Mechanical Engineering Commons^™

Airfoil-Shaped Extension-Twist-Coupled Composite Star-Beams For Rotor Blade Tip Applications, Sthanu Mahadev

Mechanical and Aerospace Engineering Theses - Archive

Rotorcraft blade tips provide the most effective region for aerodynamic control. Rotor blade airloads are proportional to dynamic pressure and as a consequence are typically the highest in the distal blade tip region. Therefore, blade control using aerodynamic forces and moments is most effectively accomplished over the distal region of the blade. Composite materials represent the preferred material option for modern rotor blade design, especially in the field of rotorcraft and wind energy, due to superior strength-to-weight ratio, fatigue resistance and their ability to be easily tailored to incorporate different coupling (bend-twist, extension-twist, etc.) among elastic modes of deformation within …

Design Optimization Using Augmented Lagrangian Particle Swarm Optimization, Chethan Shivappa Thenehalli

Mechanical and Aerospace Engineering Theses - Archive

Engineering optimization problems normally include multiple, non-trivial, non-linear constraints. Traditionally gradient based optimization methods were used to solve these types of problems because of their high computational efficiency. But they generally require continuity of the optimization problem and the computation of derivatives and tend to get trapped in local minima. Hence non gradient based, evolutionary algorithms (EA) which are based on heuristic and stochastic nature and do not require continuity of the design space of the optimization problem and increase the probability to find a global optimal solution, therefore are becoming a popular choice in recent years. This work uses …

Stress Analysis For A Three Phase Plate With A Concentric Circular Inclusion By Deriving An Airy Stress Function, Abhishek Kunchala

Mechanical and Aerospace Engineering Theses - Archive

This thesis derives the Airy stress function for a three phase plate that consists of two concentric circular inclusions and a matrix phase. It incorporates the elastic property of each phase as well as the geometry of the inclusions. An Airy stress function has been derived that satisfies the continuity conditions of the displacement and traction across the phase interface precisely. The obtained results are new and could not have been possible without a computer algebra system (Mathematica).

Finite Element Based Stability Constrained Weight Minimization Of Sandwich Composite Ducts For Airship Applications, Urmi B. Khode

Mechanical and Aerospace Engineering Theses - Archive

High Altitude Long Endurance (HALE) airships are platform of interest due to their persistent observation and persistent communication capabilities. A novel HALE airship design configuration incorporates a composite sandwich propulsive hull duct between the front and the back of the hull for significant drag reduction via blown wake effects. The sandwich composite shell duct is subjected to hull pressure on its outer walls and flow suction on its inner walls which result in in-plane wall compressive stress, which may cause duct buckling. An approach based upon finite element stability analysis combined with a ply layup and foam thickness determination weight …

Preliminary Design Of Mesoscale Turbocompressor And Rotordynamics Tests Of Rotor Bearing System, Md Saddam Hossain

Mechanical and Aerospace Engineering Theses - Archive

A mesoscale turbocompressor spinning above 500,000 RPM is evolutionary technology for micro turbochargers, turbo blowers, turbo compressors, micro-gas turbines, auxiliary power units, etc for automotive, aerospace, and fuel cell industries. Objectives of this work are:1) to evaluate different air foil bearings designed for the intended applications, and 2) to design & perform CFD analysis of a micro-compressor. CFD analysis of shrouded 3-D micro compressor was conducted using Ansys Bladegen as blade generation tool, ICEM CFD as mesh generation tool, and CFS as main solver for different design and off design cases and also for different number of blades. Comprehensive experimental …

Adaptation Of Digital Datcom Into A Conceptual Design Process, Brandon Watters

Mechanical and Aerospace Engineering Theses - Archive

As implied with open-ended `design decision-making' there are multiple prospective conventional and unconventional aircraft solution concepts able to satisfy a given mission specification. The task of defining, assessing and selecting prospective options for the mission at hand is the primary purpose of the aircraft conceptual design (CD) phase. In addition, conceptual design tends to be fast paced and an iterative process structure that requires a quick design-response. This leads the aircraft designer to simplified analysis techniques that focus on the impact (trends and sensitivities) of a new technology on the design. Correctly predicting these trends and sensitivities can be difficult. …

Vehicle Suspension Optimization For Stochastic Inputs, Kailas Vijay Inamdar

Mechanical and Aerospace Engineering Theses - Archive

In the present thesis, a simulation based numerical method has been proposed for optimization of vehicle suspension system for stochastic inputs from random road surface profiles. Road surfaces are classified in based upon the power spectral density functions. The road surface is considered as a stationary stochastic process in time domain assuming constant vehicle speed. Using Fourier transforms, it is possible to generate the road surface elevations as a function of time. Time domain responses of the output of the suspension system are obtained using transfer function techniques. Optimum values of the damper constant are computed by simulation of the …

Feasibility Study Of T700 Rotorcraft Engine Rotor Supported By Hybrid Air Foil Bearings, Mahesh Kumar Varrey

Mechanical and Aerospace Engineering Theses - Archive

A potential solution towards light weighted and simple structured turbomachinery lies in elimination of oil-lubrication system. These promising benefits of oil-free turbomachinery have demanded extensive research in the field of small turbomachinery, leading to the development of different types of oil free bearings. Air foil bearings (AFBs) are one of the oil-free bearings with many advantages over others. AFBs have simple construction, greater service life and reduced maintenance. Their superior dynamic performance compared to traditional rigid surface bearings is an added advantage. Implementation of these foil bearings in the rotorcraft propulsion system decreases the total weight of the engine setup, …

Analysis Of Laminated Tubular Structure Under Torsion, Thana Chomtid

Mechanical and Aerospace Engineering Theses - Archive

Laminated composite shells in particular are prominent in bearing various types of loads and are hence used in many engineering structures. The analysis of laminated composites is quite complicated since the material behavior is anisotropic, which gets further intensified in the analysis of complex structures like tubular structures. Finite element method is a useful method for evaluating and conducting the behavior of thin laminated tubular structure subjected to torsion. In this study, the behavior of shear stress versus angle along the laminated tubular structure cross section was conducted in varies radius ratio which are 1, 0.8, 0.6, 0.4, and 0.2 …

Static And Dynamic Calibration Of A Multi-Component Sidewall Force Balance For A Transonic Ludwieg Tube Wind Tunnel, Michael Gerard Werling

Mechanical and Aerospace Engineering Theses - Archive

Experimentation involving transonic flow requires replicating not only the Mach number but also the Reynolds number. Improper matching of the Reynolds number affects the interaction between the shocks and boundary layer on the surface of an airfoil, moving the position of the shock and altering the downstream flow field. Both Mach and Reynolds numbers have a large influence on the lift and drag characteristics of airfoils, amongst other aerodynamic effects, within the transonic regime of flight. A strain-based, multi-component, sidewall force balance was purchased in 1989 specifically for the transonic Ludwieg tunnel at the University of Texas-Arlington, but proper calibration …

Evaporative Cooling Performance Of A Brazed Microporous Coating On An Aluminum Surface, Ryan M. King

Mechanical and Aerospace Engineering Theses - Archive

The effect of an aluminum microporous coating on evaporative cooling performance was studied using distilled water as the working fluid. The aluminum microporous coating was fabricated by brazing aluminum particles to an aluminum substrate. Microporous coating thicknesses of 175 µm ± 20 µm, 270 µm ± 20 µm, and 900 µm ± 90 µm, and average aluminum particle sizes of 27 µm, 70 µm and 114 µm were used in a parametric study to determine the optimum aluminum microporous coating. A hot water treatment maximized the wickability of the microporous coating. Wickability was measured by vertical dipping of the coating. …

Algebraic Solution To The Planar Rigid Body Impact Problem, Drew Morgan

Mechanical and Aerospace Engineering Theses - Archive

For systems of rigid bodies that undergo impacts, a series of closed-form equations are developed to solve for post-impact velocities which simulate a real-world (energy-consistent) interaction. The analysis is based in the impulse domain, and requires that the surface interaction be characterizable by Coulomb friction and an energetic coefficient of restitution. No iteration, optimization, or numerical methods are used.

Performance Optimization Of Multi-Core Processors Using Core Hopping - Thermal And Structural, Sunil Lingampalli

Mechanical and Aerospace Engineering Theses - Archive

As the work load on the single core processor increases, it's processing speed increases resulting in increased power densities and die temperatures. The increase in die temperature results in decreased performance and reliability and increased leakage currents and cooling costs. In order to decrease the work load and the cooling cost on the single core processor, multi-core processors have been implemented. Multicore Processors also known as Chip Multi Processors (CMP's) are the processors which contain two or more independent cores on a chip. In CMPs, if one core reaches its critical temperature, the workload is transferred to the other. This …

Estimation Of Aircraft States And Wind Exposure In Aerial Refueling, Je Hyeon Lee

Mechanical and Aerospace Engineering Dissertations - Archive

When a tanker and receiver aircraft fly in tight formation in an aerial refueling operation, they are exposed to various sources of wind with varying magnitude and direction. The tanker and the receiver aircraft experience prevailing wind and turbulence. The receiver aircraft is also subject to an additional wind field induced by the wake of the tanker.The receiver aircraft is required to fly in a precise trajectory relative to the tanker. Especially, the receiver aircraft should stay at a position with small tolerances for the fuel transfer operation while the tanker aircraft flies straight level and makes constant altitude turns. …

Atomic Friction Studied By Modeling The Buried Inteface, Yalin Dong, Ashlie Martini, Qunyang Li, Robert W. Carpick

Mechanical Engineering Faculty Research

Molecular dynamics simulation is carried out to model the single-asperity friction in atomic force microscope experiments. Superlubricity is achieved through misalignment between the AFM tip and substrate. Direct observation of the buried interface reveals that incommensurability-induced inhomogeneous shear stress can cause ultra-low atomic scale friction.

A New Look At Optimum Design For Convecting-Radiating Annular Fins Of Trapezoidal Profile, Benjamin T.F. Chung

Mechanical Engineering Faculty Research

This paper deals with a controversial problem in answering the question “Does the optimum fin design always exist? If not, what are the optimization ranges and limitations?” These authors employ a general example of convecting-radiating trapezoidal annular fin with heat transfer at the tip and wall resistance at the interface. The present results indicate that the answer to the above first question is negative. The ranges of fin optimum design under different thermal and physical conditions are proposed. The effects of Biot number, radiation number, the heat loss at the tip, fin profile and overall wall resistance on fin optimization …

Fabrication Of Micropatterns On 3d Surfaces And Generation Of Linked Zno Nanowires, Hui Wang

Mechanical and Aerospace Engineering Dissertations - Archive

Conventional lithographic approaches are good at fabricating structures on the top surfaces of substrates. They are not suited for 3D surface patterning due to the fact that vertical radiation exposure is employed to transfer patterns. In the meanwhile, patterns generated on 3D surfaces, such as the vertical sidewalls of silicon channels and the irregular surfaces of glass micropipettes may provide valuable applications in microfluidics, 3D circuits, bioengineering and so on. In this work, we developed new approaches to produce metal micropatterns on the vertical sidewalls of silicon channels as well as to fabricate two separated metal microlines on the tips …

Development Of An Experimental And Analytical Model Of An Active Cooling Method For High-Power Three-Dimensional Integrated Circuit (3d-Ic) Utilizing A Multidimensional Configured Thermoelectric Modules, Huy Phan

Mechanical and Aerospace Engineering Dissertations - Archive

An increase in demand for more functionality and capacity of microelectronic components within the same logistic footprint drives the growth of three-dimensional integrated circuit (3D-IC) packaging technologies in recent years. However, the reduction in size and an increase in transistors density also intensified the heat flux of stacked-dice, which introduces many thermal challenges at both the package and cooling levels. Traditional passive cooling system such as forced air convection cooling, phase change materials and passive or active heat sinks will become inadequate to cool future processors and cannot accommodate the demand of future sub-ambient cooling of 3D-ICs. Within the past …

Hybrid Dynamic Simulation For Performance Optimization Of Legged Mechanisms, Daniel Montrallo Flickinger

Mechanical and Aerospace Engineering Dissertations - Archive

Agile locomotion is needed for mobile robots to efficiently navigate challenging terrain. The ability of an agile legged mobile robot to abruptly change trajectory allows it toquickly react to obstacles and successfully operate in environments usually more suited forlegged animals. The research presented herein aims to increase the agility and performanceof legged robots.Using hybrid dynamic simulation, novel methods are developed to model the inter-action of a legged robot with the ground. In considering robot agility, an accurate model ofthe events that occur while in contact is needed. Methods are developed to model groundinteraction where oblique angled impacts occur, and to …

Design And Modeling Techniques For Cooling Of Telecommunication Systems, Naveen Kannan

Mechanical and Aerospace Engineering Theses - Archive

Conventional data centers are extremely large buildings that have complex power distribution and cooling systems. These traditional brick and mortar data centers employ relatively expensive cooling systems and are inefficient. It has in turn led to an increase in construction and operational costs. These inefficiencies of traditional data centers can be overcome by partitioning the server load into modular sections which can be deployed, powered and cooled depending on availability and requirement. Furthermore, improvements in efficiency and operational costs can be achieved by employing "free cooling" to cool the IT equipment. Free cooling involves the introduction of outside air through …

Design Optimization Of A Wind Turbine Blade, Bharath Koratagere Srinivasa Raju

Mechanical and Aerospace Engineering Theses - Archive

This work focuses on designing a blade of 45 meters in length that produces a power of 1.6 MW. The design of the blade was done using the Blade Element Momentum theory and the Prandtl's tip loss factor was used. The aerodynamic loads and differential power at are tabulated and plotted.The finite element method for analysis of the blade is used. As the chord lengths vary decreasingly along the blade radii in order to use the simple beam theory the breath and height of the blade is considered as a function of the chord length, hence the analysis is done …

Filling Of Methane/Air Mixture In A Tube For Pulse Detonation Engines, Shravani Dwarakapally

Mechanical and Aerospace Engineering Theses - Archive

In pulse detonation engines, filling is a time consuming process; reducing these times will help to increase the frequency. The filling of a detonation tube, 1 m long tube with an internal diameter of 101.6 mm, closed at one end and opened at the other, was studied using the unsteady flow solver methane and air nominally at STP· Three cases were examined: (i) a 25.4 mm diameter port at the center of the closed end, (ii) nine ports of 25.4 mm diameter, one at the center of the closed end and eight distributed in two diametrically opposite rows, equally, four …

Control Of Airship Motion In The Presence Of Wind, Jatuporn Nakpiam

Mechanical and Aerospace Engineering Theses - Archive

This research effort develops a guidance and control system for a small airship to fly through assigned waypoints in the three dimensional space with a desired speed in the presence of wind and wind gust. In the control system development and validation, a simulation environment based on the nonlinear 6-DOF model of an airship, including the effect of the wind, is used. The airship has five control variables, the main thrust, the main thrust angle, the tail thrust, elevator and rudder deflections. The effectiveness of the elevator and rudder degrades as the speed of the airship decreases. The controller design …

Multi-Sensor Optimization Of The Simultaneous Turning And Boring Operation, Erick Johan Deane

Electronic Theses and Dissertations

To remain competitive in today’s demanding economy, there is an increasing demand for improved productivity and scrap reduction in manufacturing. Traditional manufacturing metal removal processes such as turning and boring are still one of the most used techniques for fabricating metal products. Although the essential metal removal process is the same, new advances in technology have led to improvements in the monitoring of the process allowing for reduction of power consumption, tool wear, and total cost of production. Replacing used CNC lathes from the 1980’s in a manufacturing facility may prove costly, thus finding a method to modernize the lathes …

Study Of High Efficiency Micro Thermoelectric Energy Harvesters, Steven Michael Pedrosa

Electronic Theses and Dissertations

Thermal energy sources, including waste heat and thermal radiation from the sun, are important renewable energy resources. Thermal energy can be converted into electricity by thermoelectric phenomena; the thermoelectric phenomena can also be operated in reverse when provided an electric current, producing a temperature gradient across the device. Thermoelectric devices are scalable, renewable, and cost effective products that offer capabilities to harness waste heat or environmental heat sources, and convert the captured heat into usable electricity. The operating principle of a thermoelectric device requires that a temperature gradient be present across the device, which induces the flow of electrons from …

Investigation Into The Potential Use Of Windbreaks To Improve Solar Collector Performance, Michael Watts

All Graduate Theses, Dissertations, and Other Capstone Projects

The global demand for energy is ever increasing; however, the world has a limited number of fossil fuels available. Therefore, alternative renewable energy sources must be utilized. For this reason, solar thermal collectors have become an increasingly popular method for providing hot water or space heating. However, solar thermal collectors are most commonly used in areas that experience warm climates throughout the year. In areas that experience seasonal climates, the cold temperatures and harsh climate conditions significantly reduce the performance of solar thermal collectors during the winter months. This thesis examined the potential that the implementation of a windbreak could …

Autonomous Mobility And Manipulation Of A 9-Dof Wmra, William Garrett Pence

USF Tampa Graduate Theses and Dissertations

The wheelchair-mounted robotic arm (WMRA) is a 9-degree of freedom (DoF) assistive system that consists of a 2-DoF modified commercial power wheelchair and a custom 7-DoF robotic arm. Kinematics and control methodology for the 9-DoF system that combine mobility and manipulation have been previously developed and implemented. This combined control allows the wheelchair and robotic arm to follow a single trajectory based on weighted optimizations. However, for the execution of activities of daily living (ADL) in the real-world environment, modified control techniques have been implemented.

In order to execute macro ADL tasks, such as a "go to and pick up" …

Low-Cost Prosthetic Leg For The Vida Nueva Prosthesis Clinic, Sarah M. Baker, Justin G. Lekos, Jen Van Donk, Kevin Yamauchi

Mechanical Engineering

The Piernas de Vida team partnered with the Vida Nueva Clinic of Prostheses and Orthoses in Choluteca, Honduras to design, plan, and implement a prosthetic foot that could be manufactured entirely by the technicians at the clinic in order to reduce their costs and ultimately allow them to serve more patients each year. Currently, the clinic uses a prefabricated prosthetic lower limb provided by the International Committee of the Red Cross (ICRC) which can be adapted to both transDfemoral and transDtibial patients. The team has successfully developed a foot, currently called the Layer Foot, which can be used by the …

Development Of A Simple Vibration Model For Predicting The Structural Dynamics Of An Hcci Engine, Jeffery A. Massey

Doctoral Dissertations

"The hypothesis tested in this work is that the surface vibration and radiated sound of an engine operating under HCCI combustion is dominated by the free vibration response of the engine's structural components to an impulsive loading brought about by the rapid energy release of the HCCI combustion process. Recent work by the author has shown that classical vibration theory describing the dynamic response of a single-degree-of-freedom (SDOF) oscillator may capture the major characteristics of the engine surface vibrations. Through an experimental investigation of HCCI combustion engine dynamics this model has been developed further.

A band level analysis of measured …

On The Advantages Of E100 Over Gasoline In Down-Sized, Turbo-Charged, Direct-Injected, Variable Valve Actuated, And Stoichiometric S.I. Engines, Alberto A. Boretti

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Current flexi fuel gasoline and ethanol engines have efficiencies generally lower than dedicated gasoline engines. Considering ethanol has a few advantages with reference to gasoline, namely the higher-octane number and the larger heat of vaporization, the paper explores the potentials of dedicated pure ethanol engines using the most advanced techniques available for gasoline engines, specifically direct injection, turbo charging and variable valve actuation. Computations are performed with state-of-the-art, well validated, engine and vehicle performance simulations packages, generally accepted to produce accurate results targeting major trends in engine developments. the higher compression ratio and the higher boost permitted by ethanol allows …