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Full-Text Articles in Engineering
Dynamic Triaxial Compression Experiments On Borosilicate And Soda-Lime Glass, John T. Chojnacki
Dynamic Triaxial Compression Experiments On Borosilicate And Soda-Lime Glass, John T. Chojnacki
Open Access Theses
A series of compression experiments were performed on borosilicate and soda-lime glass using a triaxial compression Kolsky bar. The triaxial compression Kolsky bar differs from a traditional Kolsky bar by having two pressure chambers, one enclosing the specimen and the other enclosing the end of the transmission bar, so that a specimen may be pre-stressed axially and radially before a dynamic axial load is applied. The result is a modified Kolsky bar capable of measuring axial deformation and axial stresses of a specimen at various strain rates under a range of confinement pressures. Borosilicate glass was subjected to triaxial confinement …
Loss Of Accuracy Using Smeared Properties In Composite Beam Modeling, Ning Liu
Loss Of Accuracy Using Smeared Properties In Composite Beam Modeling, Ning Liu
Open Access Theses
Advanced composite materials have broad, proven applications in many engineering systems ranging from sports equipment sectors to components on the space shuttle because of their lightweight characteristics and significantly high stiffness. Together with this merit of composite materials is the challenge of improving computational simulation process for composites analysis. Composite structures, particularly composite laminates, usually consist of many layers with different lay-up angles. The anisotropic and heterogeneous features render 3D finite element analysis (FEA) computationally expensive in terms of the computational time and the computing power. ^ At the constituent level, composite materials are heterogeneous. But quite often one homogenizes …
Comprehensively Simulating The Mixed-Mode Progressive Delamination In Composite Laminates, Zhenyuan Gao
Comprehensively Simulating The Mixed-Mode Progressive Delamination In Composite Laminates, Zhenyuan Gao
Open Access Theses
Delamination, or interlaminar debonding, is a commonly observed failure mechanism in composite laminates. It is of great significance to comprehensively simulate the mixed-mode progressive delamination in composite structures because by doing this, people can save a lot of effort in evaluating the safe load which a composite structure can endure.^ The objective of this thesis is to develop a numerical approach to simulating double-cantilever beam (DCB) and mixed-mode bending (MMB) tests and also of specifying/validating various cohesive models. A finite element framework, which consists of properly selecting time integration scheme (explicit dynamic), viscosity, load rate and mass scaling, is developed …
Performance Analysis Of Vortex Based Mixers For Confined Flows, Timo Buschhagen
Performance Analysis Of Vortex Based Mixers For Confined Flows, Timo Buschhagen
Open Access Theses
The hybrid rocket is still sparsely employed within major space or defense projects due to their relatively poor combustion efficiency and low fuel grain regression rate. Although hybrid rockets can claim advantages in safety, environmental and performance aspects against established solid and liquid propellant systems, the boundary layer combustion process and the diffusion based mixing within a hybrid rocket grain port leaves the core flow unmixed and limits the system performance. One principle used to enhance the mixing of gaseous flows is to induce streamwise vorticity. The counter-rotating vortex pair (CVP) mixer utilizes this principle and introduces two vortices into …
Flexible Weapons Architecture Design, William C. Pyant
Flexible Weapons Architecture Design, William C. Pyant
Open Access Theses
Present day air-delivered weapons are of a closed architecture, with little to no ability to tailor the weapon for the individual engagement. The closed architectures require weaponeers to make the target fit the weapon instead of fitting the individual weapons to a target. The concept of a flexible weapons aims to modularize weapons design using an open architecture shell into which different modules are inserted to achieve the desired target fractional damage while reducing cost and civilian casualties. This thesis shows that the architecture design factors of damage mechanism, fusing, weapons weight, guidance, and propulsion are significant in enhancing weapon …
Ads-B Used In Improvement Of Air Traffic Control, Hao Wang
Ads-B Used In Improvement Of Air Traffic Control, Hao Wang
Open Access Theses
Automatic dependent surveillance – broadcast (ADS-B) is a central component of the NextGen air traffic control program. This surveillance technology can replace current secondary surveillance radars (SSR) and improve cockpit situational awareness. The service can improve traffic surveillance capabilities by sharing accurate aircraft position information between pilots and air traffic controllers. In addition, ADS-B provides pilots with weather as well as air traffic information for nearby area. In order to receive these traffic and weather services, a pilot must have appropriate onboard equipment including GPS receiver, Universal Access Transceiver, antenna and multi-function cockpit display which is capable of receiving and …
Linear Matrix Inequality-Based Nonlinear Adaptive Robust Control With Application To Unmanned Aircraft Systems, David William Kun
Linear Matrix Inequality-Based Nonlinear Adaptive Robust Control With Application To Unmanned Aircraft Systems, David William Kun
Open Access Theses
Unmanned aircraft systems (UASs) are gaining popularity in civil and commercial applications as their lightweight on-board computers become more powerful and affordable, their power storage devices improve, and the Federal Aviation Administration addresses the legal and safety concerns of integrating UASs in the national airspace. Consequently, many researchers are pursuing novel methods to control UASs in order to improve their capabilities, dependability, and safety assurance. The nonlinear control approach is a common choice as it offers several benefits for these highly nonlinear aerospace systems (e.g., the quadrotor). First, the controller design is physically intuitive and is derived from well known …
Real-Time Rss-Based Indoor Navigation For Autonomous Uav Flight, Sangjun Lee
Real-Time Rss-Based Indoor Navigation For Autonomous Uav Flight, Sangjun Lee
Open Access Theses
Navigation for the autonomous flight of Unmanned Aerial Vehicles (UAVs) in an indoor space has attracted much attention recently. One of the main goals of an indoor navigation system is developing an alternative method to obtain position information that can replace or complement the global positioning system. While much research has focused on vision-based indoor navigation systems, this paper aims to develop a Received Signal Strength (RSS)-based navigation system, which is a more cost effective alternative. Then, the position and attitude of a UAV can be computed by the fusion of RSS measurements and measurements from the onboard inertial measurement …
Air Traffic Management Under Uncertain Weather Impact, Le Gao
Air Traffic Management Under Uncertain Weather Impact, Le Gao
Open Access Theses
Air traffic management under uncertain weather impact is a difficult problem. In this thesis, by dividing the whole air traffic systems into small cells, a new method using database to integrate weather and flight data is proposed. An algorithm has been developed to project weather data onto cells. This research also uses a predictive view to find ights which are affected by severe weather. And a prototype detour algorithm is applied on those flights based on the status information of each cell.
Considerations For Nondestructive Evaluation Of Discontinuous Fiber Composites Using Dynamic Analysis, Rebecca A. Cutting
Considerations For Nondestructive Evaluation Of Discontinuous Fiber Composites Using Dynamic Analysis, Rebecca A. Cutting
Open Access Theses
Knowledge of the composite microstructure is vital to predicting performance of the structural member. However, depending on the manufacturing process, the microstructure of the part may be unknown and not predictable with simulation software. A few non-destructive evaluation techniques have been adjusted to predict fiber orientation of composites, including CT scans and thermography, but none have proven acceptable on a large scale with the amount of fidelity required. This research investigated the use of dynamic analysis as a non-destructive evaluation technique to predict fiber orientation of discontinuous fiber compression molded parts. While the method is currently unable to predict individual …
Effect Of Electrode Geometry On High Energy Spark Discharges In Air, Mounia Belmouss
Effect Of Electrode Geometry On High Energy Spark Discharges In Air, Mounia Belmouss
Open Access Theses
The government, aerospace, and transportation industries are deeply invested in developing new technologies to improve the performance and maneuverability of current and future aircraft while reducing aerodynamic noise and environmental impact. One of the key pathways to meet these goals is through aerodynamic flow control, which can involve suppressing or inducing separation, transition and management of turbulence in boundary layers, increasing the lift and reducing the drag of airfoils, and gas mixing to control fluctuating forces and aerodynamic noise [1]. In this dissertation, the complex flow field following a spark discharge is studied for a range of geometries and discharge …
Asymptotic Modelling Of A Thermopiezoelastic Anisotropic Smart Plate, Yufei Long
Asymptotic Modelling Of A Thermopiezoelastic Anisotropic Smart Plate, Yufei Long
Open Access Theses
Motivated by the requirement of modelling for space flexible reflectors as well as other applications of plate structures in engineering, a general anisotropic laminated thin plate model and a monoclinic Reissner-Mindlin plate model with thermal deformation, two-way coupled piezoelectric effect and pyroelectric effect is constructed using the variational asymptotic method, without any ad hoc assumptions. Total potential energy contains strain energy, electric potential energy and energy caused by temperature change. Three-dimensional strain field is built based on the concept of warping function and decomposition of the rotation tensor. The feature of small thickness and large in-plane dimension of plate structure …
Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna
Delamination Of C/Pekk I-Beam Using Virtual Crack Closure Technique And Cohesive Zone Method, Greeshma Ramakrishna
Open Access Theses
A damage study is conducted on a carbon epoxy/PEKK (poly-ether-ketone-ketone) thermoplastic composite I-Beam, with a pre crack of 100 mm modeled between the top flange and the filler (butt joint between filler and web). This project is in collaboration with Fokker Aerostructures, Netherlands and is part of the Thermoplastic Primary Aircraft Structure innovation program (TAPAS). The C/PEKK I-Beam is modeled after a section of the Gulfstream G650 aircraft's centre beam, which was previously a carbon fiber/epoxy hat-stiffened skin construction. The objective of the thesis is to identify if the crack propagates in the I-Beam within the load range that act …
Dynamics Of Transitions Between Capillary Stable States Under Weightlessness, Praveen Srikanth
Dynamics Of Transitions Between Capillary Stable States Under Weightlessness, Praveen Srikanth
Open Access Theses
The study of two phase systems with one of the phases obstructing the other is of importance in a lot of fields. Liquid droplets in airways and air bubbles in the blood stream both fall under this category of problems. Helium bubbles in hydrazine fuel lines of satellites also have been found to cause frequent thruster shutdown and also seriously affect spacecraft control. Studies have been carried out until now to look at static equilibrium topologies and stability of such two phase systems in straight, bent and laterally compressed capillaries. In this investigation we look at the dynamics of the …