Mechanical Engineering Commons^™

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 …

Early Bearing Fault Analysis Using High Frequency Enveloping Techniques, Ilya Shulkin

Open Access Theses

High frequency acceleration enveloping is one of many tools that vibration analysts have at their disposal for the diagnosis of bearing faults in rotating machinery. This technique is believed to facilitate very early detection of potential failures by detecting low amplitude repetitive impacts in frequency ranges above conventional condition monitoring. One traditional enveloping method uses a mathematical operation known as the Hilbert transform along with other signal processing procedures such as band-pass filtering and full-wave rectification. For comparison, another method uses a proprietary algorithm included in National Instruments’ LabVIEWTM add-on package: Sound and Measurement Suite. Enveloping’s inherent problem with noise …

Investigation Of Thin Film Thermal Transport Using Micro-Raman Thermometry And Tip Enhanced Raman Spectroscopy, Mithun Srinivasan

Open Access Theses

In recent years, a steady increase in the need for packing more energy in smaller devices had driven the need for better understanding of thermal transport in thin films and designing methods to manipulate them. This can be attributed as the reason for numerous efforts made in the past decade to achieve temperature resolution at nanoscale. Such techniques can help us in understanding the thermal conductivity of thin films which can result in an improved performance of these devices. The temperature probing technique must be non-invasive to avoid damaging the vulnerable thin films, fast to study the energy transport and …

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 …

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 …

Development, Characterization, & Implementation Of Phase-Change Material Cold Plates For Hybrid-Electric Vehicle Battery Systems, Kevin Cwiok

Doctoral Dissertations and Master's Theses

Due to the regulations on internal combustion engine vehicles, there is a large demand of hybrid and electric vehicles with large battery packs as Energy Storage Systems (ESS) capable of long ranges and decreased emissions. These battery packs output large heat loads during charge-depletion mode and currently require active cooling to keep the batteries within operating conditions. The current systems relied onto achieve this are the air and liquid cooled thermal managements systems. A recent alternative approach to current cooling for ESS thermal management is the use of phase-change materials (PCMs). PCMs regulate the temperature of the ESS by leveraging …

Traction And Launch Control For A Rear-Wheel-Drive Parallel-Series Plug-In Hybrid Electric Vehicle, Adam Michael Szechy

Doctoral Dissertations and Master's Theses

Hybrid vehicles are becoming the future of automobiles leading into the all-electric generation of vehicles. Electric vehicles come with a great increase in torque at lower RPM resulting in the issue of transferring this torque to the ground effectively. In this thesis, a method is presented for limiting wheel slip and targeting the ideal slip ratio for dry asphalt and low friction surfaces at every given time step. A launch control system is developed to further reduce wheel slip on initial acceleration from standstill furthering acceleration rates to sixty miles per hour. A MATLAB Simulink model was built of the …

Best Practices For Volume Flow Rate Measurements Using Piv At The Exit Of A Turbulent Planar Jet, Rick Cressall

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Particle image velocimetry (PIV) is used to make volume-flow-rate measurements at the exit of a turbulent, planar nozzle. The objective of this report is to assess a range of data acquisition and processing parameters. Data is acquired for volume flow rates of Reynolds numbers between 10,000 and 100,000 for both two-component (2C) and stereo PIV. The parameters are systematically changed one at a time and evaluated using differences in uncertainty, calculation time, and volume- flow-rate deviation. Data acquisition parameters follow the trends of previous work. A multitude of processing parameters were varied for several PIV processing methods. Recommendations for each …

Modeling Methods For Merging Computational And Experimental Aerodynamic Pressure Data, Jacob Courtney Haderlie

Open Access Dissertations

This research describes a process to model surface pressure data sets as a function of wing geometry from computational and wind tunnel sources and then merge them into a single predicted value. The described merging process will enable engineers to integrate these data sets with the goal of utilizing the advantages of each data source while overcoming the limitations of both; this provides a single, combined data set to support analysis and design. The main challenge with this process is accurately representing each data source everywhere on the wing. Additionally, this effort demonstrates methods to model wind tunnel pressure data …

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 …

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 assessments. …

A Method For Selecting Hvac Retrofit Solutions For Existing Small- And Medium-Sized Commercial Buildings, Bonggil Jeon

Open Access Dissertations

The primary purpose of the present study is to develop a framework and methodology for evaluating appropriate Heating, Ventilating, and Air Conditioning (HVAC) retrofit solutions that can be effectively retrofitted into different types of small- and medium-sized commercial buildings (SMSCB). Additionally, development of an advanced data-driven decision-making tool is introduced as a benefit of proposed framework. In recent years, considerable attention has been focused on retrofits of existing commercial buildings (IBE, 2013b). In fact, the Commercial Building Energy Consumption Survey (CBECS) 2003 (EIA, 2006) indicates that over 70% of existing commercial buildings across the United States are more than twenty …

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 …

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 …

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 be …

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. …

On The Use Of Mechanical And Acoustical Excitations For Selective Heat Generation In Polymer-Bonded Energetic Materials, Daniel C. Woods

Open Access Dissertations

To address security issues in both military and civilian settings, there is a pressing need for improved explosives detection technologies suitable for trace vapor detection. In light of the strong dependence of vapor pressure on temperature, trace vapor detection capabilities may be enhanced by selectively heating target materials by external excitation. Moreover, polymer-bonded energetic materials may be particularly susceptible to heating by mechanical or acoustical excitation, due to the high levels of damping and low thermal conductivities of most polymers. In this work, the thermomechanical response of polymer-based energetic composites and methods for acoustical excitation are investigated in order to …

Photoelectrochemical And Photophysical Studies Of Carbon Nanotube And Molybdenum Disulfide Based Light Harvesting Devices, Hanyu Zhang

Open Access Dissertations

There is a critical need in utilizing solar radiation as a renewable energy source. While photovoltaic solar cells are widely used, much attention has been devoted in the past decade to developing nanotechnology for potential cost reduction and improved device efficiency and reliability. Low-dimensional materials offer unique physical properties which may be exploited for solar energy harvesting and conversion. Understanding their fundamental properties and developing relevant manufacturing strategies will thus pave the road toward high-performance, cost-effective, light-harvesting devices.

This thesis has investigated single-wall carbon nanotubes (SWCNTs) and molybdenum disulfide (MoS2) nanolayers for their light-harvesting ability in donor-acceptor systems. These materials …

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 to gain confidence …

Uncertainty Quantification On Industrial High Pressure Die Casting Process, Jiahong Fu

Open Access Theses

High pressure die casting (HPDC) is a famous manufacturing technology in industry. This manufacturing process is simulated by commercial code to shed the light on the quality of casting product. The casting product quality might be affected by the uncertainty in the simulation parameter settings. Thus, the uncertainty quantification on HPDC process is significant to improve the casting quality and the manufacturing efficiency.

In this work, three uncertainty quantifications and sensitivity analyses on the A380 aluminum alloy HPDC process of intermediate speed plate are performed. The material thermophysical properties, boundary conditions of the model, and operational as well as artificial …

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

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 …

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 …

Impedance-Resolved Performance And Durability In Redox Flow Batteries, Alan Michael Pezeshki

Doctoral Dissertations

The realization of redox flow batteries (RFBs) as a grid-scale energy solution depends on improving the performance and lifetime of the technology to decrease the high capital costs. The electrodes are a key component in the RFB; performance enhancement is often achieved through chemical or thermal treatments of commercially available porous carbon materials.

This dissertation uses impedance spectroscopy-based methods to gain insight into performance and durability in RFBs, enabling intelligent cell design. Initial work focused on understanding the impact of improved electrode and membrane properties on system performance. An accelerated stress test was then developed that can be used to …

Fundamental Studies Of Electrochemical Reactions And Microfluidics In Proton Exchange Membrane Electrolyzer Cells, Jingke Mo

Doctoral Dissertations

In electrochemical energy devices, including fuel cells, electrolyzers and batteries, the electrochemical reactions occur only on triple phase boundaries (TPBs). The boundaries provide the conductors for electros and protons, the catalysts for electrochemical reactions and the effective pathways for transport of reactants and products. The interfaces have a critical impact on the overall performance and cost of the devices in which they are incorporated, and therefore could be a key feature to optimize in order to turn a prototype into a commercially viable product. For electrolysis of water, proton exchange membrane electrolyzer cells (PEMECs) have several advantages compared to other …

Investigation Of Localized Performance And Gas Evolution In All-Vanadium Redox Flow Batteries Via In-Situ Distributed Diagnostic Techniques, Jason Thomas Clement

Doctoral Dissertations

All-vanadium redox flow batteries (VRFBs) are an emerging grid-scale energy storage technology; however, enhancements in terms of performance, efficiency, durability, and cost are required before it can become commercially viable. These improvements are achievable through the development of advanced materials, superior architecture, and ultimately a deeper fundamental understanding of the influence of various phenomena and operational parameters on cell performance. There currently are a lack of in-situ experimental diagnostic techniques which can help in achieving this fundamental understanding.

Two separate distributed diagnostic techniques were developed in this work: in-plane current distribution, and neutron radiography. Localized current distribution measurements can identify …

Parametric Instability And Vibration Suppression Of Planetary Gear Transmissions Supported On Boundary Struts, Peng Guan

Doctoral Dissertations

This dissertation explores the effects of discrete boundary strut properties on stability and vibration of the planetary gear transmission (PGT) driveline systems. Also, a robust output feedback control law is developed to actively control the PGT system vibrations. To better obtain boundary strut properties, a light-weight boundary strut design was developed for two popular boundary strut configurations by considering yield stress, buckling, and local buckling constraints. To facilitate analysis and development of the active control law, a comprehensive analytical PGT driveline system with elastic ring model, including gyroscopic effect and rotating-frame damping, is developed. The equation of motion of the …

Turbine Engine Rotor Blade Damage Detection Through The Analysis Of Vibration Of Stationary Components, Jon Rylan Cox

Doctoral Dissertations

Rotor blade fault detection and health monitoring systems are crucial for gas turbine engine testing and evaluation. The most commonly used techniques involve monitoring blades directly using strain gages, or drilling optical access holes in the engine casing for non-contact probes to monitor blade deflection and vibration. In this work, less intrusive, indirect techniques for rotor blade fault detection are developed, based on the hypotheses that the vibratory response of stationary components excited by the rotor blade dynamic pressure pulse can be used to detect the presence, location, and severity of rotor blade damage and changes in rotor blade natural …

Experimental Investigation Of Chicken Manure Pyrolysis And Gasification, Mohamed Hussein Hussein

Theses and Dissertations

The dependency on renewable resources of energy in power production is a necessary step that mankind has to take if we want our advances in life and technology to resume. In a century or two, fossil fuels will be depleted, and if we do not start to take action, Energy will be the most expensive and rare item on our planet. Biomass is one of the sources of renewable energy with an advantage of being the closest in characteristics to fossil fuels. The evolved gases are similar to fossil fuel gases which makes itthe easiest source to switch to, with …

Nanoscale Solutions To Tailor Fiber Architectures For Realizing Composites With Triumvirate Properties, Vishnu Priya Ramineni

All Theses

The paramount need for the development of multifunctional, smart and adaptive material systems for application in industries like automobile, aeronautical and aerospace is undeniable. Polymer composites are fast becoming the primary material options to this demand in light of their superior mechanical properties, low density, high corrosion resistance and easy manufacturability. The design flexibility offered in terms of achieving higher specific properties and light weighting is the key reason behind their success. Among all the properties that composites possess, it is the stiffness, strength and toughness that most applications mandate. These properties however, provide complimentary and contrasting characteristics for composites …