Engineering Commons^™

Numerical Investigation On Charring Ablator Geometric Effects: Study Of Stardust Sample Return Capsule Heat Shield, Haoyue Weng, Alexandre Martin

Mechanical Engineering Faculty Publications

Sample geometry is very influential in small charring ablative articles where 1D assumption might not be accurate. In heat shield design, 1D is often assumed since the nose radius is much larger than the thickness of charring. Whether the 1D assumption is valid for the heat shield is unknown. Therefore, the geometric effects of Stardust sample return capsule heat shield are numerically studied using a material response program. The developed computer program models material charring, conductive heat transfer, surface energy balance, pyrolysis gas transport and orthotropic material properties in 3D Cartesian coordinates. Simulation results show that the centerline temperatures predicted …

A Multi-Scale Based Model For Composite Materials With Embedded Pzt Filaments For Energy Harvesting, A.E. El-Etriby, M.E. Abdel-Meguid, K.M. Shalan, Tarek Hatem, Yehia Bahei-El-Din

Centre for Advanced Materials

Ambient vibrations are major source of wasted energy, exploiting properly such vibration can be converted to valuable energy and harvested to power up devices, i.e. electronic devices. Accordingly, energy harvesting using smart structures with active piezoelectric ceramics has gained wide interest over the past few years as a method for converting such wasted energy. This paper provides numerical and experimental analysis of piezoelectric fiber based composites for energy harvesting applications proposing a multi-scale modeling approach coupled with experimental verification. The multi-scale approach suggested predicting the behavior of piezoelectric fiber-based composites use micromechanical model based on Transformation Field Analysis (TFA) to …

Intelligent Control Of Miniature Holonomic Vertical Take-Off And Landing Robot, Mohammad A. Jaradata, Mohamed Al-Fandia, Omar Alkhatiba, Yousef Sardahi

All Engineering Faculty Research

This paper discusses the development of a fuzzy based controller for miniaturized unmanned aerial vehicle (UAV).This controller is designed to control the center-of-gravity (CoG) in a new configuration of coaxial miniaturized flying robot (MFR). The idea is to shift the CoG by controlling two pendulums located in perpendicular directions; each pendulum ends with a small mass. A key feature of this work is that the control algorithm represents the original nonlinear function that describes the dynamics of the proposed system. The controller model incorporates two cascaded subsystems: PD and PI fuzzy logic controllers. These two controllers regulate the attitude and …

Identification Of Geostationary Satellites Using Polarization Data From Unresolved Images, Andy Speicher

Electronic Theses and Dissertations

In order to protect critical military and commercial space assets, the United States Space Surveillance Network must have the ability to positively identify and characterize all space objects. Unfortunately, positive identification and characterization of space objects is a manual and labor intensive process today since even large telescopes cannot provide resolved images of most space objects. Since resolved images of geosynchronous satellites are not technically feasible with current technology, another method of distinguishing space objects was explored that exploits the polarization signature from unresolved images.

The objective of this study was to collect and analyze visible-spectrum polarization data from unresolved …

The Milton Lehman Papers, Milton Lehman

Finding Aids

Milton Lehman (1917-1966) was a free-lance writer, contributing about 250 articles to national magazines such as Saturday Evening Post, Life, Reader’s Digest, McCall’s, Look, The York Times, and other periodicals, books and newspapers. He wrote a biography of Robert H. Goddard that was published in 1963. He was helped throughout the seven year writing process by Esther C. Goddard, Goddard’s wife, who supplied him with transcripts of Goddard’s notes, notebooks, diaries, reports and correspondence and with photographs of his work as well as her own recollections. Lehman interviewed people from all parts of Goddard’s life; his childhood, schooling, early Clark …

Cavity Ignition In Supersonic Flow By Spark Discharge And Pulse Detonation, Timothy M. Ombrello, Campbell D. Carter, Chung-Jen Tam, Kuang-Yu Hsu

United States Air Force: Publications

Ignition of an ethylene fueled cavity in a supersonic flow was achieved through the application of two energy deposition techniques: a spark discharge and pulse detonator (PD). High-frequency shadowgraph and chemiluminescence imaging showed that the spark discharge ignition was passive with the ignition kernel and ensuing flame propagation following the cavity flowfield. The PD produced a high-pressure and temperature exhaust that allowed for ignition at lower tunnel temperatures and pressures than the spark discharge, but also caused significant disruption to the cavity flowfield dynamics. Under certain cavity fueling conditions a multiple regime ignition process occurred with the PD that led …

Absorption Properties Of Type-Ii Inas/Inassb Superlattices Measured By Spectroscopic Ellipsometry, P T. Webster, N A. Riordan, S Liu, E H. Steenbergen, R A. Synowicki, Y H. Zhang, S R. Johnson

United States Air Force: Publications

Strain-balanced InAs/InAsSb superlattices offer access to the mid- to long-wavelength infrared region with what is essentially a ternary material system at the GaSb lattice constant. The absorption coefficients of InAs/InAsSb superlattices grown by molecular beam epitaxy on (100)-oriented GaSb substrates are measured at room temperature over the 30 to 800 meV photon energy range using spectroscopic ellipsometry, and the miniband structure of each superlattice is calculated using a Kronig-Penney model. The InAs/InAsSb conduction band offset is used as a fitting parameter to align the calculated superlattice ground state transition energy to the measured absorption onset at room temperature and to …

Three-Dimensional Indeterminate Impacts In Legged Robotic Locomotion, Abhishek Chatterjee

Mechanical and Aerospace Engineering Theses - Archive

Legged robotic systems undergo a large number of impacts during walking or running tasks. These impacts occur over the surface of contact between the feet and the ground. If a rigid body assumption is held, these impacts can be analyzed by selecting a certain number of points on the impacting bodies. A minimum of three points are required for analyzing a surface contact on a plane. However, using a minimum number of points for analyzing surface impact would require an additional analysis for appropriately selecting these points. On the other hand, if a large number of evenly distributed impact points …

Biomechanical Analysis Of The Cornea To Improve Post Surgical Outcomes Through Finite Element Analysis, Salman Nasir Khan

Mechanical and Aerospace Engineering Dissertations - Archive

Vision deterioration is a major healthcare concern. It is estimated that one in three persons develops some form of vision reducing eye disease by the age of 65 and these numbers are expected to increase. Deterioration in visual acuity is due to ocular diseases that change the shape or clarity of the cornea. Health/shape of the cornea is extremely important as it determines the refractive power of the eye.This work studies ocular surgeries from a mechanical/structural engineering perspective. It begins by discussing laser in-situ keratomileusis (LASIK) surgery and explains the role of lasers in modifying the corneal shape to improve …

Design Of Cooling And Ventilation Of Telecommunication Shelter At High Altitude, Palak Patel

Mechanical and Aerospace Engineering Theses - Archive

Telecommunication shelters house information technology (IT), networking, power, and cooling equipment such as racks, power cabinets, batteries, fans, etc. For reliable operation of the IT and networking equipment, shelters need to satisfy or exceed minimum environmental guidelines for all equipment they contain. These guidelines typically contain specified operational temperature, maximum gaseous and particular contaminant levels. In this work, cooling and ventilation needs of a telecommunication shelter at an altitude of 9,678 feet are studied by modeling the system and simulating various operational and weather scenarios using FloVENT 10.1, a computational fluid dynamics (CFD) tool. The shelter contains two compartments: the …

Experimental And Computatonal Analysis Of The Effect Of Pcb Layer Copper Thickness And Prepreg Layer Stiffness On Solder Joint Reliability, Sanjay Mahesan Revathi

Mechanical and Aerospace Engineering Theses - Archive

The emphasis of this study is to find out how the solder joints of the BGA package are affected with change in the stack up PCB layer copper thickness and the prepeg layer stiffness. In general the effect of the PCB layer thickness is to increase the stress and strain range and to decrease the thermal fatigue life. Basically a PCB consists of different layers with different material properties (Eg: Cu, FR4 etc.).In this paper we deal with the PCB with 1-6-1 configuration (6 core layers and 1 prepeg layer on the top and bottom). A Prepeg is a fiber …

Study Of Hotspot Cooling For Integrated Circuits Using Electrowetting On Dielectric Digital Microfluidic System, Govindraj Shreyas Bindiganavale

Mechanical and Aerospace Engineering Dissertations - Archive

Thermal management in electronics is an ever-growing challenge which needs constant innovations to regulate hotspots in integrated circuits for safe operation within its Thermal Design Power (TDP) envelope. As the number of transistors increase due to advancements in photolithography to enable die shrink, portable electronics are on the rise and so is the demand for microscale cooling systems because conventional cooling components like heat sinks, heat pipes and fans are not capable of meeting design requirements for cooling solutions. In addition to the benefits enjoyed by microscale cooling systems like compact and lightweight design along with simple operation, electrowetting on …

Accurate Three-Dimensional Characterization Of The Nonlinear Material Constitutive Properties For Laminated Composite Materials, Julia Elaine Cline

Mechanical and Aerospace Engineering Dissertations - Archive

Accurate and efficient full three-dimensional characterization of mechanical properties of composite materials, including stress-strain curves and strength characteristics, is essential for understanding complex deformation and failure mechanisms of composites and optimizing material qualification efforts. Non-contact full-field deformation measurement techniques such as digital image correlation (DIC) allowing for assessment of all surface strain components on the entire specimen surface, enable simpler experimental setups and material specimen designs for more efficient and accurate material characterization. This work presents a new method enabling simultaneous assessment of the shear stress-strain curves in all three principal material planes. The method uses a small rectangular plate …

Structural Integrity Of Tsvs In 3d Package Under Thermal Loading, Parinda Patel

Mechanical and Aerospace Engineering Theses - Archive

In this advanced technological era, all electronic equipments tend to be light in weight, and have high performance with low power consumption and low prices. Gain in both performance and cost via Moore's law is starting becoming difficult post 28nm technology node. Three dimensional chips staking with TSV technology has gained momentum to meet such requirements of significant miniaturization and power reduction which result in increased performance. Vertically interconnected TSVs provide the shorter effective electrical interconnect path, resulting in reduced signal latency between strata and greater signal bandwidth. Moreover, TSVs offer high density integration, increased number of input/output terminals and …

Considerations For Generating Accurate Linear Transfer Functions For Laminar Flow Transmission Line Dynamics, Sina Jasteh

Mechanical and Aerospace Engineering Theses - Archive

Modeling fluid lines for applications such as hydraulic fracturing has been studied for many years, and we know that the inverse frequency method presents very accurate solutions for systems with lines in almost all laminar flow cases. However, utilizing this method is not easy for all users, and requires experience and understanding of the method. In this study a simplified method is introduced for accurately modeling the transients in lines which requires minimum experience in utilizing inverse frequency methods; the accuracy and limits of this simplified method are studied. Also, alternative approaches are presented which improved the accuracy of the …

Optimal Design Of A Parallel Beam System With Elastic Supports To Minimize Flexural Response To Harmonic Loading, Bret R. Hauser

Mechanical and Aerospace Engineering Theses - Archive

Mechanical systems subject to vibration are prevalent across many industries. Harmonic problems can be especially challenging to optimize due to the likelihood that the response will be multi-modal; influenced by system natural frequencies throughout the design space. Further, analysis of these systems often involves large and complex computer models which require significant resources to execute. A parallel beam system, as evaluated with Finite Element Modeling (FEM), is used as an example in this work to demonstrate a proposed method of identifying an optimum in a constrained, multi-modal response environment with consideration for Expensive Black Box Functions. The presented method leverages …

Effects Of Transverse Shear Deformation On Composite Beams With Various Laminate Configurations And Boundary Conditions, Wei-Tsen Lu

Mechanical and Aerospace Engineering Theses - Archive

Analytical methods are developed for determining deflection of composite beams under transverse load with various boundary conditions and laminate configurations. The present methods include development of expression for 1-D equivalent bending stiffness with and without presence of twisting curvature and prediction of the beam deflection accounting for transverse shear effect. Finite element analysis of 3-D ANSYS models is conducted by using Solid186 elements. The present analytical model is executed by using MATLAB program. Both analytical and FEM models were first validated by using isotropic material in the model and comparing the existing solutions. The composite beams with rectangular cross-section and …

Novel Neuro-Dynamic Methods For Solving Robotic Planning And Control Problems, Ghassan M. Atmeh

Mechanical and Aerospace Engineering Dissertations - Archive

Robotic systems are growing more complex to cater to the tasks they are required to solve. Irrespective of these tasks the problem of planning and control must be solved for all robotic systems. In this dissertation a general description of that problem is given along with the issues that it faces. This problem concerns planning a trajectory in the operational space of the robot, i.e. the space in which a task is to be executed. Then solving the inverse kinematics problem to compute the joint positions that correspond to that trajectory. And lastly, controlling the robot to track those joint …

Reduced-Order Analysis Of Dual Mode Supersonic Combustion Ramjet Propulsion System, Vijay Gopal

Mechanical and Aerospace Engineering Theses - Archive

High speed propulsion systems typically possess relatively simple geometry but the complexity involved in the flow characteristics makes their analysis a challenging task. The current research work introduces a reduced order analytical model for a steady operation of dual mode SCRamjet (Supersonic Combustion Ramjet) propulsion system at design and off-design conditions. The model hopes to reduce analysis time and complexity to carry out parametric sweep studies for preliminary design of SCRamjet engines. The analytical model splits the analysis of SCRamjet engine into five interactive components namely: inlet, isolator, injector, burner and nozzle. Each component is modelled using physics of gas-dynamics …

Viscoelastic Effects On A Polyetherimide Cylinder With Constant Radial Deformation, Louis Edward Parkman

Mechanical and Aerospace Engineering Theses - Archive

The relaxation of an axisymmetric radially crimped joint is analyzed with the inner component being formed from the engineering grade polymer ULTEM^TM 1000 polyetherimide. Creep and Relaxation tests were performed at several temperatures in order to use Time Temperature Superposition theory to assemble a master curve for predictions at long times based on short time testing. The master curves for each test were fit to the appropriate Prony Series and all coefficients are tabulated for re-use. The elastic theory for the classic thick walled cylinder was reviewed and the conversion from elasticity to viscoelasticity was demonstrated. Strength predictions are …

Development Of A Numerical Tool To Study The Mixing Phenomenon Occurring During Mode One Operation Of A Multi-Mode Ejector-Augmented Pulsed Detonation Rocket Engine, Joshua Dawson

Mechanical and Aerospace Engineering Theses - Archive

A novel multi-mode implementation of a pulsed detonation engine, put forth by Wilson et al. [2], consists of four modes; each specifically designed to capitalize on flow features unique to the various flow regimes. This design enables the propulsion system to generate thrust through the entire flow regime. The multi-mode ejectoraugmented pulsed detonation rocket engine operates in mode one during take-o_ conditions through the acceleration to supersonic speeds. Once the mixing chamber internal flow exceeds supersonic speed, the propulsion system transitions to mode two. While operating in mode two, supersonic air is compressed in the mixing chamber by an upstream …

Use Of A Windbreaker To Mitigate High Speed Wind Loading On A Modular Data Center, Prasad Pramod Revankar

Mechanical and Aerospace Engineering Theses - Archive

The data centers that are located in open regions are subjected to various environmental risks. Earthquakes and very strong winds have the greatest effect on the structural integrity of the data centers. As the wind blows against the external structure, there is a buildup of pressure against the external structure which is translated to the supporting structure. Certain components of the data center like the inlet and exhaust dampers cannot withstand high wind speeds. Various kinds of fences have been used as windbreakers to prevent wind induced damage to objects. A windbreaker basically acts as a barrier to the upstream …

The Configurator: A Novel Approach To Enterprise Configuration Of Complex Software Systems, Thomas K. Wang

Mechanical and Aerospace Engineering Theses - Archive

Software systems are ubiquitous within aerospace technology. They are essentially the guidance, navigation, and control (GNC) of aircraft and satellites. Software systems are a primary component of satellite ground control systems, as well. Similarly, radar systems heavily utilize software systems. The design of aerospace software systems presents challenges outside of traditional aerospace or computer science domains. Mission operability and design constraints are balancing factors critical to the implementation phase of ground control software systems. Therefore, design decisions can often complicate the system architecture. Complexities within the architecture inevitably lead to challenges in the system integration phase. Numerous software source code …

Performance Evaluation Of Compliant Foil Seal, Sashidhar Raghuraman

Mechanical and Aerospace Engineering Theses - Archive

The concept of foil bearings has gained large acceptance in the industry and is been applied for various rotating equipment including air cycle machines, cryogenic turbo-expanders, centrifugal compressors and gas turbine engines. The ever-increasing demand for maintenance free and durable components has led to the development of compliant foil seals (CFS). Labyrinth and Brush seals have been widely employed for reducing the leakage flow at high pressure and temperature conditions, to enhance the overall performance of the system. Increase in the radial clearance to compensate the lack of their capability to accommodate the higher rotor orbits results in more leakage. …

Design And Structural Of A Fence Used For Protecting Modular Data Center From High Speed Wind, Nikhil Baviskar

Mechanical and Aerospace Engineering Theses - Archive

Various data centers built in an open area are occasionally susceptible to different kinds of natural calamities. Wind, either from any of the sources like hurricane, tornado or storm is one of those ecological dangers with high speed flow. These high speed winds can be responsible for downed power lines, trees and collapsing of buildings as well, the wind may adversely impact a data center’s structure. Windbreaker or wind fence is basically used to reduce the high speed of the wind resulting in the protection of structures or objects behind it. Some modular data centers which encounter problems of high …

Sustainable Methodology For The Use Of Fuel Cells In Data Centers, Vignesh Balasubramanian

Mechanical and Aerospace Engineering Theses - Archive

Data centers have become the lynchpin of the modern economy - from the small to medium-sized organizations, to the enterprise data centers that operates American corporations and the server farms that operate cloud-computing services accommodated by Facebook, Amazon, Google, and others. The booming of cloud storage, extensive data analysis, e-commerce, and internet traffic is also making data centers one of the rapidly growing clients of electricity in developing countries, and one of the key drivers in the construction of new power plants. Key researches are carried out for sustainable development of power usage in data centers. Fuel cells have gone …

Semi-Active Suspension System Using A Magnetorheological Damper, Abinav Suresh

Mechanical and Aerospace Engineering Theses - Archive

Magnetorheological (MR) Fluid changes its yield strength when it is subjected to a magnetic field. When this fluid is used inside a damper, it has the ability to change the damping coefficients when it is acted upon by magnetic fields. In this experiment, a MR damper was tested on a shock dyno, where characteristics of the damper was found. Three parameters were changed during the course of the experiment, namely: electric current supplied through the solenoid of the damper, displacement amplitude of the piston and driving frequency of the motor. The results show that there was an increase in damping …

Development Of Alkali Chlorides As Heat Transfer Fluids With Addition Of Nanoparticles, Sriram Sambasivam

Mechanical and Aerospace Engineering Theses - Archive

Recent studies have shown that using a single fluid for Heat Transfer and Thermal Energy Storage, improves the working and efficiency of a CSP. It improves the conversion efficiency (thermal energy to electrical) and also reduce the thermal losses due to heat exchangers by eliminating them. Other methods of storage are thermo chemical TES or phase change TES, but they require heat exchanger between HTF and TES medium, due to which the thermal losses between them are significant. CSP works on a conventional thermodynamic cycle (Rankine Cycle, Brayton Cycle) indicating that higher operating temperature are required to achieve higher efficiency. …

Dynamics And Control Of The Smart Maintenance And Inspection Robotic Free-Flyer (Smirff), Ameya Rajendra Godbole

Mechanical and Aerospace Engineering Theses - Archive

The aim of the future space missions would be exploring near earth planets and asteroids. This would mean longer flight durations requiring a space habitat. Longer flight durations would require frequent maintenance and repairs of the space habitat. This would involve the risk of exposing astronauts to the harsh environments while conducting extra-vehicular activities. This risk can be minimised by using a tele-operated free- flying robot. Free- flying robots are a unique class of robots which do not have rigid fixed base and oat in space. A concept of Smart Maintenance Inspection and Robotic Free- flyer (SMIRFF) is presented in …

Analysis Of A Composite Beam With Unsymmetrical C Crossection, Martin M. Kora

Mechanical and Aerospace Engineering Theses - Archive

The research work focuses on analysis of composite beam, where a closed form analytical solution was developed to determine the sectional properties of composite beam with unsymmetrical C cross section. The sectional properties such as centroid, equivalent axial stiffness and equivalent bending stiffness are computed. A parametric study of shear center and centroid with different layup sequences was conducted using the developed solution. The ply stresses developed in the C beam is also calculated analytically and is verified by finite element analysis. The result from the proposed theory gives excellent agreement with the ANSYS™