Engineering Commons^™

Post-Processing And Characterization Of Additive Manufactured Carbon Fiber Reinforced Semi-Crystalline Polymers, Patricia Revolinsky

Mechanical & Aerospace Engineering Theses & Dissertations

The aim of this work is to study the effect of post-processing on additive manufactured (AM) continuous carbon fiber reinforced plastics (CFRPs) performance. As-printed AM CFRPs do not perform as well as conventionally manufactured CFRPs with the same composition. Possible improvements to AM CFRP performance include annealing and applying uniaxial pressure with elevated temperature. Samples were subjected to pressure and temperature treatments and annealing at a constant temperature. Treated materials were subjected to three-point bending tests, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and scanning electron microscopy (SEM) to characterize and assess sample performance. Results were assessed for flexural strength, …

Tunable Compressive Mechanical Behavior Of Ice-Templated Materials, Sashanka Akurati

Mechanical & Aerospace Engineering Theses & Dissertations

The inherent hierarchical microstructural organization in natural materials is responsible for their excellent mechanical properties beyond that predicted by the simple rule-of-mixtures. Further exhibit synergy between strength and toughness, otherwise mutually exclusive in brittle materials. Conventional processing methods are unable to replicate hierarchical microstructures in engineering ceramics akin to that observed in natural materials. Ice-templating has emerged as a potential technique to fabricate bioinspired hierarchical materials. This process involves simultaneous unidirectional solidification and phase segregation of aqueous suspensions. Ice-templated porous ceramic materials have received significant attention for overcoming several limitations of conventional ceramic foams currently used in numerous engineering applications. …

The Influence Of Participation In A Multi-Disciplinary Collaborative Service Learning Project On The Effectiveness Of Team Members In A 100-Level Mechanical Engineering Class, Stacie I. Ringleb, Pilar Pazos, Julia Noginova, Francisco Cima, Orlando Ayala, Krishnanand Kaipa, Jennifer Kidd, Kristie Gutierrez

Mechanical & Aerospace Engineering Faculty Publications

Engineers need to develop professional skills, including the ability to work successfully in teams and to communicate within and outside of their discipline, in addition to required technical skills. A collaborative multi-disciplinary service learning project referred to as Ed+gineering was implemented in a 100-level mechanical engineering course. In this collaboration, mechanical engineering students, primarily in the second semester of their freshman year or first semester of their second year, worked over the course of a semester with education students taking a foundations course to develop and deliver engineering lessons to fourth or fifth graders. Students in comparison engineering classes worked …

Analysis Of A Non-Equilibrium Vortex Pair As Aircraft Trailing Vortices, Manuel Ayala

Mechanical & Aerospace Engineering Theses & Dissertations

Shortly after the roll-up evolution of the vortex sheet behind the wings of an aircraft, a coherent counter-rotating vortex pair emerges. Presence of this vortex pair in the downstream of an aircraft, creates unsafe conditions for other aircraft, especially near airport runways. Fundamental knowledge of the physics that govern the formation, duration and dissipation of aircraft wake vortices is desirable in order to improve aircraft operational safety. This study uses non-equilibrium pressure theory to develop an accurate model describing the physical behavior of the vortex pair created by an aircraft in the early to mid-field vortex regime. An isolated aircraft …

Modeling Interactions In Concentrated Ceramic Suspensions Under Ac Electric Field, Naga Bharath Gundrati

Mechanical & Aerospace Engineering Theses & Dissertations

Colloidal processing of ceramics manipulates the interaction forces using additives or external energy field between the suspending particles to fabricate complex structures. Under AC electric field, mutual dielectrophoretic (DEP) forces between particles create particle chaining. Dielectrophoresis (DEP) is adopted to control ceramic particles in the colloidal suspension, which can benefit from employing DEP forces to externally control the fabrication of ceramic materials with desired porosity and hierarchical structure. To this end, it is crucial to understand the interactions between ceramic particles in aqueous media and AC electric field. The dynamic interactions of ceramic particles under AC electric field are modelled …

Development And Applications Of Adjoint-Based Aerodynamic And Aeroacoustic Multidisciplinary Optimization For Rotorcraft, Ramiz Omur Icke

Mechanical & Aerospace Engineering Theses & Dissertations

Urban Air Mobility (UAM) is one of the most popular proposed solutions for alleviating traffic problems in populated areas. In this context, the proposed types of vehicles mainly consist of rotors and propellers powered by electric motors. However, those rotary-wing components can contribute excessively to noise generation. Therefore, a significant noise concern emerges due to urban air vehicles in or around residential areas. Reducing noise emitted by air vehicles is critically important to improve public acceptance of such vehicles for operations in densely populated areas.

Two main objectives of the present dissertation are: (1) to expand the multidisciplinary optimization to …

The Effect Of Through Thickness Reinforcement On Debonding Behavior Of Skin/Stringer Configuration, Yogaraja Sridhar

Mechanical & Aerospace Engineering Theses & Dissertations

Investigation of this study is to the determine the crack propagation and disbonding in the bonded region of the skin and stringer specimen. An adhesive layer has been used to bond the skin and stringer by using a heat press operation. After the bonding, a drilling method has been adopted to install the through thickness reinforcement in the specimen. The key role of the through thickness reinforcement is to increase the stiffness and strength of the panels and to prevent the crack propagation or disbonding of the panels. The reinforcement was installed in pure (Pristine) samples and in defect samples …

Gradient-Based Tradeoff Design For Engineering Applications, Lena Alexis Royster

Mechanical & Aerospace Engineering Theses & Dissertations

This research presents a formal method for gradient based tradeoff design including methods that extend to cases with singularities and cases with more performance characteristics then design variables. The goal is to find revised design variables that can achieve the targeted performance characteristics and remove any violations to the constraint functions. The tradeoff design problem is formulation in the framework of the Sequential Quadratic Programming and is solved using the gradient based method. The optimal solution is the search direction, s, which represents the most effective way to reduce the current objective and correct the current violation. In this research …

A Model-Based Systems Engineering Approach To E-Vtol Aircraft And Airspace Infrastructure Design For Urban Air Mobility, Heidi Selina Glaudel

Mechanical & Aerospace Engineering Theses & Dissertations

This paper serves to contribute to Model-Based Systems Engineering (MBSE) by following the NASA Systems Engineering Handbook framework for a Systems Engineering (SE) design approach to an Electric Vertical Takeoff and Landing (e-VTOL) aircraft and the incorporating airspace infrastructure. The focus of this study is, by using the MBSE model created, to capture the technical requirements definition and design intent of the vehicle and airspace inclusive of community specific knowledge derived from the Federal Aviation Administration (FAA) NextGen Urban Air Mobility (UAM) Concept of Operations (ConOps) version 1.0. The stakeholder requirements derived from the FAA UAM NextGen ConOps will form …

Improved Strain Gage Instrumentation Strategies For Rotorcraft Blade Measurements, Timothy S. Davis

Mechanical & Aerospace Engineering Theses & Dissertations

In this work, a new strategy is presented to wire, calibrate, and measure strain gages for rotor blade testing that will provide more information and is robust to individual gage loss. The additional information can be used in several ways. including reducing redundancy, offering rapid identification of damage locations, and in some cases reducing risk allowing tests to continue to collect calibrated data after one or more sensors have failed. This strategy replaces the classical four-gage full Wheatstone bridge with four separately wired quarter bridges that are combined into a full bridge in the data acquisition system using a calculated …

Drive Leg And Stride Leg Ground Reaction Forces Relationship To Medial Elbow Stress And Velocity In Collegiate Baseball Pitchers, Brett Smith

Biomedical Engineering Theses & Dissertations

This study examines several different kinetic variables in relation to pitch velocity and elbow varus torque in collegiate baseball pitchers using force plates, an inertial measurement unit, and a radar unit. The purpose of this study is to investigate the kinetic variables being measured and their relationship to pitch velocity and loads being placed on the medial elbow. Twelve collegiate baseball pitchers participated in this study, which was approved by the IRB. Impulse of the drive leg in the anterior-posterior direction, stride leg peak force in the anterior-posterior (AP) direction, elbow varus torque, and pitch velocity were all measured. Two …

Mechanism For The Unfolding Of The Top7 Protein In Steered Molecular Dynamics Simulations As Revealed By Mutual Information Analysis, Ognjen Perišić, Willy Wriggers

Mechanical & Aerospace Engineering Faculty Publications

We employed mutual information (MI) analysis to detect motions affecting the mechanical resistance of the human-engineered protein Top7. The results are based on the MI analysis of pair contact correlations measured in steered molecular dynamics (SMD) trajectories and their statistical dependence on global unfolding. This study is the first application of the MI analysis to SMD forced unfolding, and we furnish specific SMD recommendations for the utility of parameters and options in the TimeScapes package. The MI analysis provided a global overview of the effect of perturbation on the stability of the protein. We also employed a more conventional trajectory …

Electroosmotic Flow Of Viscoelastic Fluid Through A Constriction Microchannel, Jianyu Ji, Shizhi Qian, Zhaohui Liu

Mechanical & Aerospace Engineering Faculty Publications

Electroosmotic flow (EOF) has been widely used in various biochemical microfluidic applications, many of which use viscoelastic non-Newtonian fluid. This study numerically investigates the EOF of viscoelastic fluid through a 10:1 constriction microfluidic channel connecting two reservoirs on either side. The flow is modelled by the Oldroyd-B (OB) model coupled with the Poisson–Boltzmann model. EOF of polyacrylamide (PAA) solution is studied as a function of the PAA concentration and the applied electric field. In contrast to steady EOF of Newtonian fluid, the EOF of PAA solution becomes unstable when the applied electric field (PAA concentration) exceeds a critical value for …

Opportunistic Maintenance Strategy Of A Heave Compensation System For Expected Performance Degradation, Chao Zhang, Yujie Qian, Hongyan Dui, Shaoping Wang, Rentong Chen, Mileta M. Tomovic

Engineering Technology Faculty Publications

In the marine industry, heave compensation systems are applied to marine equipment to compensate for the adverse effects of waves and the hydraulic system is usually used as the power system of heave compensation systems. This article introduces importance theory to the opportunistic maintenance (OM) strategy to provide guidance for the maintenance of heave compensation systems. The working principle of a semi-active heave compensation system and the specific working states of its hydraulic components are also first explained. Opportunistic maintenance is applied to the semi-active heave compensation system. Moreover, the joint integrated importance measure (JIIM) between different components at different …

Fluid-Wall Interactions In Pseudopotential Lattice Boltzmann Models, Cheng Peng, Luis F. Ayala, Orlando M. Ayala

Engineering Technology Faculty Publications

Designing proper fluid-wall interaction forces to achieve proper wetting conditions is an important area of interest in pseudopotential lattice Boltzmann models. In this paper, we propose a modified fluid-wall interaction force that applies for pseudopotential models of both single-component fluids and partially miscible multicomponent fluids, such as hydrocarbon mixtures. A reliable correlation that predicts the resulting liquid contact angle on a flat solid surface is also proposed. This correlation works well over a wide variety of pseudopotential lattice Boltzmann models and thermodynamic conditions.

Non-Equilibrium Behavior Of Large-Scale Axial Vortex Cores, Robert L. Ash, Irfan R. Zardadkhan

Mechanical & Aerospace Engineering Faculty Publications

A logical basis for incorporating pressure non-equilibrium and turbulent eddy viscosity in an incompressible vortex model is presented. The infrasonic acoustic source implied in our earlier work has been examined. Finally, this non-equilibrium turbulent vortex core is shown to dissipate mechanical energy more slowly than a Burgers vortex, helping us to explain the persistence of axial vortices in nature. Recent molecular dynamics simulations replicate aspects of this non-equilibrium pressure behavior.

Evaluation Of Murrell’S Ekf-Based Attitude Estimation Algorithm For Exploiting Multiple Attitude Sensor Configurations, Sharanabasaweshwara Asundi, Norman Fitz-Coy, Haniph Latchman

Mechanical & Aerospace Engineering Faculty Publications

Pico- and nano-satellites, due to their form factor and size, are limited in accommodating multiple or redundant attitude sensors. For such satellites, Murrell's implementation of the extended Kalman filter (EKF) can be exploited to accommodate multiple sensor configurations from a set of non redundant attitude sensors. The paper describes such an implementation involving a sun sensor suite and a magnetometer as attitude sensors. The implementation exploits Murrell's EKF to enable three sensor configurations, which can be operationally commanded, for satellite attitude estimation. Among the three attitude estimation schemes, (i) sun sensor suite and magnetometer, (ii) magnetic field vector and its …

One-Dimensional Lateral Force Anisotropy At The Atomic Scale In Sliding Single Molecules On A Surface, Yuan Zhang, Daniel J. Trainer, Badri Narayanan, Yang Li, Anh T. Ngo, Sushila Khadka, Arnab Neogi, Brandon Fisher, Larry A. Curtiss, Subramanian K.R.S. Sankaranarayanan, Saw Wai Hla

Physics Faculty Publications

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations. We also demonstrate that …

Pore Microstructure Impacts On Lithium Ion Transport And Rate Capability Of Thick Sintered Electrodes, Ziyang Nie, Rohan Parai, Chen Cai, Charles Michaelis, Jacob M. Lamanna, Daniel S. Hussey, David L. Jacobson, Dipankar Ghosh, Gary M. Koenig Jr.

Mechanical & Aerospace Engineering Faculty Publications

Increasing electrode thickness is one route to improve the energy density of lithium-ion battery cells. However, restricted Li⁺ transport in the electrolyte phase through the porous microstructure of thick electrodes limits the ability to achieve high current densities and rates of charge/discharge with these high energy cells. In this work, processing routes to mitigate transport restrictions were pursued. The electrodes used were comprised of only active material sintered together into a porous pellet. For one of the electrodes, comparisons were done between using ice-templating to provide directional porosity and using sacrificial particles during processing to match the geometric density …

Generic Design Methodology For Smart Manufacturing Systems From A Practical Perspective, Part I—Digital Triad Concept And Its Application As A System Reference Model, Zhuming Bi, Wen-Jun Zhang, Chong Wu, Chaomin Luo, Lida Xu

Information Technology & Decision Sciences Faculty Publications

Rapidly developed information technologies (IT) have continuously empowered manufacturing systems and accelerated the evolution of manufacturing system paradigms, and smart manufacturing (SM) has become one of the most promising paradigms. The study of SM has attracted a great deal of attention for researchers in academia and practitioners in industry. However, an obvious fact is that people with different backgrounds have different expectations for SM, and this has led to high diversity, ambiguity, and inconsistency in terms of definitions, reference models, performance matrices, and system design methodologies. It has been found that the state of the art SM research is limited …

Generic Design Methodology For Smart Manufacturing Systems From A Practical Perspective. Part Ii—Systematic Designs Of Smart Manufacturing Systems, Zhuming Bi, Wen-Jun Zhang, Chong Wu, Chaomin Luo, Lida Xu

Information Technology & Decision Sciences Faculty Publications

In a traditional system paradigm, an enterprise reference model provides the guide for practitioners to select manufacturing elements, configure elements into a manufacturing system, and model system options for evaluation and comparison of system solutions against given performance metrics. However, a smart manufacturing system aims to reconfigure different systems in achieving high-level smartness in its system lifecycle; moreover, each smart system is customized in terms of the constraints of manufacturing resources and the prioritized performance metrics to achieve system smartness. Few works were found on the development of systematic methodologies for the design of smart manufacturing systems. The novel contributions …

Development And Characterization Of Nb₃N/Al₂0₃ Superconducting Multilayers For Particle Accelerators, Chris Sundahl, Junki Makita, Paul B. Welander, Yi-Feng Su, Fumitake Kametani, Lin Xie, Huimin Zhang, Lian Li, Alex Gurevich, Chang-Beom Eom

Physics Faculty Publications

Superconducting radio-frequency (SRF) resonator cavities provide extremely high quality factors > 10¹⁰ at 1-2 GHz and 2 K in large linear accelerators of high-energy particles. The maximum accelerating field of SRF cavities is limited by penetration of vortices into the superconductor. Present state-of-the-art Nb cavities can withstand up to 50 MV/m accelerating gradients and magnetic fields of 200-240 mT which destroy the low-dissipative Meissner state. Achieving higher accelerating gradients requires superconductors with higher thermodynamic critical fields, of which Nb₃Sn has emerged as a leading material for the next generation accelerators. To overcome the problem of low vortex penetration …

Development Of An Undergraduate Welding Laboratory For Research And Education, Hamid Eisazadeh, Alok K. Verma

Engineering Technology Faculty Publications

The shortage of welders in Hampton Roads area, where many shipyards are located, is becoming severe for shipbuilding in coming years. Many welding engineers graduated from universities located out of state, tend to go back to companies near their home, after receiving couple years of welding experience at Hampton Roads shipyards. Therefore, it is critical to train local welders. In order to address the welding workforce needs of Hampton Roads, the Department of Engineering Technology at Old Dominion University has recently launched an initiative for developing a laboratory for welding processes (LWP) for supporting educational and research activities in its …