Aerospace Engineering Commons^™

Mechanics Of Pure Bending And Eccentric Buckling In High-Strain Composite Structures, Jimesh D. Bhagatji, Oleksandr G. Kravchenko, Sharanabasaweshwara Asundi

Mechanical & Aerospace Engineering Faculty Publications

To maximize the capabilities of nano- and micro-class satellites, which are limited by their size, weight, and power, advancements in deployable mechanisms with a high deployable surface area to packaging volume ratio are necessary. Without progress in understanding the mechanics of high-strain materials and structures, the development of compact deployable mechanisms for this class of satellites would be difficult. This paper presents fabrication, experimental testing, and progressive failure modeling to study the deformation of an ultra-thin composite beam. The research study examines the deformation modes of a post-deployed boom under repetitive pure bending loads using a four-point bending setup and …

Damage Initiation Of 15v38 Steel Bar During Square-To-Round Hot Rolling Process, Siva Sai Krishna Dasari, Henry Adekola Haffner, K. Chandrashekhara, Mario F. Buchley, Simon N. Lekakh, Ronald J. O'Malley

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Hot rolling processes have been extensively used to produce round bars by reducing the cross-sectional area of continuously cast steel. The current trend toward increasing productivity often requires a more aggressive reduction per pass. Establishing safe and optimized hot rolling parameters must be determined to avoid damage while deforming the specific steel composition. Understanding the damage mechanism during the metal forming process is vital for product quality. Herein, a combined experimental and simulation approach is developed to track the evolution potential damage during hot bar rolling. Hot tension tests are conducted on as-cast vanadium micro alloyed 15V38 steel at different …

Effect Of Post-Cured Through Thickness Reinforcement On Disbonding Behavior In Skin-Stringer Configuration, Jimesh D. Bhagatji, Christopher Morris, Yogaraja Sridhar, Bodhisatwa Bhattacharjee, Krishnanand N. Kaipa, Oleksandr G. Kravchenko

Mechanical & Aerospace Engineering Faculty Publications

An experimental investigation of interlaminar toughness for post-cured through-thickness reinforcement (PTTR) skin-stringer sub-element is presented. The improvement in the crack resistance capability of skin-stringer samples was shown through experimental testing and finite element analysis (FEA) modeling. The performance of PTTR was evaluated on a pristine and initial-disbond of the skin-stringer specimen. A macro-scale pin-spring modeling approach was employed in FEA using a non-linear spring to capture the pin failure under the mixed-mode load. The experimental results showed a 15.5% and 20.9% increase in strength for the pristine-PTTR and initial-disbond PTTR specimens, respectively. The modeling approach accurately represents the overall structural …

Aeroelastic Phenomena Of Fixed-Wing Aircraft In Transonic And Supersonic Flows Using A Tightly-Coupled Computational Approach, John C. Havenar

College of Graduate Studies: Theses & Dissertations

Aeroelastic phenomena encountered during flight have considerable effects on the aerodynamic characteristics of fixed-wing aircraft. Transonic aeroelastic phenomena are often characterized by unique flow features which have complex ramifications for aircraft in transonic flight. Computational study of high-speed aeroelastic phenomena requires a fully-coupled aeroelastic algorithm. A series of wing designs are studied with a computational finite volume method solver accompanied by a finite element method solver for the calculation of structural deformation. The computational model for the flow field is validated with experimental data. Modeled flight conditions include transonic flows with bordering subsonic and supersonic cases included for completeness. The …

Mathematical Modeling: Finite Element Analysis And Computations Arising In Fluid Dynamics And Biological Applications, Jorge Reyes

UNLV Theses, Dissertations, Professional Papers, and Capstones

It is often the case when attempting to capture real word phenomena that the resulting mathematical model is too difficult and even not feasible to be solved analytically. As a result, a computational approach is required and there exists many different methods to numerically solve models described by systems of partial differential equations. The Finite Element Method is one of them and it was pursued herein.This dissertation focuses on the finite element analysis and corresponding numerical computations of several different models. The first part consists of a study on two different fluid flow models: the main governing model of fluid …

Nonlinear Dynamics Analysis And Control Of Space Vehicles With Flexible Structures, Marco Fagetti

Doctoral Dissertations and Master's Theses

Space vehicles that implement hardware such as antennas, solar panels, and other extended appendages necessary for their respective missions must consider the nonlinear rotational and vibrational dynamics of these flexible structures. Formulation and analysis of these flexible structures must account for the rigid-flexible coupling present in the system dynamics for stability analysis and control design. The system model is represented by a flexible appendage attached to a central rigid body, where the flexible appendage is modeled as a cantilevered Euler-Bernoulli beam. Discretization techniques, such as the assumed modes method and the finite element method, are used to model the coupled …

Parallel Anisotropic Unstructured Grid Adaptation, Christos Tsolakis, Nikos Chrisochoides, Michael A. Park, Adrien Loseille, Todd Michal

Computer Science Faculty Publications

Computational fluid dynamics (CFD) has become critical to the design and analysis of aerospace vehicles. Parallel grid adaptation that resolves multiple scales with anisotropy is identified as one of the challenges in the CFD Vision 2030 Study to increase the capacity and capability of CFD simulation. The study also cautions that computer architectures are undergoing a radical change, and dramatic increases in algorithm concurrency will be required to exploit full performance. This paper reviews four different methods to parallel anisotropic grid adaptation. They cover both ends of the spectrum: 1) using existing state-of-the-art software optimized for a single core and …

Development Of Triangular And Tetrahedral Finite Elements For Solutions To Thermoelastic Instabilities Using Hotspotter, Cortney Samuel Leneave

Electronic Theses and Dissertations

The objective of the work presented in this thesis is to develop first-order triangular and tetrahedral elements for solutions to Thermoelastic Instabilities (TEI) regarding sliding friction systems in Hotspotter.

Hotspotter software uses a finite element method and an eigenvalue method and is an important tool because currently no other commercial software exists which solves the TEI problem for critical velocities and wave numbers of a system. Hotspotter currently uses quadrilateral and hexahedral elements for two and three dimensional analysis, respectively. Typically, tri and tet elements are used in industry when doing static and dynamic stress analysis. Therefore, the Hotspotter user …

Numerical Analysis And Fluid Flow Modeling Of Incompressible Navier-Stokes Equations, Tahj Hill

UNLV Theses, Dissertations, Professional Papers, and Capstones

The Navier-Stokes equations (NSE) are an essential set of partial differential equations for governing the motion of fluids. In this paper, we will study the NSE for an incompressible flow, one which density ρ = ρ0 is constant.

First, we will present the derivation of the NSE and discuss solutions and boundary conditions for the equations. We will then discuss the Reynolds number, a dimensionless number that is important in the observations of fluid flow patterns. We will study the NSE at various Reynolds numbers, and use the Reynolds number to write the NSE in a nondimensional form.

We will …

Surface Roughness Formation During Tensile Plastic Deformation Of Nickel Polycrystals, Kranthi Balusu

Mechanical and Aerospace Engineering Dissertations - Archive

Understanding the formation of surface roughness could help better diagnose a metal component’s health and could potentially help in making better microstructure design decisions. Both of these, in turn, contribute to the design of efficient structural components. In this work, the research objective is to understand the relationship between the surface microstructure (i.e., grain orientations) and the surface-height changes in nickel polycrystals undergoing small amounts of tensile plastic deformation. The secondary objective is to determine the relationship between surface height and strain localization. Primarily simulations were used, along with experimental surface roughness observations, to validate the simulation results. Discrete dislocation …

A Study Of Effect Of Bond Length On Bond Strength Using Transient Heat Transfer Analysis, Junaid Mohamed Baig

Mechanical and Aerospace Engineering Theses - Archive

It is important to understand the mechanical properties of the bonding between the adjacent layers of 3D printed parts build by fused deposition modeling. The bonding process is highly nonlinear and depends on various geometrical and thermal process parameters. This work aims to quantify the degree of bonding by calculating bond potential between the extruded layers using finite element heat transfer analysis. Successive transient analysis were carried out using this model by constantly updating the boundary conditions and geometric model during the deposition of the extruded bead. Temperatures at critical points were calculated over a period to calculate the bond …

Multi-Mesh Reduced-Order Basis Method For Finite Element Analysis, Ashkan Akbariyeh

Mechanical and Aerospace Engineering Dissertations - Archive

Reduced order modeling of differential equations parametrized over a parameter space can be used to accelerate optimization and parameter estimation problems. The method of snapshots or reduced order basis is well established among researchers as a tool to build reduced order models of ordinary differential equations. The reduced order basis method has been utilized for numerical solution of parametric PDE problems by researchers in recent years and has many advantages over response surface methods. The application of ROB to finite element analysis has been restricted to using a fixed mesh for snapshots. In this work, a new method is developed …

Influence Of Relative Density And Microstructural Anisotropy On The Global Elastic Properties Of Cellular Structures, Justin Compton

Mechanical and Aerospace Engineering Theses - Archive

The favorable strength-to-weight ratio of cellular solids makes them ideal for structural applications. With the advent of additive manufacturing, the fabrication of complex cellular structures is becoming a reality. It is therefore necessary to understand the mechanical properties of cellular structures. The global mechanical properties of cellular structures are governed by geometry and therefore, differ from the mechanical properties of the base material from which they are constructed. In this study, finite element models are developed to explore the effective elastic properties of honeycomb structures for isotropic and anisotropic microstructural material properties. Finite element models are generated for regular, hexagonal …

Analysis Of Additively Manufactured Lattice Structures Using Finite Element Methods, Christopher A. Box

Theses and Dissertations

Additive Manufacturing (AM) processes are well known for their ability to fabricate parts with complex geometries. Lattice structures leverage this ability to create parts with high strength-to-weight ratio and other desirable structural qualities. This research presents a parameterized modeling tool using common Finite Element Analysis (FEA) and scripting software with which aggregated lattice structures can be analyzed, given different geometric properties and loading conditions. A full factorial Design of Experiments is run to explore the effects of various parameters on the strength of lattice structures. Experimental compressive strength results from three FDM-produced PLA lattices are discussed and compared to predictions …

Finite Element Simulation Of Pzt-Aided Interrogation Of Composite Laminates Exhibiting Damage, Amany Micheal, Yehia Bahei-El-Din

Centre for Advanced Materials

Piezoelectricity has proved effective in capturing changes in structures caused by various damage mechanisms. In one approach, piezoelectric wafer active sensors (PWAS) are mounted on the surface of the host structure and utilized as both actuators and sensors to interrogate the structure and monitor its health. This is achieved by subjecting the PWAS to a transient electric pulse and reading the resulting voltage. Changes in the stiffness of the substrate due to structural damage affect the response of the PWAS, which could be correlated to integrity of the structure. Applying this technique to fibrous composite laminates encounters particular challenges due …

3d Fe Modelling Of Die Stress And Wear In Non-Isothermal Forging Of Ti–6al–4v Turbine Blade, Shiyuan Luo, Dahu Zhu, Lin Hua, Dongsheng Qian, Sijie Yan

The 8th International Conference on Physical and Numerical Simulation of Materials Processing

No abstract provided.

Finite Element Based Cross-Sectional Buckling Optimization For A Constant Area, Pinned-Pinned Composite Column, Anirudh Srinivas

Mechanical and Aerospace Engineering Theses - Archive

In archery, dynamic buckling compromises the target accuracy of arrows. For both dynamic and quasi-static buckling, the buckling load depends on the cross-sectional area moment of inertia, which can be increased by modifying the cross-sectional shape of the arrow shaft. Arrows commercially available today are made up of composite materials and have a tubular circular cross-section. In this study an effort has been made to optimize the cross-sectional shape of the composite arrow shaft, using finite element based, quasi-static buckling analysis keeping the length and area of the cross-section constant. The composite column is pinned at both ends and is …

Finite Element Based Weight Reduction Subject To Stability Constraints For An Airship Composite Duct, Soham M. Umbrajkar

Mechanical and Aerospace Engineering Theses - Archive

The primary functions of High Altitude Long Endurance (HALE) airships are persistent observation and wide area direct line of sight communication. Traditional airships have an ellipsoidal type hull, which is characterized by a large aspect ratio but results in an increase in the weight of the envelope. In order to reduce the weight of an airship, a hull having lower aspect ratio would be preferred. A novel unconventional airship design having a toroidal geometry with a propulsive duct running from the front end to back end was developed by Dancila in an attempt to achieve this objective. The propulsive duct …

Conceptual Design, Structural Analysis, And Design Space Exploration Of A Vacuum Lighter Than Air Vehicle, Brian C. Cranston

Theses and Dissertations

The research detailed in this study investigates an internal vacuum as well as its optimal structural design, utilizing currently available materials, as an alternative to traditional gases to create and sustain buoyancy in lighter than air vehicles. To date, the consideration of a vacuum lighter than air vehicle has been limited to three sources of literature, the earliest of which dates back to 1663. This study will initially summarize and review this literature. We will then combine finite element analysis, dimensional analysis, design of experiments, and response surface methodology studies to explore the feasibility, and the functional design of a …

Finite Element Analysis And Experimentation Of An Icosahedron Frame Under Compression, Mohammed Alghofaily

Theses and Dissertations

A nonlinear analysis of a 3D icosahedron frame was conducted using ABAQUS, under a compressive load in which collapse occurs. The frame was created in SolidWorks using the material properties of the 3D plastic building material VeroBlue. Two considerations were made: the computational features of the frame, and the comparison between the experimental solution to the numerical solution. Two studies were also considered in this research: The first study was a comparison between the seven-inch and the four-inch icosahedron model with identical weight to buoyancy ratios; and the second study was a comparison between the seven-inch icosahedrons frame, with the …

Dynamic Response Analysis Of An Icosahedron Shaped Lighter Than Air Vehicle, Lucas W. Just

Theses and Dissertations

The creation of a lighter than air vehicle using an inner vacuum instead of a lifting gas is considered. Specifically, the icosahedron shape is investigated as a design that will enable the structure to achieve positive buoyancy while resisting collapse from the atmospheric pressure applied. This research analyzes the dynamic response characteristics of the design, and examines the accuracy of the finite element model used in previous research by conducting experimental testing. The techniques incorporated in the finite element model are confirmed based on the experimental results using a modal analysis. The experimental setup designed will allow future research on …

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 …

Numerical Simulations Of Surface Charging At The Lunar Terminator, Daoru Frank Han, Joseph J. Wang

Mechanical and Aerospace Engineering Faculty Research & Creative Works

A full-particle particle-in-cell (PIC) simulation model is developed to perform fully-kinetic simulations of surface-plasma interactions at the lunar terminator region. This model uses a non-homogeneous immersed-finite-element (IFE) solver to calculate the electric field discontinuity (flux jump) at the plasma-surface interface and surface charging for realistic lunar surface terrain. The simulation includes all plasma species, including the solar wind electrons and ions, as well as photoelectrons with real proton-to-electron mass ratio so the kinetic properties in the mesothermal flow are resolved. We present simulation results of surface charging around a lunar hill at the lunar terminator region.

A Continuous/Discontinuous Fe Method For The 3d Incompressible Flow Equations, Nikolaos Kyriazis

Doctoral Dissertations and Master's Theses

A projection scheme for the numerical solution of the incompressible Navier-Strokes equation is presented. Finite element discontinuous Galerkin (dG) discretization for the velocity in the momentum equations is employed. The incompressibility constraint is enforced by numerically solving the Poisson equation for pressure using a continuous Galerkin (cG) discretization. The main advantage of the method is that is does not require the velocity and pressure approximation spaces to satisfy the usual inf-sup condition, thus equal order finite element approximations for both velocity and pressure can be used. Furthermore, by using cG discretization for the Poisson equation, no auxiliary equations are needed …

A Finite Element Analysis Of A Carbon Fiber Composite Micro Air Vehicle Wing, Theodore A. Szelag

Theses and Dissertations

Micro-air vehicles (MAV)s provide a valuable and low observable way to do the jobs that the Air Force deems to be dull, dirty and dangerous. Basing the design of an MAV wing on that of a biological counterpart will provide a proven design that is capable of achieving the mission requirements. This research is designed to analyze the design and manufacturing of a wing based off the Manduca Sexta.

Inaccuracies in the fiber orientation can result in substantial changes in the material properties. Experimental vibration data of composite material samples manufactured using a three-ply [0/90/0] small non-homogenous fiber composite provided …

Accurate Dynamic Response Predictions Of Pnpsat I, Michael D. Trottier

Theses and Dissertations

Researchers at the Air Force Institute of Technology (AFIT) and the Operationally Responsive Space (ORS) Office have conducted extensive vibration testing and structural modeling on the first ORS Plug-and-Play Satellite (PnPSAT I). The intent of this research effort is to evaluate the premise that current post-integration spacecraft environmental test requirements can be reduced or modified using accurately tuned finite element (FE) models. As part of this research, modal testing was conducted on the PnPSAT I structural panels at AFIT. The modal testing was part of a much larger series of experimental trials on various configurations of PnPSAT I at the …

Finite Element Model Optimization Of The Falconsat-5 Structural Engineering Model, Cole C. Doupe

Theses and Dissertations

Space launch vehicles produce tremendously harsh environments for their payloads. One of the worst contributors to this harsh environment is vibration. Launch vehicle contractors require accurate dynamic models in order to perform coupled loads analyses with each payload to mitigate risks. Accurate predictions of the dynamic response of the payload are not achieved easily. The Finite Element (FE) method has proven to be the best approach in creating accurate dynamic models of complex structures. To improve the agreement between an FE model and the structure it represents, a common practice is to `tune' or adjust parameters of the FE model …

A Finite Element Evaluation Of An Experiment Related To Coating Damping Properties, Armando Deleon

Theses and Dissertations

Typically turbine engine blades gain protection from thermal damage by the use of hard coatings, such as magnesium aluminate spinel. Known as Thermal Barrier Coatings (TBC's), they have material properties that include several nonlinearities. These TBC's create damping primarily due to their nonlinear dissipation of energy. In order to effectively represent their damping properties, it is necessary to create a method which combines experimentation and analysis. Previous work has shown the need for a beam bounded and loaded in such a fashion that external support energy dissipation functions i.e. boundary conditions and aerodynamics are eliminated. Thus, a new experimental apparatus …

Flexible Twist For Pitch Control In A High Altitude Long Endurance Aircraft With Nonlinear Response, Vanessa L. Bond

Theses and Dissertations

Information dominance is the key motivator for employing high-altitude long-endurance (HALE) aircraft to provide continuous coverage in the theaters of operation. A joined-wing configuration of such a craft gives the advantage of a platform for higher resolution sensors. Design challenges emerge with structural flexibility that arise from a long-endurance aircraft design. The goal was to demonstrate that scaling the nonlinear response of a full-scale finite element model of a high-altitude long-endurance (HALE) aircraft was possible if the model was aeroelastically and "nonlinearly" scaled. A straight-forward method of scaling the first three natural vibration frequencies and mode shapes, and the first …

Nonlinear Flutter Analysis Of Curved Panels Under Yawed Supersonic Flow And At Elevated Temperatures Using Finite Elements, Satyajit Sudhir Ghoman

Mechanical & Aerospace Engineering Theses & Dissertations

There are large number of papers dedicated toward the investigation of flutter analysis of flat plates in supersonic flow regime, but very few papers address the problem of flutter of curved panels. Furthermore, many of the panel flutter investigations including thermal effects, have dealt with liat plates. Scarce literature exists regarding the flutter of curved panels with thermal effects. Hence, the objective of this thesis is to develop, for the first time in the literature, a consistent finite element formulation and an efficient solution procedure to investigate nonlinear flutter of curved panels at yawed supersonic flow at elevated temperatures.

Panel …