with fuel restructuring. The model utilizes a Cahn-Hilliard equation supplemented with an advection term to describe the vapor transport of fuel material through the pore interior due to gradients in vapor pressure. In addition, the model also captures changes in a migrating pores’ morphology. Simulations demonstrate that the model successfully predicts pore migration towards the hottest portion of the fuel, the centerline. The simulations also demonstrate changes in pore shape that are in agreement with previous experimental observations. Initially isotropic pores are ...


Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani May 2017

Characterization Of Plastic Deformation Evolution In Single Crystal And Nanocrystalline Cu During Shock By Atomistic Simulations, Mehrdad Mirzaei Sichani

Theses and Dissertations

The objective of this dissertation is to characterize the evolution of plastic deformation mechanisms in single crystal and nanocrystalline Cu models during shock by atomistic simulations. Molecular dynamics (MD) simulations are performed for a range of particle velocities from 0.5 to 1.7 km/s and initial temperatures of 5, 300 and 600 K for single crystal models as well as particle velocities from 1.5 to 3.4 km/s for nanocrystalline models with grain diameters of 6, 11, 16 and 26 nm. For single crystal models, four different shock directions are selected, <100>, <110>, <111> and <321>, and dislocation density behind ...


Design, Modeling, Fabrication, And Testing Of A Multistage Micro Gas Compressor With Piezoelectric Unimorph Diaphragm And Passive Microvalves For Microcooling Applications, Shawn Thanhson Le Jan 2017

Design, Modeling, Fabrication, And Testing Of A Multistage Micro Gas Compressor With Piezoelectric Unimorph Diaphragm And Passive Microvalves For Microcooling Applications, Shawn Thanhson Le

Doctoral Dissertations

This dissertation investigates the development of a multistage micro gas compressor utilizing multiple pump stages cascaded in series to increase the pressure rise with passive microvalves and piezoelectric unimorph diaphragms. This research was conducted through modeling, simulation, design, and fabrication of the microcompressor and its components. A single-stage and a two-stage microcompressor were developed to demonstrate and compare the performance and effectiveness of using a cascaded multistage design.

Steady fluid flow through static microvalves structure was studied to gain insight on its gas flow dynamics and characteristics. Transient analysis combined with the structure's interaction was investigated with an analytical ...


Carbon Nanotube Thermal Interfaces And Related Applications, Stephen L. Hodson Dec 2016

Carbon Nanotube Thermal Interfaces And Related Applications, Stephen L. Hodson

Open Access Dissertations

The development of thermal interface materials (TIMs) is necessitated by the temperature drop across interfacing materials arising from macro and microscopic irregularities of their surfaces that constricts heat through small contact regions as well as mismatches in their thermal properties. Similar to other types of TIMs, CNT TIMs alleviate the thermal resistance across the interface by thermally bridging two materials together with cylindrical, high-aspect ratio, and nominally vertical conducting elements. Within the community of TIM engineers, the vision driving the development of CNT TIMs was born from measurements that revealed impressively high thermal conductivities of individual CNTs. This vision was ...


Optimal Design Of Sound Absorbing Systems With Microperforated Panels, Nicholas Nakjoo Kim Dec 2016

Optimal Design Of Sound Absorbing Systems With Microperforated Panels, Nicholas Nakjoo Kim

Open Access Dissertations

As the development of technology makes economic prosperity and life more convenient, people now desire a higher quality of life. This quality of life is based not only on the convenience in their life but also on clean and eco-friendly environments. To meet that requirement, much research is being performed in many areas of eco-friendly technology, such as renewable energy, biodegradable content, and batteries for electronic vehicles.

This tendency is also obvious in the acoustics area, where there are continuing attempts to replace fiber-glass sound absorbers with fiber-free materials. The combination of microperfoated panels (MPP) (one of the fiber-free sound ...


Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li Dec 2016

Hydrodynamics Of Swimming Microorganisms In Complex Fluids, Gaojin Li

Open Access Dissertations

Swimming motion of microorganisms, such as spermatozoa, plankton, algae and bacteria, etc., ubiquitously occurs in nature. It affects many biological processes, including reproduction, infection and the marine life ecosystem. The hydrodynamic effects are important in microorganism swimming, their nutrient uptake, fertilization, collective motions and formation of colonies. In nature, microorganisms have evolved to use various fascinating ways for locomotion and transport. Different designs are also developed for the locomotion of artificial nano- and microswimmers. In this study, we use several different computational models to investigate the behavior of microswimmers.

Microorganisms typically swim in the low Reynolds number regime, where inertia ...


Energy Localization And Heat Generation In Composite Energetic Systems Under High-Frequency Mechanical Excitation, Jesus O. Mares Dec 2016

Energy Localization And Heat Generation In Composite Energetic Systems Under High-Frequency Mechanical Excitation, Jesus O. Mares

Open Access Dissertations

In this work, the ability to use high frequency mechanical excitation to generate significant heating within plastic bonded explosives, as well as single energetic particles embedded within a viscoelastic binder, is studied. In this work, the fundamental mechanisms associated with the conversion of high-frequency mechanical excitation to heat as applied to these composite energetic systems are thoroughly investigated.

High-frequency contact excitation has been used to generate a significant amount of heat within samples of PBX 9501 and representative inert mock materials. Surface temperature rises on the order of 10 °C were observed at certain frequencies over a range from 50 ...


Experimentally Validated 3d Md Model For Afm-Based Tip-Based Nanomanufacturing, Rapeepan Promyoo Dec 2016

Experimentally Validated 3d Md Model For Afm-Based Tip-Based Nanomanufacturing, Rapeepan Promyoo

Open Access Dissertations

In order to control AFM-based TBN to produce precise nano-geometry efficiently, there is a need to conduct a more focused study of the effects of different parameters, such as feed, speed, and depth of cut on the process performance and outcome. This is achieved by experimentally validating a MD simulation model of nanomachining, and using it to conduct parametric studies to guide AFM-based TBN. A 3D MD model with a larger domain size was developed and used to gain a unique insight into the nanoindentation and nanoscratching processes such as the effect of tip speed (e.g. effect of tip ...


A Sharp Interface Isogeometric Strategy For Moving Boundary Problems, Tao Song Dec 2016

A Sharp Interface Isogeometric Strategy For Moving Boundary Problems, Tao Song

Open Access Dissertations

The proposed methodology is first utilized to model stationary and propagating cracks. The crack face is enriched with the Heaviside function which captures the displacement discontinuity. Meanwhile, the crack tips are enriched with asymptotic displacement functions to reproduce the tip singularity. The enriching degrees of freedom associated with the crack tips are chosen as stress intensity factors (SIFs) such that these quantities can be directly extracted from the solution without a-posteriori integral calculation.

As a second application, the Stefan problem is modeled with a hybrid function/derivative enriched interface. Since the interface geometry is explicitly defined, normals and curvatures can ...


Fracture Analysis In Biomimetic Bouligand Architectures, Nobphadon Suksanqpanya Dec 2016

Fracture Analysis In Biomimetic Bouligand Architectures, Nobphadon Suksanqpanya

Open Access Dissertations

The Bouligand structure, which is found in many biological materials, is a hierarchical architecture that features uniaxial fiber layers assembled periodically into a helicoidal pattern. Many studies have highlighted the high damage-resistant performance of Bouligand structures and its biomimetic materials. One of the outstanding species with the Bouligand structures is the smashing Mantis Shrimp, Odontodactylus Scyllarus, (or stomatopod) due to its capability of generating high speed, high acceleration blows using its raptorial appendage to defeat highly armored preys. The load-bearing part of this appendage, the dactyl club, contains an interior region, which is mainly characterized by the Bouligand structure. This ...


Optical Sub-Diffraction Limited Focusing For Confined Heating And Lithography, Luis M. Traverso Dec 2016

Optical Sub-Diffraction Limited Focusing For Confined Heating And Lithography, Luis M. Traverso

Open Access Dissertations

Electronics and nanotechnology is constantly demanding a decrease in size of fabricated nanoscale features. This decrease in size has become much more difficult recently due to the limited resolution of optical systems that are fundamental to many nanofabrication methods. A lot of effort has been made to fabricate devices smaller than the diffraction limit of light. Creating devices that are capable of confining fields by means of interference patterns of propagating wave modes and surface plasmon, has proven successful to confine light into smaller spot sizes.

Zone plate diffraction lenses generate spots with dimensions very close to the diffraction limit ...


Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang Dec 2016

Fundamental Studies Of Flame Propagation In Lean-Burn Natural Gas Engines, Zhiyan Wang

Open Access Dissertations

Lean-burn natural gas engines offer enhanced thermal efficiencies and reduced soot and NOx emissions. However, cycle-to-cycle variability in combustion that can result from unreliable ignition, variability in equivalence ratio and quenching is a challenge. Reliability of ignition can be improved by employing a dual-fuel ignition strategy in which a small quantity of diesel fuel is injected to initiate ignition. Computational studies of n-heptane/methane-air mixing layers are performed to provide insight into the fundamental physics of dual-fuel ignition. The results show that the characteristic time required for steady premixed flame propagation has three components: time for autoignition to occur, time ...


Size Scaling Of Strength And Toughness For 3d Printed Polymer Specimens, Darren Thomas Bell Dec 2016

Size Scaling Of Strength And Toughness For 3d Printed Polymer Specimens, Darren Thomas Bell

Open Access Theses

To find material systems that offer low density and high strength, stiffness or toughness, hierarchically designed material systems have provided a promising research area. This thesis lays the groundwork for designing efficient micro-architectured material systems by characterizing size effects for 3d printed polymer parts. Two methods were used to analyze data from 3-point bend tests for specimens of varying size: the load-separation method was used for finding the point of crack growth initiation and Bazant’s method was used to find shape independent strength at failure. The strength values were used as inputs for finding size independent material constants within ...


Passive Thermal Management Using Phase Change Materials, Yash Yogesh Ganatra Dec 2016

Passive Thermal Management Using Phase Change Materials, Yash Yogesh Ganatra

Open Access Theses

The trend of enhanced functionality and reducing thickness of mobile devices has led to a rapid increase in power density and a potential thermal bottleneck since thermal limits of components remain unchanged. Active cooling mechanisms are not feasible due to size, weight and cost constraints. This work explores the feasibility of a passive cooling system based on Phase Change Materials (PCMs) for thermal management of mobile devices. PCMs stabilize temperatures due to the latent heat of phase change thus increasing the operating time of the device before threshold temperatures are exceeded. The primary contribution of this work is the identification ...


Liquid Metal Particle Popping: Nanoscale To Macroscale, Trevor R. Lear Dec 2016

Liquid Metal Particle Popping: Nanoscale To Macroscale, Trevor R. Lear

Open Access Theses

Liquid metal nanoparticles can be used to produce stretchable electronic devices. Understanding the mechanical properties of liquid metal nanoparticles is crucial to optimizing their use in various applications, especially printing of flexible, stretchable electronics. Smaller nanoparticles are desired for high-resolution printing and compatibility with existing scalable manufacturing methods; however, they contain less liquid metal and are more difficult to rupture than larger particles, making them less desirable for post-processing functionality. This study investigates the mechanics of liquid metal particle rupture as a function of particle size. We employ compression of particle films to characterize the composition of the particle core ...


Reaction Tuning Of Selectively Deposited Nano-Thermite Inks For Thrust And Heat Deposition, Raghav Ramachandran Dec 2016

Reaction Tuning Of Selectively Deposited Nano-Thermite Inks For Thrust And Heat Deposition, Raghav Ramachandran

Open Access Theses

Currently there is very little systematic work that quantifies the performance of energetic materials in terms of thrust or heat deposition applied to electronic circuits. A better understanding of the interactions between nano-scale energetic materials and electronic systems, as a function of stoichiometry is needed for enhanced defeat. Both of these needs are addressed in this research. Formulations of Al-CuO and Al-Bi2O3 nano-thermites were prepared at different equivalence ratios and selectively deposited onto silicon substrates and thrust and heat deposition of these materials was quantified. Both nano-thermite systems produced maximum thrust near stoichiometric ratios, and more fuel-rich mixtures led to ...


An Investigation Of Composite Failure Analyses And Damage Evolution In Finite Element Models, Ann M. Frappier Dec 2016

An Investigation Of Composite Failure Analyses And Damage Evolution In Finite Element Models, Ann M. Frappier

Open Access Theses

This paper presents a composite conical structure used commonly in flight-qualification testing. This structure’s overall load-displacement behavioral response is characterized. Mixed-mode multidelamination in a layered composite specimen is considered in Abaqus/Explicit through both the Virtual Crack Closure Technique and Cohesive Elements. The Virtual Crack Closure Technique and Cohesive Elements are compared against experimental test results presented in literature. Further, a thorough comparison in which the effects of failure criteria type, through-thickness mesh density, and finite element type on the progressive failure response of this composite assembly is discussed. Lastly, Abaqus/Standard and Helius PFA are compared in order ...


Thermal Transport In Lithium Ion Batteries: An Experimental Investigation Of Interfaces And Granular Materials, Aalok Jaisheela Uday Gaitonde Dec 2016

Thermal Transport In Lithium Ion Batteries: An Experimental Investigation Of Interfaces And Granular Materials, Aalok Jaisheela Uday Gaitonde

Open Access Theses

Increasing usage and recent accidents due to lithium-ion (Li-ion) batteries exploding or catching on fire has inspired research on the characterization and thermal management of these batteries. In cylindrical 18650 cells, heat generated during the battery's charge/discharge cycle is poorly dissipated to the surrounding through its metallic case due to the poor thermal conductivity of the jelly roll, which is spirally wound with many interfaces between electrodes and the polymeric separator. This work presents a technique to measure the thermal conduction across the metallic case-plastic separator interface, which ultimately limits heat transfer out of the jelly roll.

The ...


In-Situ Particle Sizing Of Agglomerates In Aluminized Solid Composite Propellants Using Digital Inline Holography (Dih), Michael S. Powell Dec 2016

In-Situ Particle Sizing Of Agglomerates In Aluminized Solid Composite Propellants Using Digital Inline Holography (Dih), Michael S. Powell

Open Access Theses

Aluminized ammonium perchlorate composite propellants (APCP) form large molten agglomerated particles that can result in poor combustion performance and increased two-phase flow losses. Quantifying agglomerate size distributions is important for assessing these losses for different types of aluminum fuels that can help improve rocket performance. It is highly desirable to measure particle sizes in-situ using non-intrusive optical methods, rather than conventional particle collection, which can have large uncertainties. Regular high-speed microscopic imaging suffers from a limited depth of field. Digital inline holography (DIH) is an alternative approach that results in 3D information through numerical reconstruction. In this paper, DIH approach ...


Analysis Of Composite Plates By Using Mechanics Of Structure Genome And Comparison With Ansys, Banghua Zhao Dec 2016

Analysis Of Composite Plates By Using Mechanics Of Structure Genome And Comparison With Ansys, Banghua Zhao

Open Access Theses

Motivated by a recently discovered concept, Structure Genome (SG) which is defined as the smallest mathematical building block of a structure, a new approach named Mechanics of Structure Genome (MSG) to model and analyze composite plates is introduced. MSG is implemented in a general-purpose code named SwiftComp™, which provides the constitutive models needed in structural analysis by homogenization and pointwise local fields by dehomogenization. To improve the user friendliness of SwiftComp™, a simple graphic user interface (GUI) based on ANSYS Mechanical APDL platform, called ANSYS-SwiftComp GUI is developed, which provides a convenient way to create some common SG models or ...


Free Edge Stress Analysis Of Laminated Structures With Arbitrary Cross Sections Using Mechanics Of Structure Genome, Lingxuan Zhou Dec 2016

Free Edge Stress Analysis Of Laminated Structures With Arbitrary Cross Sections Using Mechanics Of Structure Genome, Lingxuan Zhou

Open Access Theses

Composite laminates have been increasingly used in advanced structural applications, due to their excellent strength-to-weight properties and considerable flexibility on designing with respect to the laminate layup. However, the heterogeneity and anisotropy of composite laminates have brought many challenges for analysis and numerous researches have been devoted in this field. A well known problem which has been studied intensively is the so-called free-edge problem. It states that due to the mismatch in elastic properties of adjacent layers, full-scale three-dimensional (3D) and highly concentrated stress fields will occur in the vicinity of the free edges. The interlaminar stresses grow very rapidly ...


The Effect Of Process Parameters And Surface Condition On Bond Strength Between Additively Manufactured Components And Polymer Substrates, Bharat Bhushan Chivukula Dec 2016

The Effect Of Process Parameters And Surface Condition On Bond Strength Between Additively Manufactured Components And Polymer Substrates, Bharat Bhushan Chivukula

Theses and Dissertations

Additive patching is a process in which printers with multiple axes deposit molten material onto a pre-defined surface to form a bond. Studying the effect of surface roughness and process parameters selected for printing auxiliary part on the bond helps in improving the strength of the final component. Particularly, the influence of surface roughness, as established by adhesion theory, has not been evaluated in the framework of additive manufacturing (AM). A full factorial design of experiments with five replications was conducted on two levels and three factors, viz., layer thickness, surface roughness, and raster angle to examine the underlying effects ...


Modifying Burning Rate And Agglomeration Size In Aluminized Composite Solid Propellants Using Mechanically Activated Metals, Hatem Mohamed Belal Dec 2016

Modifying Burning Rate And Agglomeration Size In Aluminized Composite Solid Propellants Using Mechanically Activated Metals, Hatem Mohamed Belal

Open Access Dissertations

Agglomeration reduction techniques are important field in solid propellant industry, Large agglomeration results in excessive two phase losses. Tailored composite particles has been applied to tailor aluminum particle ignition and combustion. In this research, mechanical activated aluminum magnesium powders are synthesized, tested in both laser ignition using CO2 and propellant. Prepared powders categorized into particle size that suitable for propellant application. Laser ignition tests showed that the prepared powder are more reactive than magnalium which has the same Al:Mg weight ratio. Agglomeration capturing showed that the prepared powder produce much less than neat aluminum or even similar physical mixture ...


Thermomechanical Properties Of Novel Lanthanum Zirconate Based Thermal Barrier Coatings - An Integrated Experimental And Modeling Study, Xingye Guo Dec 2016

Thermomechanical Properties Of Novel Lanthanum Zirconate Based Thermal Barrier Coatings - An Integrated Experimental And Modeling Study, Xingye Guo

Open Access Dissertations

Thermal barrier coatings (TBCs) are refractory materials deposited on gas turbine components, which provide thermal protection for metallic components at operating conditions. The current state-of-art TBC material is yttria-stabilized zirconia (YSZ), whose service temperature is limited to 1200 celsius, due to sintering and phase transition at higher temperatures. In comparison, lanthanum zirconate (La2Zr2O7, LZ) has become a promising candidate material for TBCs due to its lower thermal conductivity and higher phase stability compared to YSZ.

The primary objective of this thesis is to design a novel robust LZ-based TBC system suitable for applications beyond 1200 celsius. Due to LZ’s ...


Concurrent Detection And Isolation Of Cellular And Molecular Biomarkers, Wanfeng Huang Dec 2016

Concurrent Detection And Isolation Of Cellular And Molecular Biomarkers, Wanfeng Huang

Open Access Dissertations

Detection of cancer markers such as protein biomolecules and cancer cells in bodily fluids is of great importance in early diagnosis, prognosis as well as evaluation of therapy efficacy. Numerous devices have been developed for detecting either cellular or molecular targets, however there has not yet been a system that can simultaneously detect both cellular and molecular targets effectively. Molecule and cell-based assays are important because each type of target can tell a different story about the state of the disease and the two types of information can potentially be combined and/or compared for more accurate biological or clinical ...