Mechanical Engineering Commons^™

Numerical Analysis Of A Roadway Piezoelectric Harvesting System, Abdul Rahman Badawi

Mechanical & Aerospace Engineering Theses & Dissertations

Highways, streets, bridges, and sidewalks with heavy traffic dissipate a considerable amount of waste mechanical energy every day. Piezoelectric energy harvesting devices are a very promising technology that can convert the waste mechanical energy to clean and renewable energy to enhance the sustainability of infrastructures. Research efforts in large-scale energy harvesting have led to the advancement of piezoelectric devices to the point that large-scale implementation is starting to become more feasible. The energy harvested by these devices can be used in many ways such as providing heating or cooling, melting ice, monitoring structural conditions in bridges and tunnels, and powering …

Parametric Study Of Residual Stresses In Wire And Arc Additive Manufactured Parts, Hisham Khaled Jamil Abusalma

Mechanical & Aerospace Engineering Theses & Dissertations

Wire and Arc Additive Manufacturing (WAAM) is a cost-effective additive manufacturing process due to its capability to fabricate large metal parts with high deposition rate and low equipment cost. Although this method is gaining popularity in manufacturing industry, more research is needed to understand process parameters’ effects on residual stress (RS) distribution and part distortion. As such, a 3D thermo-elastic-plastic transient model was established in ABAQUS and employed to investigate the effect of process parameters such as the torch speed, the deposition power and the interlayer dwell time on RS distribution and distortion in WAAM part. The numerical model utilized …

A Parametric Analysis Of A Turbofan Engine With An Auxiliary Bypass Combustion Chamber – The Turboaux Engine, Kaleab Fetahi

Mechanical & Aerospace Engineering Theses & Dissertations

A parametric study of a novel turbofan engine with an auxiliary combustion chamber, nicknamed the TurboAux engine is presented. The TurboAux engine is conceived as an extension of a low-bypass turbofan engine with an auxiliary bypass annular combustion chamber around the core stream. The study presented in this thesis is motivated by the need to facilitate clean secondary burning of fuel at temperatures higher than conventionally realized, from air exiting the low-pressure compressor. The parametric study starts by analyzing the turbojet engine and its performance with and without an afterburner segment attached. Following that, the conventional turbofan and its mixing …

The Effect Of Compaction Temperature And Pressure On Mechanical Properties Of 3d Printed Short Glass Fiber Composites, Pushpashree Jain Ajith Kumar Jain

Mechanical & Aerospace Engineering Theses & Dissertations

Among many thermoplastics that are used in engineering, polyamide 6 (nylon 6) is an extremely versatile engineering thermoplastic. Nylon filled with glass fibers has higher mechanical strength and high wear resistance than general purpose nylon. 3D printed composites, based on fused filament modeling, typically suffer from poor bead-to-bead bonding and relatively high void content, limiting their mechanical properties

This thesis explores the effect of compaction pressure and temperature on improving the mechanical properties of 3D printed composites. Engineering moduli in the printing and transverse to printing direction, as well as ultimate strength were measured using the tensile testing with Digital …

Conical Orbital Mechanics: A Rework Of Classic Orbit Transfer Mechanics, Cian Anthony Branco

Mechanical & Aerospace Engineering Theses & Dissertations

Simple orbital maneuvers obeying Kepler’s Laws, when taken with respect to Newton’s framework, require considerable time and effort to interpret and understand. Instead of a purely mathematical approach relying on the governing relations, a graphical geometric conceptual representation provides a useful alternative to the physical realities of orbits. Conic sections utilized within the full scope of a modified cone (frustum) were employed to demonstrate and develop a geometric approach to elliptical orbit transformations. The geometric model in-question utilizes the rotation of a plane intersecting the orbital frustum at some angle β (and the change in this angle) in a novel …

Detailed Modeling Of The Flash Hydrolysis Of Algae For Biofuel-Production In Comsol Multiphysics, Noah Joseph Legrand

Mechanical & Aerospace Engineering Theses & Dissertations

Algae-derived biofuels are being commercialized as an important renewable energy source. Like any new technology, conversion improvements are desired, including reductions in process complexity and better utilization of the entire microalgae feedstock. The Old Dominion Biomass Laboratory has focused on flash hydrolysis for algae biofuel production. That process involves rapidly heating algae and water mixed as a slurry to a subcritical state. Results from small-scale bench tests are promising, but process scale up is a challenge. Currently there exists a pilot laboratory scale system utilizing induction heating in order to reach controlled reaction temperatures with a reaction duration of 10 …

Model Based Systems Engineering For A Venture Class Launch Facility, Walter Mcgee Taraila

Mechanical & Aerospace Engineering Theses & Dissertations

A study of Model-Based Systems Engineering (MBSE) applied to a small-lift launch facility is presented. The research uses Systems Modeling Language (SysML) products and functional diagrams to document the structure, controls, electrical power, hydraulic, safety mechanisms, software, and fluid ground systems on a launch pad. The research is motivated by the need to design complex systems with an unambiguous understanding that improves communication, quality, productivity, and reduces risk. A model is developed following the ISO/IEC-15288 technical process framework. The stakeholder requirements are defined and analyzed to provide traceability to individual systems and subsystems. An architectural design is realized and implemented …

Finite Element Analysis Investigation Of Hybrid Thin-Ply Composites For Improved Performance Of Aerospace Structures, Alana M. Zahn

Mechanical & Aerospace Engineering Theses & Dissertations

Commercial and private aircraft have a need for strong yet light materials in order to have the most ideal performance possible. This study looks at the use of thin-ply composite materials to improve the performance of aircraft structures by means of weight savings and/or strength increase when compared to laminates that are composed of exclusively standard-ply materials. In order to perform an investigation based solely on finite element analysis, validation efforts were performed using test data from open hole tension, open hole compression, notched tension, and notched compression specimens. Once the models were validated sufficiently, the same modeling practices were …

Energy Harvesting Using Flextensional Piezoelectric Energy Harvesters In Resonance And Off-Resonance Modes, Mohamed A. Shabara

Mechanical & Aerospace Engineering Theses & Dissertations

Energy harvesting technologies are integrated into various modern devices and systems. These systems include Artificial Intelligence (AI) systems, Internet of Things (IoT), various types of energy harvesters are integrated in many engineering applications such as automotive, aerospace and ocean engineering. In order to develop a fully functioning stand-alone system, it is essential to integrate it with a built in power source such as a battery or a power generator. Also, in many situations, city power sources might not be available. Therefore, reliable, renewable and sustainable local power generators are desired. Piezoelectric energy harvesting (PEH) technologies, which are piezoelectric material-based devices, …

Mechanism Of Compaction With Wrinkle Formation During Automatic Stitching Of Dry Fabrics And The Size Effect Of Compression Molded Discontinuous Fiber-Reinforced Composites, Anibal Benjamin Beltran Laredo

Mechanical & Aerospace Engineering Theses & Dissertations

With an ever-increasing demand for composites, more ways of manufacturing them are becoming popular and widely used. Stitching of dry fabrics is an efficient method for improving delamination resistance. Discontinuous fiber reinforced composites can be used as a lightweight alternative material for metals through a process of compression molding, which allows for complex shape manufacturing while offering structural grade mechanical properties.

This study demonstrates how the stitching of dry fabrics can be adapted to more complex surfaces. The consequences of stitching of curvilinear surfaces can result in defect formation. Therefore, to understand the physical formation of possible defects, experimental characterization …

A Study Of The Aeroacoustics Of Swept Propellers For Small Unmanned Aerial Vehicles, Arthur David Wiedemann

Mechanical & Aerospace Engineering Theses & Dissertations

In recent years, small unmanned aerial vehicles (UAVs) have increased in availability and use in both public and commercial sectors. This increased use of small UAVs or “drones” has the unfortunate consequence of introducing excessive noise into communities where they operate. Implementation of noise reduction methods is necessary if we wish to see expanded use of drones in public areas. With electric propulsion, the primary source of noise is the rotor/propeller used in contemporary multi-rotor configurations. In this thesis, the aerodynamics and acoustic behavior of various swept propellers is examined with computational and experimental methods.

A family of propeller geometries …

Role Of Anisometric Particles In Ice-Templated Porous Ceramic Structure And Mechanical Properties, Mahesh Banda

Mechanical & Aerospace Engineering Theses & Dissertations

Open-cell macroporous ceramics have a significant impact on advancing various engineering endeavors such as bone-tissue engineering, lithium-ion batteries, filtration, thermal insulation, impact protection, etc. While pore orientation in conventional open-cell foams is random, in recent years, significant interest has grown in utilizing directionally porous ceramics in these applications to enhance performance. Ice-templating has emerged as a versatile technique that can synthesize directionally macroporous ceramics with low pore tortuosity. Although the fabrication is relatively straightforward, the challenge is that there are numerous variables associated with this technique, which can have significant effects on the final structure and macroscopic properties. As a …

Through-Thickness Reinforcement And Repair Of Carbon Fiber Based Honeycomb Structures Under Flexure And Tension Of Adhesively Bonded Joints, Aleric Alden Sanders

Mechanical & Aerospace Engineering Theses & Dissertations

Repair and reinforcement of composite honeycomb structures is an area of concern as higher demands are being placed on high strength, lightweight structural materials, such as carbon fiber reinforced plastics and corresponding honeycomb structures. A common issue with these structures is when a delamination in the facesheet may form and spread, leading to a failure scenario. An investigation of adding a through thickness reinforcement (TTR) to these structures at the sample level that undergo four-point-bending, tension, and joining methods is conducted throughout this thesis. The embedding of pultruded carbon fiber rods is found to be an ideal addition to composite …

Thermal Contact Resistance Measurement And Related Uncertainties, Amanda Elizabeth Stark

Mechanical & Aerospace Engineering Theses & Dissertations

Thermal contact resistance is an important parameter in detailed thermal analysis and design of aerospace systems. The ability to determine thermal contact resistance reliably can have a significant impact on the fidelity of thermal models—particularly for space applications. The 2004 NASA Langley Research Center thermal contact resistance test apparatus has been employed to evaluate two methods for inferring estimated interface surface temperatures so that thermal contact resistance can be calculated more accurately. The traditional method of extrapolation is a steady-state approach, while the new method utilizes inverse heat transfer techniques to account for inherent unsteadiness in these quasi-steady-state measurements. The …

Compaction And Residual Stress Modeling In Composite Manufactured With Automated Fiber Placement, Von Clyde Jamora

Mechanical & Aerospace Engineering Theses & Dissertations

Automated fiber placement is a state-of-the-art manufacturing process that allows for complex layup patterns and can quickly place, cut, and restart composite tows. However, with this type of manufacturing process layup defects are inevitable, and manufacturing defects propagate after curing. Process modeling is the considered approach for exploring the defect prediction. Two different but related works were conducted, which are the thermochemical and hyperelastic model and the residual deformation model. For the model before cooling, a hyperelastic model and a thermo-chemical were made to simulate the compaction and heat transfer. Temperature dependent properties that are a function of degree of …