Advanced Materials Characterization Based On Full Field Deformation Measurements,
2013
University of Texas at Arlington
Advanced Materials Characterization Based On Full Field Deformation Measurements, A Paige Carpentier
Mechanical and Aerospace Engineering Dissertations - Archive
Accurate stress-strain constitutive properties are essential for understanding the complex deformation and failure mechanisms for materials with highly anisotropic mechanical properties. Among such materials, glass-fiber- and carbon-fiber-reinforced polymer-matrix composites play a critical role in advanced structural designs. The large number of different methods and specimen types currently required to generate three-dimensional allowables for structural design slows down the material characterization. Also, some of the material constitutive properties are never measured due to the prohibitive cost of the specimens needed. This work shows that simple short-beam shear (SBS) specimens are well-suited for measurement of multiple constitutive properties for composite materials and …
Multi-Objective Design Optimization Of Beol/Fbeol Region During Chip Attachment To Substrate,
2013
University of Texas at Arlington
Multi-Objective Design Optimization Of Beol/Fbeol Region During Chip Attachment To Substrate, Hardik Parekh
Mechanical and Aerospace Engineering Theses - Archive
Semiconductor industry has recognized the need to replace traditional Al/SiO2 interconnects with Cu/Low-k interconnects in the mainstream electronics devices following the latter's impact on power, RC delay, and cross-talk reduction. However due to lower elastic modulus, strength, and poor adhesion characteristic, reliability of the Cu/Low-k interconnects turns out to be a concern for its integration in the back-end-of-line (BEoL). Flip-chip attachment process (cooling from ~200C to room) can result in critical damage in nano-scale Cu/Low-k interconnects. The objective of this study is to improve the reliability of Cu/Low-k interconnects during die attach reflow process for a specific die to substrate …
Design And Control Of A Smart Bed For Pressure Ulcer Prevention,
2013
University of Texas at Arlington
Design And Control Of A Smart Bed For Pressure Ulcer Prevention, Zachary Govier Brush
Mechanical and Aerospace Engineering Theses - Archive
This work details the design, simulation, and experimental testing of a mechanically actuated smart hospital bed for the prevention of pressure ulcers in hospital patients. The smart hospital bed, or Smartbed, is designed to improve the “turning” process currently performed by health care workers, ensuring that patients are turned consistently and decreasing the labor requirement for caregivers. The mechanical structure of the bed is described, along with its advantages over current Smartbed products. Next, dynamic models of the Smartbed actuating systems are discussed along with descriptions of the devised single-unit and overall bed control systems. The control equations determined in …
Design And Evaluation Of A Chemical Reactor For The Pyrolysis Wood Pellets,
2013
University of Texas at Arlington
Design And Evaluation Of A Chemical Reactor For The Pyrolysis Wood Pellets, Pawarat Bootpakdeetam
Mechanical and Aerospace Engineering Theses - Archive
Currently there is interest in converting waste biomass into valuable products, such as fuels and specialty chemicals. However, the product composition, yield, the energy required to run the reaction, and the required residence time are all factors influence the economics of the process. Estimate of these factors at the laboratory scale is important for evaluating whether a pilot or demonstration scale study is warranted. In this work, a bench-scale chemical reactor was designed and constructed to conduct the batch pyrolysis of pelletized biomass. The reactor was tested using pine wood pellets as the feedstock. The feedstock weight to reactor volume …
Optimal Design Of Beams,
2013
University of Texas at Arlington
Optimal Design Of Beams, Shivakumar Samala
Mechanical and Aerospace Engineering Theses - Archive
Beams are basic structural components that are capable of withstanding load primarily by resisting bending. Unlike Euler-Bernoulli beams, Timoshenko beams undergo both shear deformation and rotational effects, making it suitable for analyzing the behavior of thick or short beams, composite beams and beams that are subjected to high frequency excitation when their wave length becomes shorter. This thesis work focuses on optimal design of straight and tapered Timoshenko beams under static and dynamic constraints for rectangular and circular cross sections. In this work Timoshenko beam static and dynamic equations were studied. The finite element method was used for static and …
Study Of The Capabilities Of Electrowetting On Dielectric Digital Microfluidics (Ewod Dmf) Towards The High Efficient Thin-Film Evaporative Cooling Platform,
2013
University of Texas at Arlington
Study Of The Capabilities Of Electrowetting On Dielectric Digital Microfluidics (Ewod Dmf) Towards The High Efficient Thin-Film Evaporative Cooling Platform, Jagath B. Yaddessalage
Mechanical and Aerospace Engineering Dissertations - Archive
With the current technological advancement, the size of the electronic components is being reduced to smaller and compact sizes. In the meantime, the packaging density and power consumption is ever increasing. To tackle this challenge, an efficient cooling technology is required.Thin-film evaporation is a very efficient cooling technology. A practical application using thin-film evaporation is a spray cooling which is known as the cooling method that can handle very high heat flux. However, a random spray of coolant cannot guarantee a thin coolant film, therefore either local dry-out or flooding may occur, which hampers cooling efficiency significantly. Moreover, bulky spraying …
Airdata Sensor Based Position Estimation And Fault Diagnosis In Aerial Refueling,
2013
University of Texas at Arlington
Airdata Sensor Based Position Estimation And Fault Diagnosis In Aerial Refueling, Hakki Erhan Sevil
Mechanical and Aerospace Engineering Dissertations - Archive
Aerial refueling is the process of transferring fuel from one aircraft (the tanker) to another (the receiver) during flight. In aerial refueling operations, the receiver aircraft is exposed to nonuniform wind field induced by tanker aircraft, and this nonuniform wind field leads to differences in readings of airdata sensors placed at different locations on the receiver aircraft. There are advantages and disadvantages of this phenomenon. As an advantage, it is used as a mechanism to estimate relative position of the receiver aircraft inside the nonuniform wind field behind the tanker. Using the difference in the measurements from multiple identical sensors, …
A Semi-Analytical Approach To Obtain Physical Fields In Heterogeneous Materials,
2013
University of Texas at Arlington
A Semi-Analytical Approach To Obtain Physical Fields In Heterogeneous Materials, Thanuuj S. Pathapallli
Mechanical and Aerospace Engineering Dissertations - Archive
Predicting the macroscopic response of heterogeneous materials has been the subject of extensive research in the engineering community, even more so, in the composites guild. With analytical solutions being almost impossible to obtain for such open ended problems, and numerical techniques being computationally expensive, semi-analytical methods are highly sought after. This dissertation is one such effort aimed at presenting a semi-analytical approach that serves as a confluence of effective analytical and numerical techniques, to solve for engineering fields in a heterogeneous material characterized by inclusions embedded in a matrix medium. The approach essentially involves the analytical derivation of permissible functions, …
Thermo-Mechanical Analysis Of Nano-Imprint Lithography,
2013
University of Texas at Arlington
Thermo-Mechanical Analysis Of Nano-Imprint Lithography, Bhavik C. Patel
Mechanical and Aerospace Engineering Theses - Archive
Nanoimprint Lithography is being explored by the semiconductor industries for future high volume fabrication of silicon chips, memory devices and patterned media. Nanolithography and Microlithography has played pivotal role in the field of manufacturing microchips and integrated circuits in semiconductor devices. There is an urge to investigate Nanoimprint lithography, a high-throughput, low-cost and nonconventional lithographic method. Thermal management is a critical area that is necessary to be administrated. As recent advancements are being observed in the field of electronic packaging for thermal optimization, likewise steps are also important in this fabrication process. This process involves a heat that is generated …
Compressibility Effects On The Non-Linear Receptivity Of Boundary Layers To Dielectric Barrier Discharges,
2013
University of Texas at Arlington
Compressibility Effects On The Non-Linear Receptivity Of Boundary Layers To Dielectric Barrier Discharges, Marie F.C. Denison
Mechanical and Aerospace Engineering Theses - Archive
The reduction of drag and aerodynamic heating caused by boundary layer transition is of central interest for the development of hypersonic vehicles. Receptivity to flow perturbation in the form of Tollmien-Schlichting (TS) wave growth often determines the first stage of the transition process, which can be delayed by depositing specific excitations into the boundary layer. Weakly ionized Dielectric Barrier Discharge (DBD) actuators are being investigated as possible sources of such excitations, but little is known today about their interaction with high-speed flows. In this framework, the first part of the thesis is dedicated to a receptivity study of laminar compressible …
Rotordynamic Performance Of A Rotor Supported By Three Pad Hybird Foil Bearings With Controlled Air Injection,
2013
University of Texas at Arlington
Rotordynamic Performance Of A Rotor Supported By Three Pad Hybird Foil Bearings With Controlled Air Injection, Sandesh Gudemane
Mechanical and Aerospace Engineering Theses - Archive
Air Foil Bearings have found their place in the commercial applications of turbo machinery. They are cleaner and more reliable at high speeds than their conventional counterparts (Rolling Element Bearings). Low drag friction and apparently no contact during the operation results in a better service life and superior rotor-dynamic performance of the air foil bearings (AFBs). With these advantages AFB has proved to be a suitable option for oil-free turbo-machinery. Further development in AFBs suggest that pressurizing these bearings externally results in remarkably better load carrying capacity, heat dissipation and a more stable rotor. These externally air pressurized bearings which …
Improving Cooling Efficiency Of Servers By Replacing Smaller Chassis Enclosed Fans With Larger Rack-Mount Fans,
2013
University of Texas at Arlington
Improving Cooling Efficiency Of Servers By Replacing Smaller Chassis Enclosed Fans With Larger Rack-Mount Fans, Bharath Nagendran
Mechanical and Aerospace Engineering Theses - Archive
As a common practice in the data center industry, chassis fans are used to direct air flow independent from neighboring servers. However, these fans are less efficient compared to larger rack level counterparts and also operate at higher sound levels. In this study, a novel approach is proposed whereby the smaller chassis enclosed fans are replaced with an array of larger fans, installed behind the stacked servers that share air flow. As a baseline study for comparison of the current scenario, a CPU dominated 1.5U Open Compute server, with four 60mm fans installed within the server, is characterized experimentally for …
Comparative Analysis Of Widely Used Air Containment Systems In Commercial Data Centers For Maximum Cooling Performance,
2013
University of Texas at Arlington
Comparative Analysis Of Widely Used Air Containment Systems In Commercial Data Centers For Maximum Cooling Performance, Kasturi Rangan Rajagopalan
Mechanical and Aerospace Engineering Theses - Archive
Many data centers implement containment systems to improve cooling system performance. Literature review shows that Hot Aisle Containment System (HACS) have higher supply air temperature set point than Cold Aisle Containment Systems (CACS) [1]. CACS in data centers have claims to support higher density loads when compared to HACS systems [2]. Data center owners suggest that containment of a group of racks can be a very effective technique to improve cooling performance. On the other hand, others suggest that fewer area for containment is better than no containment in data centers that favours the partially contained architectures of HACS and …
Real Time Temperature Prediction In A Data Center Environment Using An Adaptive Algorithm,
2013
University of Texas at Arlington
Real Time Temperature Prediction In A Data Center Environment Using An Adaptive Algorithm, Vishok Amar Kumar
Mechanical and Aerospace Engineering Theses - Archive
Most organizations around the world rely on information systems to run their operations. Data centers are hence a crucial aspect of most organizational operations to ensure business continuity. Disruption in the working of a system can impair the business largely and hence optimizing the environment in which the servers and storage devises of a data center are housed becomes extremely challenging. Most industries design the data center infrastructure to handle peak load conditions thus ensuring a continual functionality of its hosted environment. However, the cost of maintaining such a system is very high. This gives rise to the need of …
A Computational Model To Characterize Different Flow Regimes For Microscale Re-Entry Satellites,
2013
University of Texas at Arlington
A Computational Model To Characterize Different Flow Regimes For Microscale Re-Entry Satellites, Sudharsan Thiruvenkadam
Mechanical and Aerospace Engineering Theses - Archive
Atmospheric re-entry vehicles experience different flow regimes during flight due to the change in atmospheric density along the re-entry trajectory. This change in density creates non-equilibrium regions on the order of mean free path, called Knudsen layer. In the design of atmospheric re-entry vehicles, the flux variations near the wall of the re-entry vehicles are of critical importance. Traditional CFD simulations that use Navier-Stokes equations fail to predict the flow in the Knudsen layer. The Direct Simulation Monte Carlo (DSMC) method is accurate for all flow regimes, and correctly models the Knudsen layer but is computationally expensive. The computational cost …
Materials Selection And Processing Techniques For Small Spacecraft Solar Cell Arrays,
2013
University of Kentucky
Materials Selection And Processing Techniques For Small Spacecraft Solar Cell Arrays, Naseem M. Torabi
Theses and Dissertations--Electrical and Computer Engineering
Body mounted germanium substrate solar cell arrays form the faces of many small satellite designs to provide the primary power source on orbit. High efficiency solar cells are made affordable for university satellite programs as triangular devices trimmed from wafer scale solar cells. The smaller cells allow array designs to pack tightly around antenna mounts and payload instruments, giving the board design flexibility. One objective of this work is to investigate the reliability of solar cells attached to FR-4 printed circuit boards. FR-4 circuit boards have significantly higher thermal expansion coefficients and lower thermal conductivities than germanium. This thermal expansion …
Efficient Uncertainty Quantification In Aerospace Analysis And Design,
2013
Missouri University of Science and Technology
Efficient Uncertainty Quantification In Aerospace Analysis And Design, Yi Zhang
Doctoral Dissertations
"The main purpose of this study is to apply a computationally efficient uncertainty quantification approach, Non-Intrusive Polynomial Chaos (NIPC) based stochastic expansions, to robust aerospace analysis and design under mixed (aleatory and epistemic) uncertainties and demonstrate this technique on model problems and robust aerodynamic optimization. The proposed optimization approach utilizes stochastic response surfaces obtained with NIPC methods to approximate the objective function and the constraints in the optimization formulation. The objective function includes the stochastic measures which are minimized simultaneously to ensure the robustness of the final design to both aleatory and epistemic uncertainties. For model problems with mixed uncertainties, …
Trajectory Generation For Stair Ascent Walking Using Rayleigh Oscillator,
2013
University of Arkansas at Little Rock
Trajectory Generation For Stair Ascent Walking Using Rayleigh Oscillator, T. Afzal, Andrew B. Wright, Kamran Iqbal
Journal of the Arkansas Academy of Science
This paper describes a trajectory generation technique for stair-ascent walking. The knee, hip and ankle joint trajectory during stair ascent are generated using mutually coupled, nonlinear oscillators. The parameters of the oscillators are tuned using the harmonic balance method, which converts the nonlinear differential equations to a set of algebraic equations. Fourier analysis of data generated by stair-ascent walking is performed to extract the amplitude and the phase of the dominant frequency components for each joint trajectory. The solution for the oscillator is assumed to be a sinusoidal wave and then by harmonic balance method the parameters of the oscillator …
The Effect Of Sensor Mass, Sensor Location, And Delamination Location Of Different Composite Structures Under Dynamic Loading,
2013
California Polytechnic State University, San Luis Obispo
The Effect Of Sensor Mass, Sensor Location, And Delamination Location Of Different Composite Structures Under Dynamic Loading, Albert Darien Liu
Master's Theses
This study investigated the effect of sensor mass, sensor location, and delamination location of different composite structures under dynamic loading. The study pertains to research of the use of accelerometers and dynamic response as a cost-effective and reliable method of structural health monitoring in composite structures. The composite structures in this research included carbon fiber plates, carbon fiber-foam sandwich panels, and carbon-fiber honeycomb sandwich panels. The composite structures were manufactured with the use of a Tetrahedron MTP-8 heat press. All work was conducted in the Cal Poly Aerospace Structures/Composites Laboratory. Initial delaminations were placed at several locations along the specimen, …
Elastic–Plastic Analysis And Strength Evaluation Of Adhesive
Joints In Wind Turbine Blades,
2013
University of Nebraska–Lincoln
Elastic–Plastic Analysis And Strength Evaluation Of Adhesive Joints In Wind Turbine Blades, Yi Hua, Ananth Ram Mahanth Kasavajhala, Linxia Gu
Department of Mechanical and Materials Engineering: Faculty Publications
The objective of this paper is to investigate the performance of adhesive joints of carbon/epoxy wind turbine blade subjected to combined bending and tension loadings through finite element method. The influence of adhesive material properties and geometrical details including fillet and imperfections was examined in terms of interlaminar stresses in the adhesive layer. The variation of stress intensity with change in adhesive shear modulus has also been investigated, while contour integral method was used for evaluating the stress intensity factors (SIF) at the imperfection tip. Furthermore, the strength of the joint was assessed through the crack initiation and propagation analysis. …
