Issues On Finite Element Modeling Of Laminated Composite Structures,
2011
University of Texas at Arlington
Issues On Finite Element Modeling Of Laminated Composite Structures, Farhan Alamgir
Mechanical and Aerospace Engineering Theses - Archive
Composite structures have been used widely in aviation industries and civil construction field because of their high specific stiffness, high specific strength and directional dependent properties. When using finite element method to analyze these structures, special attention of modeling is required. This thesis addresses the effect of layer stresses and displacements of a laminate under loading due to element meshing, boundary constraints and material properties used in modeling of composite structures. This study also includes the investigation of the magnitude and location of the layer peak stresses on modeling the laminate with a hole. It is concluded that special characteristics …
Development Of Ultra-High Temperature Material Characterization Capabilities Using Digital Image Correlation Analysis,
2011
University of Texas at Arlington
Development Of Ultra-High Temperature Material Characterization Capabilities Using Digital Image Correlation Analysis, Julia Elaine Cline
Mechanical and Aerospace Engineering Theses - Archive
Ultra-high temperature deformation measurements are required to characterize the thermo-mechanical response of material systems for thermal protection systems for aerospace applications. The use of conventional surface-contacting strain measurement techniques is not practical in elevated temperature conditions. Technological advancements in digital imaging provide impetus to measure full-field displacement and determine strain fields with sub-pixel accuracy by image processing. In this work, an Instron electromechanical axial testing machine with a custom-designed high temperature gripping mechanism is used to apply quasi-static tensile loads to graphite specimens heated to 2000°F (1093?C). Specimen heating via Joule effect is achieved and maintained with a custom-designed temperature …
Plate Analysis With Different Geometries And Arbitrary Boundary Conditions,
2011
University of Texas at Arlington
Plate Analysis With Different Geometries And Arbitrary Boundary Conditions, Ashwin Balasubramanian
Mechanical and Aerospace Engineering Theses - Archive
This thesis work deals with the study of plates with various geometries and different boundary conditions. The method of study is carried out mainly using the Galerkin method combined with the help of the symbolic algebraic software, Mathematica. In this thesis, flat plates with rectangular and triangular geometries are subjected to uniform load acting normal to their surfaces. The lateral deflection of the plates is expressed in a series of polynomials which satisfy the homogenous boundary conditions. Mathematica is used in handling the algebraic operations to solve for the coefficients and generating the trial functions. The maximum deflection of the …
Consideration Of Compressibility Effects For Applied-Back-Pressure Dynamic Well Control Response To A Gas Kick In Managed Pressure Drilling Operations,
2011
University of Texas at Arlington
Consideration Of Compressibility Effects For Applied-Back-Pressure Dynamic Well Control Response To A Gas Kick In Managed Pressure Drilling Operations, William Alexander Bacon
Mechanical and Aerospace Engineering Theses - Archive
Managed Pressure Drilling (MPD) operations offer the ability to control a relatively small gas kick dynamically, without shutting in the well using blowout preventers. One currently employed method of dynamic well control uses applied-back-pressure to force flow exiting the wellbore to equal flow entering the drill-pipe, which is taken as an indication that the influx has stopped. However, for flow out equals flow in to imply influx cessation, the assumption of incompressibility of fluid in the wellbore is necessary. When fluid compressibility is appreciable, solely ensuring flow rate continuity does not necessarily imply influx cessation. The period of "dynamic well …
Numerical Analysis Of The Interaction Between A Detonation Wave And Compressible Homogeneous Isotropic Turbulence,
2011
University of Texas at Arlington
Numerical Analysis Of The Interaction Between A Detonation Wave And Compressible Homogeneous Isotropic Turbulence, Monika Chauhan
Mechanical and Aerospace Engineering Theses - Archive
A numerical study was performed to investigate the effect of preshock turbulence on the detonation wave properties. A direct numerical simulation was performed on the chemically reactive Navier-Stokes equations using a Runge-Kutta scheme and a fifth-order WENO spatial discretization. We performed a direct numerical simulation (DNS) which belongs to the domain of Computational Fluid Dynamics (CFD), of the fluid mechanics equations in three dimensions to determine the fine scale evolution. A simple one-step chemical kinetics model was used in the study.The main objective of the research is to examine the behavior of the turbulence when subjected to a strong shock …
Airfoil-Shaped Extension-Twist-Coupled Composite Star-Beams For Rotor Blade Tip Applications,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
University of Texas at Arlington
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,
2011
The University of Akron, Main Campus
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.
