Mechanical Engineering Commons^™

Computational Dynamics For The Flexible Multi-Body System, Yu Liu

Mechanical & Aerospace Engineering Theses & Dissertations

Research in computational dynamics has tremendously developed in the recent years because of the demand for analysis and simulation of various multi-body systems in the growing bio-medical, mechanical and aerospace industries. These multi-body systems are made of individual bodies that are interconnected via mechanical joints. Mathematically, these joints that connect the bodies can be described as constraint equations imposed upon the motions of the involved free bodies. This process will result in an equation of motion expressed in the form of a differential-algebraic equation (DAE). This is one of the main difficulties when dealing with the multi-body system because these …

A Polymer-Based Microfluidic Device With Electrolyte-Enabled Distributed Transducers (Eedt) For Distributed Load Detection, Peng Cheng

Mechanical & Aerospace Engineering Theses & Dissertations

The capability of detecting distributed static and dynamic loads is indispensable in a wide variety of applications, such as examining anatomical structures of biological tissues in tissue health analysis and minimally invasive surgery (MIS) and determining the texture of an object in robotics. This dissertation presents a comprehensive study of a polymer-based microfluidic device with electrolyte-enabled distributed transducers and demonstrates a new concept on using a single microfluidic device for distributed-load detection, which takes advantage of the low-cost microfluidic fabrication technology and the low modulus and biocompatibility of polymer. The core of the device is a single deformable polymer microstructure …

The Influence Of Non-Equilibrium Pressure On Rotating Flows, Irfan Rashid Zardadkhan

Mechanical & Aerospace Engineering Theses & Dissertations

This study was undertaken to investigate the influence of pressure relaxation on steady, incompressible flows with strong streamline curvature. In the early part of this dissertation research, the significance of non-equilibrium pressure forces in controlling the structure of a steady, two dimensional axial vortex was demonstrated. In order to extend the study of pressure relaxation influences on more complex rotating flows, this dissertation has examined other rotating flow features that can be associated with hurricanes, tornadoes and dust devils. To model these flows, modified boundary layer equations were developed for a fluid column rotating near a solid plane including the …

Numerical Analysis And Design Optimization Of Organic Bulk Hetero-Junction Solar Cells Using The Mixed Finite Element And Arc-Length Methods, James L. Dean

Mechanical & Aerospace Engineering Theses & Dissertations

Due to the high coupling and non-linear nature of the semiconductor equations, numerical stability becomes a major problem when using a purely Newtonian numerical method in solving these equations. Presented is a robust mixed finite element formulation with application for organic solar cell devices that incorporates the arc-length predictor-corrector method to bypass such stability issues. The simulated device represents a multilayered solar cell using organic bulk hetero-junction materials including donor materials Poly[2,1,3-benzothiadiazole-4,7-diyl[4,4-bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4- b']dithiophene-2,6-diyl]] (PCPDTBT) and poly 3-hexylthiophene (P3HT) with acceptor fullerene materials [6,6]-phenyl C61 butyric acid methyl ester (PC61BM) or [6,6]-phenyl C71 butyric acid methyl ester (PC71BM) as the photoactive …

Modeling, Identification, Validation And Control Of A Hybrid Maglev Ball System, Ahmed Elhussein E. Mekky

Mechanical & Aerospace Engineering Theses & Dissertations

In this thesis, the electrodynamics of a single axis hybrid electromagnetic suspension Maglev system was modeled and validated by applying it to a single axis hybrid maglev ball experiment. By exploring its linearized model, it was shown that the single axis hybrid Maglev ball has inherently unstable dynamics. Three control scenarios were explored based on the linearized model; (1) Proportional, Deferential (PD) control, (2) Proportional, Deferential, Integral (PID) and (3) PID controller with pre-filtering. This thesis has shown that a PID controller with a pre-filtering technique can stabilize such a system and provide a well-controlled response.

A parametric system identification …

Evaluation Of Autonomous Robotic Milling Methodology For Natural Tooth-Shaped Implants Based On Sko Optimization, Yongki Yoon

Mechanical & Aerospace Engineering Theses & Dissertations

Robotic surgery is one of the most demanding and challenging applications in the field of automatic control. One of the conventional surgeries, the dental implantation, is the standard methodology to place the artificial tooth root composed of titanium material into the upper or lower jawbone. During the dental implant surgery, mechanical removal of the bone material is the most critical procedure because it may affect the patient's safety including damage to the mandibular canal nerve and/or piercing the maxillary sinus. With this problem, even though short term survival rates are greater than 95%, long term success rate of the surgery …

Dynamic Model Of Sailors Descending A Navy Ship Ladder, Jonathan Coulter

Mechanical & Aerospace Engineering Theses & Dissertations

Knee moments are greater in individuals who climb Navy ship ladders than in people climbing stairs. Because it is known that people who climb stairs frequently are at greater risk for osteoarthritis and that people in the Navy report higher incidences of knee pain, it was hypothesized that the internal joint reaction forces during the sailor's descent of a ship ladder would be greater than internal joint reaction forces of gait and stair climbing. Dimensions of a commonly used Navy ship ladder were collected and a replica was constructed. The replica was instrumented to collect 3D kinematics and kinetics during …

Analysis Of Bar Deformation Under Sternum Forces During Surgical Correction Of Pectus Excavatum In Children, Rohit N. Nikam

Mechanical & Aerospace Engineering Theses & Dissertations

Pectus excavatum (PE) also known as sunken or funnel chest is the most common chest wall deformity and affects 1 in every 1,000 children. In PE patients, the middle lower portion of the sternum is depressed producing concave appearance of the anterior part of the chest wall. This problem can be corrected with minimally invasive surgery developed by Dr. Donald Nuss in 1986. A specially made steel bar is implanted to lift the sternum to its normal position. This technique has been modified several times to improve safety and effectiveness of the bar placement and removal. One of the significant …

Kinematic Analysis Of Gesture In Aphasia, Haroon Osmanzada

Mechanical & Aerospace Engineering Theses & Dissertations

Individuals who have experienced a left hemispheric stroke often develop aphasia, which results in a loss of effective verbal communication and reliance on gesturing to communicate. In this study we combined these two aspects of aphasic word retrieval difficulties and gesturing with three-dimensional kinematics. The purposes of this study were: 1) to develop a preliminary database of upper extremity movements for two common gestures used in gestural facilitation of naming (GES) training, slicing and hammering, in participants who experienced a left-hemisphere stroke and compare them to age-matched healthy controls, and 2) to perform a case study consisting of a single …

Numerical Study Of The Performance Of A Model Scramjet Engine, Ayad Alhumadi

Mechanical & Aerospace Engineering Theses & Dissertations

A computational parametric investigation was conducted to study the effect of variations to several geometric parameters on the performance of a two-dimensional model scramjet engine (square cross section area for 3-D model). Geometric parameters included backstep location, height, and angle and fuel injector angle, diameter, and location. Two- and three-dimensional geometries have been studied, using a finite-volume computational fluid dynamics (CFD) code (FLUENT) with structured grids with sizes between 50,000 and 90,000 cells for the two-dimensional geometry and with structured hexahedral grid sizes between 650,000 and 949,725 cells for the three-dimensional geometry. Otherwise, identical values of program inputs were utilized …

Dynamic Scheduling For Unplanned Maintenance Work, Tejaswi Karempudi

Mechanical & Aerospace Engineering Theses & Dissertations

Ships are maintained at regular intervals in a scheduled manner. But there may be unexpected problems which necessitate immediate or as-soon-as-possible attention. These kinds of problem are handled through some type of Unplanned Maintenance Scheduling (UMS).

In a recent paper, Bao, Mittal and Dean I presented a method for planning and scheduling maintenance jobs using lean maintenance principles. In this method, the priority levels of the jobs are initially identified through a Maintenance Priority Evaluation Matrix (MPEM), then conflicts between the jobs because of personnel, tooling and spatial uses are taken into account concurrently to force a re-prioritization of the …

A Complete Autonomous Vehicle Solution: An Asv Case Study, Justin Michael Selfridge

Mechanical & Aerospace Engineering Theses & Dissertations

The field of robotics has grown at an astonishing rate over the past two decades, and the interest in autonomous vehicles has grown even faster. Autonomous vehicles offer the unique promise of removing drivers from dangerous environments, and increasing the efficiency of our highways. However, the development of these systems is no trivial task. For an autonomous vehicle to effectively navigate and interact with the world, the vehicle must ( 1) determine where it is located and create an accurate assessment of its surroundings, (2) develop a feasible navigational path based on the current surroundings and the vehicle's destination, and …

Model Verification For Multi-Body Dynamics And Six Degree Of Freedom Machine Impact Testing, Scott James Tedesco

Mechanical & Aerospace Engineering Theses & Dissertations

Using MSC's ADAMS software, a multi-body dynamic model was created to represent a Six Degree of Freedom (Six DOF) Machine, located at the Old Dominion University Dynamic Environment Simulation Laboratory (DES Lab). This rigid body model was verified for single axis impact using experimental test data from the Six DOF Machine. Due to the large number of unknowns in the physical Six DOF Machine, a parameter sensitivity study was conducted to analyze critical parameters. This study provided data regarding machine performance, improved general understanding of the physical and mechanical operation of the Six DOF Machine, and guidance for parameter modeling …

Molecular Dynamics Studies On Nanoscale Gas Transport, Murat Barisik

Mechanical & Aerospace Engineering Theses & Dissertations

Three-dimensional molecular dynamics (MD) simulations of nanoscale gas flows are studied to reveal surface effects. A smart wall model that drastically reduces the memory requirements of MD simulations for gas flows is introduced. The smart wall molecular dynamics (SWMD) represents three-dimensional FCC walls using only 74 wall Molecules. This structure is kept in the memory and utilized for each gas molecule surface collision. Using SWMD, fluid behavior within nano-scale confinements is studied for argon in dilute gas, dense gas, and liquid states. Equilibrium MD method is employed to resolve the density and stress variations within the static fluid. Normal stress …

A Unified Enterprise-Wide Cost Modeling Framework For Engineering Applications Based On Systems Engineering Principles, Yousuf S. Mohammed

Mechanical & Aerospace Engineering Theses & Dissertations

In the present research the problem of enterprise-wide cost modeling is approached from a systems engineering standpoint. What this does is to use each stage of product life cycle to obtain useful information that helps in estimating the cost of the system. Once a generic framework is developed for estimating the core cost, layers of other factors that affect the cost are applied to the core cost, such as risk and uncertainty, maintainability, supply-chain and socioeconomic conditions. The cost model is expanded to accommodate a product domain ranging from a simple object to a system in the following hierarchy: System, …

Dynamics And Control Of Satellite Relative Motion In Proximity Operations, Mohamed Elsayed Aly Abd Elaziz Okasha

Mechanical & Aerospace Engineering Theses & Dissertations

In this dissertation, the development of relative navigation, guidance, and control algorithms of an autonomous space rendezvous and docking system are presented. These algorithms are based on innovative formulations of the relative motion equations that are completely explicit in time. The navigation system uses an extended Kalman filter based on these formulations to estimate the relative position and velocity of the chaser vehicle with respect to the target vehicle and the chaser attitude and gyro biases. This filter uses the range and angle measurements of the target relative to the chaser from a simulated LIDAR system, along with the star …

Electrokinetic Transport Phenomena In Nanofluidic Devices, Mingkan Zhang

Mechanical & Aerospace Engineering Theses & Dissertations

Nanofluidic devices have wide potential applications in biology, chemistry and medicine, and have been proven to be very valuable in sensing biological particles (e.g., DNA and proteins) due to their efficiency, sensitivity and portability. Electrokinetic control of ion, fluid, and particle transport by using only electric field is the most popular method employed in nanofluidic devices. A comprehensive understanding of the electrokinetic ion, fluid, and particle transport in nanofluidics is essential for developing nanofluidic devices for the detection of single molecules, such as the next generation nanopore-based DNA sequencing technology. This research explored numerical simulation of electrokinetic ion and fluid …

Design And Implementation Of A Z-Axis Mems Gyroscope With A Symmetric Multiple-Mass Mechanical Structure, Yujie Zhang

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis presents a z-axis MEMS gyroscope with a symmetric mechanical structure. The multiple-mass design prioritizes the sense-mode Quality Factor (Q) and thus improves its scale factor. The proposed mechanically coupled, dynamically balanced anti-phase sense-mode design minimizes energy dissipation through the substrate in order to maximize the Q. Numerical simulation is implemented in a finite element analysis software, COMSOL, to identify the two operation modes of the gyroscope: drive-mode and sense-mode. The multiple-mass gyroscope design is further fabricated using a one-mask process. Experimental characterization of frequency response in both drive-mode and sense-mode of the device are conducted, proving the design …

Large-Eddy Simulation Of Axially-Rotating, Turbulent Pipe And Particle-Laden Swirling Jet Flows, Nicolas D. Castro

Mechanical & Aerospace Engineering Theses & Dissertations

The flows of fully-developed turbulent rotating pipe and particle-laden swirling jet emitted from the pipe into open quiescent atmosphere are investigated numerically using Large-Eddy Simulation (LES). Simulations are performed at various rotation rates and Reynolds numbers, based on bulk velocity and pipe diameter, of 5.3x103, 12x103, and 24x103, respectively. Time-averaged LES results are compared with experimental and simulation data from previous studies. Pipe flow results confirm observations in previous studies, such as the deformation of the turbulent mean axial velocity profile towards the laminar Poiseuille-profile, with increased rotation. The Reynolds stress anisotropy tensor shows a redistribution due to pipe rotation. …

Transient Finite Element Analysis Of A Base Excited Frame On A Six Dof Motion Simulator To Simulate Wave Slamming, Matthew Douglas Davis

Mechanical & Aerospace Engineering Theses & Dissertations

High speed performance crafts are subjected to repeated impact loads in open seas. In this study, an attempt is made to investigate the dynamic response of onboard equipment under an impact environment generated by a 6 degree-of-freedom (DOF) motion simulator. An aluminum frame is used to represent onboard equipment, which is mounted on the 6 DOF motion simulator at various orientations and with varying amounts of additional weight. A series of 15 single-axis drop tests are conducted with the DOF motion simulator to study the effects of these impact loads on the onboard equipment. The test data is analyzed to …

Study Of The Role Of Pressure Relaxation In Inviscid, Incompressible Flows, Jonathan Strzelec

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis has investigated the role of pressure relaxation in inviscid, incompressible flows. A modified form of the classical Bernoulli equation was developed from a vector form of the Navier-Stokes equation which includes pressure relaxation and bulk viscosity. This modified Bernoulli equation was utilized to compare two-dimensional potential flow pressure distributions over a sphere, cylinder, backward and forward facing steps. Finally, the modified Bernoulli equation was utilized to compare the theoretical bounding free streamline to an experimentally observed free streamline over a knife edge. Results of these comparisons show that the classical form of the Bernoulli equation can over-predict the …

Marine Pollution And Energy Calculation Study Of Impacts Of Speed Reduction And Hull Roughness, Aditi Patil

Mechanical & Aerospace Engineering Theses & Dissertations

About 3.3% of global air ermss1ons m 2007 were due to international shipping operations. If no policies are enacted, the Green House Gas (GHG) emissions would increase by a factor of 2-3 by 2050.

In order to reduce Global Warming, international institutions such as the International Marine Organization and European Maritime Authorities are implementing policies for reduction of NO_x and SO_x by 2020. Regulations for these gases are indicated in MARPOL Annex VI.

There are four fundamental ways of reducing emissions:

• Improving energy efficiency by modifying ship design or operation strategy

• Using renewable energy sources for …

The Transfer Of Laser-Machined Micro-Structured Patterns From Silicon To Polymethyl Methacrylate, Warren E. Withrow

Mechanical & Aerospace Engineering Theses & Dissertations

This research project's purpose was transferring a micro-scaled pattern from a silicon wafer to a polymethyl methacrylate (PMMA), or acrylic, substrate through light absorption generated heat. The secondary objective was to determine if the pattern on the silicon wafer could then be transferred to silica (i.e. a microscope glass slide) through light absorption generated heat. Once this pattern-transfer technique is developed for the micro scale, it could be instituted on the nano scale. The experiment was designed to find an alternate method to that currently being used to mass-produce compact discs (CDs). The most popular method employs a stamping process …

Interface Circuit For A Multiple-Beam Tuning-Fork Gyroscope With High Quality Factors, Ren Wang

Mechanical & Aerospace Engineering Theses & Dissertations

This research work presents the design, theoretical analysis, fabrication, interface electronics, and experimental results of a Silicon-On-Insulator (SOI) based Multiple-Beam Tuning-Fork Gyroscope (MB-TFG). Based on a numerical model of Thermo-Elastic Damping (TED), a Multiple-Beam Tuning-Fork Structure (MB-TFS) is designed with high Quality factors (Qs) in its two operation modes. A comprehensive theoretical analysis of the MB-TFG design is conducted to relate the design parameters to its operation parameters and further performance parameters. In conjunction with a mask that defines the device through trenches to alleviate severe fabrication effect on anchor loss, a simple one-mask fabrication process is employed to implement …

Long Term Surface Power Generator Design For Mars: Autonomously Deployable Photovoltaic Solar Arrays Along With Regenerative Fuel Cell Modules, Omer Demirok

Mechanical & Aerospace Engineering Theses & Dissertations

This thesis studies the feasibility of incorporating a large autonomously deployed photovoltaic solar array power system as the primary power source for a large fixed Mars base. A mission duration of 10 Earth years has been assumed and the nominal power demands have been specified as a minimum of 40 kW, during daytime operation and a continuous 10 kW. demand for nighttime operation.

The overall system design developed in this thesis has an estimated total mass of 7,400 kg, when utilizing hydrogenated amorphous silicon thin film solar arrays and an estimated total mass of 5,100 kg when utilizing polycrystalline copper-indium-diselenide …

Multidisciplinary Design Optimization Of Transonic Airfoil Sections Using Multiobjective Optimization And Computational Intelligence Tools, Amit A. Kulkarni

Mechanical & Aerospace Engineering Theses & Dissertations

The design of transonic airfoils for civil aviation applications has been a major engineering challenge in the last fifty years. This design problem arises due to the need to limit shock wave drag at a given transonic speed. In recent years, the requirement to reduce the levels of aircraft noise has started to affect the airfoil design process. The multidisciplinary aerodynamic shape optimization problem is treated in this thesis using a multi-objective approach. The objectives correspond to the design of transonic airfoil sections with low drag during cruise and low trailing edge noise levels during the approach condition. The optimization …

A Pilot Model For Investigating Biodynamic Coupling Due To Aeroservoelastic Accelerations, Brandon Cowen

Mechanical & Aerospace Engineering Theses & Dissertations

Supersonic Transport Aircraft tend to have slender fuselages with respect to their subsonic counterparts. This design feature leads to increased aeroservoelastic bending at low resonant frequencies closer to the frequencies of pilot commands and the corresponding rigid body accelerations. Aeroelastic accelerations of certain frequencies and phase lags at the pilot station have been seen to involuntarily pass through the pilot's body to the control inceptor. When the pilot commands rigid body accelerations in phase with the structural response, the structural accelerations grow. Thus biodynamic coupling represents the coupling between the feedthrough of pilot station acceleration through the pilot's body, with …

Direct Current Electrokinetic Particle Transport In Micro/Nano-Fluidics, Ye Ai

Mechanical & Aerospace Engineering Theses & Dissertations

Electrokinetics has been widely used to propel and manipulate particles in micro/nano-fluidics. The first part of this dissertation focuses on numerical and experimental studies of direct current (DC) electrokinetic particle transport in microfluidics, with emphasis on dielectrophoretic (DEP) effect. Especially, the electrokinetic transports of spherical particles in a converging-diverging microchannel and an L-shaped microchannel, and cylindrical algal cells in a straight microchannel have been numerically and experimentally studied. The numerical predictions are in quantitative agreement with our own and other researchers' experimental results. It has been demonstrated that the DC DEP effect, neglected in existing numerical models, plays an important …

Manipulating Particles For Micro- And Nano-Fluidics Via Floating Electrodes And Diffusiophoresis, Sinan Eren Yalcin

Mechanical & Aerospace Engineering Theses & Dissertations

The ability to accurately control micro- and nano-particles in a liquid is fundamentally useful for many applications in biology, medicine, pharmacology, tissue engineering, and microelectronics. Therefore, first particle manipulations are experimentally studied using electrodes attached to the bottom of a straight microchannel under an imposed DC or AC electric field. In contrast to a dielectric microchannel possessing a nearly-uniform surface charge, a floating electrode is polarized under the imposed electric field.

The purpose is to create a non-uniform distribution of the induced surface charge, with a zero-net-surface charge along the floating electrode's surface. Such a field, in turn, generates an …

Balloon Borne Mars Research Platforms, Sean Michael Hancock

Mechanical & Aerospace Engineering Theses & Dissertations

Aerial platforms can fill a measurement gap between orbiters and rovers, providing planetary scale high resolution in situ measurements, access to scientifically interesting terrain that is either inaccessible or hazardous to rovers, and serve as a planet-wide delivery platforms to deploy surface probes and rovers to areas inaccessible given existing entry, descent, and landing systems. A permanent robotic outpost on the Martian surface can utilize locally-derived hydrogen as a lifting gas for balloon systems deployed from Mars. That approach can simplify the inflation and launch of aerial vehicles while allowing for a long duration deployment campaign that is not constrained …