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Articles 61 - 90 of 95
Full-Text Articles in Mechanical Engineering
Primary Resonance Behavior Of Expanded Polymer Cushion Material Under Low-Intensity Harmonic Excitations, Gregory Batt
Primary Resonance Behavior Of Expanded Polymer Cushion Material Under Low-Intensity Harmonic Excitations, Gregory Batt
All Dissertations
The demand to lower costs and reduce the amount of packaging materials utilized in a packaged-product system has placed increased importance on the development of tools to model the behavior of packaging systems. In this dissertation, the free and forced vibration response of a nonlinear, distributed-parameter model of a viscoelastic rod with an applied tip-mass is used to investigate the response of expanded polymer cushion materials to low-intensity harmonic excitations. The rod and tip-mass represent an idealized packaged product system. A nonlinear model is developed from constitutive relations. A classical Maxwell-Weichert model, represented via a Prony series, is used to …
Model Based Control Of Machining Processes: Exploration Of Bayesian Statistical Methods For Identification And Control, Parikshit Mehta
Model Based Control Of Machining Processes: Exploration Of Bayesian Statistical Methods For Identification And Control, Parikshit Mehta
All Dissertations
Machining process modeling & simulation as well as in-process monitoring and control have been identified as key technological factors to power efficient manufacturing facilities of tomorrow. The effective utilization of process models and in-process control are aimed towards improving profitability of the manufacturing process. To that end, the objective of this research work is to improve machining performance by implementing in-process control using model based control strategies, while considering stochastic models of machining process. Towards satisfying that objective, three research questions are asked.
1) What are metrics of measuring machining performance and which machining process models are important to consider …
Jet Instability And Droplet Formation For Bio-Printing Applications, Leigh Herran
Jet Instability And Droplet Formation For Bio-Printing Applications, Leigh Herran
All Dissertations
The research conducted in this dissertation was done to obtain a fundamental understanding of the formation of droplets in a drop-on-demand (DOD) inkjetting setup when the ink contains a polymer additive. The objective is to precisely control and even predict the forming dynamics and final droplet characteristics (velocity, size and satellite elimination). A polymeric fluid called sodium alginate has been gaining attention due to its highly bio-compatible nature. Solutions of sodium alginate were used as the ink material and in some cases compared with an equivalent Newtonian fluid (same zero-shear viscosity). The droplets were inspected in one of two ways: …
Stability Control Of Triple Trailer Vehicles, Michael O'Neal Arant
Stability Control Of Triple Trailer Vehicles, Michael O'Neal Arant
All Dissertations
While vehicle stability control is a well-established technology in the passenger car realm, it is still an area of active research for commercial vehicles as indicated by the recent notice of proposed rulemaking on commercial vehicle stability by the National Highway Traffic Safety Administration (NHTSA, 2012). The reasons that commercial vehicle electronic stability control (ESC) development has lagged passenger vehicle ESC include the fact that the industry is generally slow to adopt new technologies and that commercial vehicles are far more complex requiring adaptation of existing technology. From the controller theory perspective, current commercial vehicle stability systems are generally passenger …
Prediction Of Discrete Element Parameters For Modeling The Strength Of Sandy Soils In Wheel/Soil Traction Applications, Timothy Reeves
Prediction Of Discrete Element Parameters For Modeling The Strength Of Sandy Soils In Wheel/Soil Traction Applications, Timothy Reeves
All Dissertations
The problem of wheel performance on deformable soil has been studied for many years, but prior to the rise of computational mechanics, such investigations have been limited to development of analytical and empirical models, as well as experimental research. Such models have merit but are necessarily highly idealized and are limited in their applications. Today, many computational models have been implemented for a wide variety of wheel/soil applications.
For the specific case of sandy (i.e. non-cohesive) soils, in terms of the soil's physics the Discrete Element Method (DEM) provides arguably the most realistic model. In DEM, each element represents a …
Understanding The Role Of Nonlinearities In The Transduction Of Vibratory Energy Harvesters, Ravindra Masana
Understanding The Role Of Nonlinearities In The Transduction Of Vibratory Energy Harvesters, Ravindra Masana
All Dissertations
The last two decades have witnessed several advances in micro-fabrication technologies and electronics, leading to the development of small, low-power devices for wireless sensing, data transmission, actuation, and medical implants. Unfortunately, the actual implementation of such devices in their respective environment has been hindered by the lack of scalable energy sources that are necessary to power and maintain them. Batteries, which remain the most commonly used power source, have not kept pace with the demands of these devices, especially in terms of energy density. In light of this challenge, the concept of vibratory energy harvesting has flourished in recent years …
Network Target Coordination For Design Optimization Of Decomposed Systems, Wenshan Wang
Network Target Coordination For Design Optimization Of Decomposed Systems, Wenshan Wang
All Dissertations
A complex engineered system is often decomposed into a number of different subsystems that interact on one another and together produce results not obtainable by the subsystems alone. Effective coordination of the interdependencies shared among these subsystems is critical to fulfill the stakeholder expectations and technical requirements of the original system. The past research has shown that various coordination methods obtain different solution accuracies and exhibit different computational efficiencies when solving a decomposed system. Addressing these coordination decisions may lead to improved complex system design. This dissertation studies coordination methods through two types of decomposition structures, hierarchical, and nonhierarchical.
For …
On Simulation And Modeling Of Turbulent Non-Premixed Reacting Shear Flames At Low And High Pressure, Justin Foster
On Simulation And Modeling Of Turbulent Non-Premixed Reacting Shear Flames At Low And High Pressure, Justin Foster
All Dissertations
A database of simulations of fundamental turbulent H2/O2 and H2/Air shear layer flames has been developed using the direct numerical simulation technique in which all length and time scales of a flow are fully resolved without resort to turbulence modeling. The formulation includes the fully-compressible form of the governing equations, a pressure dependent detailed chemical kinetics scheme (9 species, 19 steps), a cubic real gas equation of state, realistic property models, and generalized heat and mass diffusion models. Simulations were conducted for a temporally developing shear layer geometry and cover a wide range of initial pressures (1 atm < P < 125 atm) and flame Reynolds numbers (850 < Re < 4500). These supercomputing simulations are the largest yet performed for high pressure conditions to the author's knowledge. Computational requirements for the largest simulations included mesh sizes of ~3/4 billion grid points and ~2.2 million CPU-hrs conducted on nearly 4,000 CPU cores on Clemson's Palmetto cluster.
The database …
Compressive Strength Of Continuous Fiber Unidirectional Composites, Ronald Thompson
Compressive Strength Of Continuous Fiber Unidirectional Composites, Ronald Thompson
All Dissertations
Dow and Rosen's work in 1965 formed an intellectual framework for compressive strength of unidirectional composites. Compressive strength was explained in terms of micro-buckling, in which filaments are beams on an elastic foundation. They made simplifying assumptions, with a two dimensional idealization and linearized material properties. This study builds on their model, recognizing that the shear mode of instability drives unidirectional compressive strength. As a necessary corollary, the predictive methods developed in this study emphasize correct representation of composite shear stiffness. Non-linear effects related to matrix material properties, fiber misalignment, three dimensional representation, and thermal prestrains are taken into account. …
Computational Representation And Reasoning Support For Requirements Change Management In Complex System Design, Beshoy Morkos
Computational Representation And Reasoning Support For Requirements Change Management In Complex System Design, Beshoy Morkos
All Dissertations
Requirements play a critical role within any design process and the activity of identifying and maintaining a system's requirements is essential to. However, design is a complex and iterative process, where requirements are continuously evolving and are volatile. This change, if not managed, may result in undesired uncertainty within the design process leading to monetary losses and time delays, as the changing of requirements has been recognized as a major cause of project failure. In order to mitigate issues that arise due to requirement change propagation, this research presents a computational reasoning tool to help designers and engineers predict change …
Design Of Meta-Materials Outside The Homogenization Limit Using Multiscale Analysis And Topology Optimization, Christopher Czech
Design Of Meta-Materials Outside The Homogenization Limit Using Multiscale Analysis And Topology Optimization, Christopher Czech
All Dissertations
The field of meta-materials engineering has largely expanded mechanical design possibilities over the last two decades; some notable design advances include the systematic engineering of negative Poisson's ratio materials and functionally graded materials, materials designed for optimal electronic and thermo-mechanical performances, and the design of materials under uncertainty. With these innovations, the systematic engineering of materials for design-specific uses is becoming more common in industrial and military uses. The motivation for this body of research is the design of the shear beam for a non-pneumatic wheel. Previously, a design optimization of a finite element model of the non-pneumatic wheel was …
Clustering And Classification Of Multivariate Stochastic Time Series In The Time And Frequency Domains, Ryan Schkoda
Clustering And Classification Of Multivariate Stochastic Time Series In The Time And Frequency Domains, Ryan Schkoda
All Dissertations
The dissertation primarily investigates the characterization and discrimination of stochastic time series with an application to pattern recognition and fault detection. These techniques supplement traditional methodologies that make overly restrictive assumptions about the nature of a signal by accommodating stochastic behavior. The assumption that the signal under investigation is either deterministic or a deterministic signal polluted with white noise excludes an entire class of signals -- stochastic time series. The research is concerned with this class of signals almost exclusively. The investigation considers signals in both the time and the frequency domains and makes use of both model-based and model-free …
Applying Chaotic Advection To Rheology: An In Situ Structuring Rheometer, Ramaswami Subrahmanian
Applying Chaotic Advection To Rheology: An In Situ Structuring Rheometer, Ramaswami Subrahmanian
All Dissertations
A prototype In Situ Structuring Rheometer (ISSR) was designed and implemented to study changes in shear viscosity of polymer blends and composites while processing them in such a way as to control the evolution of microstructure. The ISSR is based on a regime of fluid mechanics known as chaotic advection, in which simple time-periodic flow fields can cause fluid particles to move chaotically. Chaotic advection is also the basis of Smart Blending, a technology employed to process polymer blends having a variety of morphologies at a fixed composition, and polymer composites in which the additives have been arranged into layered …
Extending Origami Technique To Fold Forming Of Sheet Metal Products, Ala Qattawi
Extending Origami Technique To Fold Forming Of Sheet Metal Products, Ala Qattawi
All Dissertations
This dissertation presents a scientific based approach for the analysis of folded sheet metal products. Such analysis initializes the examination in terms of topological exploration using set of graph modeling and traversal algorithms. The geometrical validity and optimization are followed by utilizing boundary representation and overlapping detection during a geometrical analysis stage, in this phase the optimization metrics are established to evaluate the unfolded sheet metal design in terms of its manufacturability and cost parameters, such as nesting efficiency, total welding cost, bend lines orientation, and maximum part extent, which aides in handling purposes. The proposed approach evaluates the design …
A Formal Representation Of Mechanical Functions To Support Physics-Based Computational Reasoning In Early Mechanical Design, Chiradeep Sen
A Formal Representation Of Mechanical Functions To Support Physics-Based Computational Reasoning In Early Mechanical Design, Chiradeep Sen
All Dissertations
The lack of computational support to the conceptual phase of mechanical engineering design is well recognized. Function-based modeling and thinking is widely recommended in design texts as useful means for describing design concepts and using them in tasks such as solution search, problem decomposition, and design archival. Graph-based function structure models that describe a product as a network of transformative actions of material, energy, and information, are discussed as a potential tool for this purpose, but in the current state of the art, function structures are not formalized as a computational representation. Consequently, no computer tool exists with which a …
An Investigation Of The Application Of Phase Change Materials In Practical Thermal Management Systems, David Ewing
An Investigation Of The Application Of Phase Change Materials In Practical Thermal Management Systems, David Ewing
All Dissertations
This work investigates the application of alternative cooling techniques to thermal management. In the first section, this work presents models and extensive simulation studies on an alternative cooling strategy based upon phase change materials (PCMs) for the thermal management system of a LED headlight assembly. These studies have shown that properly chosen PCMs, when suspended in metal foam matrices, increased the thermal conductivity of the PCM. The increased thermal conductivity can enhance the cooling characteristics of a practical thermal management system for a LED headlight system. To further enhance the advantages of using PCMs, nanoparticle enhanced fluids (nanofluids) are desirable …
Optimization-Based Power Management Of Hybrid Power Systems With Applications In Advanced Hybrid Electric Vehicles And Wind Farms With Battery Storage, Hoseinali Borhan
Optimization-Based Power Management Of Hybrid Power Systems With Applications In Advanced Hybrid Electric Vehicles And Wind Farms With Battery Storage, Hoseinali Borhan
All Dissertations
Modern hybrid electric vehicles and many stationary renewable power generation systems combine multiple power generating and energy storage devices to achieve an overall system-level efficiency and flexibility which is higher than their individual components. The power or energy management control, ``brain' of these ``hybrid' systems, determines adaptively and based on the power demand the power split between multiple subsystems and plays a critical role in overall system-level efficiency. This dissertation proposes that a receding horizon optimal control (aka Model Predictive Control) approach can be a natural and systematic framework for formulating this type of power management controls. More importantly the …
Fabrication Of Grooved Hollow Fiber Membrane For Nerve Regeneration: Process Modeling And Performance Evaluation, Jun Yin
All Dissertations
Nerve injury is a general but intractable disease in traumatic injuries, leading to a significant reduction of functions in the nervous system. Extensive efforts are made on nerve injury rehabilitation. Since the appropriate connections between neurons and their targets are necessary, guiding axonal outgrowth is an essential step for neuron outgrowth in nervous system development, functioning, and regeneration. Besides the direct surgical nerve connection, an artificial means of guiding nerve regeneration called nerve conduits is widely applied in nerve injury rehabilitation. The main function of nerve conduits is to bridge the nerve gap, to help regenerating axons across damaged regions …
Effect Of Relative Humidity And Temperature Control On In-Cabin Thermal Comfort State, Ali Alahmer
Effect Of Relative Humidity And Temperature Control On In-Cabin Thermal Comfort State, Ali Alahmer
All Dissertations
This dissertation discusses the effect of manipulating the relative humidity RH levels inside vehicular cabins on the thermal comfort and human occupants' thermal sensation. Three different techniques are used to investigate this effect. Firstly, thermodynamic and psychometric analyses are used to incorporate the effect of changing RH along with the dry bulb temperature on the human comfort window. Specifically, the study computes the effect of changing the relative humidity on the amount of heat rejected from the passenger compartment and the effect on occupants comfort zone. A practical system implementation is also discussed in terms of an evaporative cooler design. …
Evaluating The Use Of Functional Representations For Ideation In Conceptual Design, Benjamin Caldwell
Evaluating The Use Of Functional Representations For Ideation In Conceptual Design, Benjamin Caldwell
All Dissertations
Functional representations are often used in the conceptual stages of design because they encourage the designer to focus on the intended use and purpose of a system rather than the physical solution. Function models have been proposed by many researchers as a tool to expand the solution search space and guide concept generation, and many design tools have been created to support function-based design. These tools require designers to create function models of new or existing artifacts, but there is limited published research describing what types of functions should be included in a model or the appropriate level of abstraction …
Development Of A Design Method To Reduce Change Propagation Effects, Prabhu Shankar
Development Of A Design Method To Reduce Change Propagation Effects, Prabhu Shankar
All Dissertations
ABSTRACT
This dissertation presents a design method to reduce engineering changes caused due to change propagation effect. The method helps designers to systematically plan a verification, validation, and test (VV&T) plan. The rationale behind such a method is founded on a well-accepted principle that a robust validation plan can reduce design changes. However, such method has not yet been developed in mechanical engineering domain, so a method from software engineering has been adopted and extended to address the limitations in the existing design evaluation tools.
Tools extensively used in industry, such as FMEA, and in academia have been reviewed to …
Computational-Analysis Assisted Introduction Of Friction Stir Welding Into Development Of Light-Weight High-Survivability Military Vehicles, Guruprasad Arakere
Computational-Analysis Assisted Introduction Of Friction Stir Welding Into Development Of Light-Weight High-Survivability Military Vehicles, Guruprasad Arakere
All Dissertations
High strength aluminum alloys with superior blast/ballistic resistance against armor piercing (AP) threats and with high vehicle light-weighing potential are being increasingly used as military-vehicle armor. Due to the complex structure of these vehicles, they are commonly constructed through joining (mainly welding) of the individual components. Unfortunately, these alloys are not very amenable to conventional fusion based welding technologies (e.g. Gas Metal Arc Welding (GMAW)) and in-order to obtain high-quality welds, solid-state joining technologies such as Friction Stir Welding (FSW) have to be employed. However, since FSW is a relatively new and fairly complex joining technology, its introduction into advanced …
Investigation Of Two-Phase Behavior In Capillary Evaporators With Liquid Core Visualization, Brian D'Entremont
Investigation Of Two-Phase Behavior In Capillary Evaporators With Liquid Core Visualization, Brian D'Entremont
All Dissertations
The Capillary Pumped Loop (CPL) and Loop Heat Pipe (LHP) are thermal management devices which are high performance derivatives of the conventional heat pipe. Both consist of a discrete evaporator containing a porous solid wick which is coupled via smoothed walled tubing to a condenser. In a CPL, fluid inventory is managed by a reservoir attached to the liquid line which is controlled in temperature. In an LHP, fluid inventory is managed passively by a compensation chamber which is integral to the evaporator.
In this study, a borescope was inserted into the liquid core and compensation chamber of LHP evaporators …
Multi-Length Scale Modeling Of The High-Pressure, Large-Strain, High-Strain-Rate Response Of Soda-Lime Glass, William Bell
Multi-Length Scale Modeling Of The High-Pressure, Large-Strain, High-Strain-Rate Response Of Soda-Lime Glass, William Bell
All Dissertations
Development of new transparent armor systems is essential for the protection of the current and future US armed forces, especially in light of the recent military operations The Operation Iraqi Freedom in Iraq and The Operation Enduring Freedom in Afghanistan. These conflicts have introduced a new military theater without a well-defined battle front and new types of threats (e.g. improvised explosive devices, IEDs). Development and modeling of new transparent armor systems for use in numerous applications from vehicle windows to face shields is a current area of thrust aimed at addressing the shortcomings of existing systems in order to better …
Electrokinetic Transport And Manipulation Of Particles In Curved Microchannels, Junjie Zhu
Electrokinetic Transport And Manipulation Of Particles In Curved Microchannels, Junjie Zhu
All Dissertations
The investigation of electrokinetic particle transport in confined microchannels has practical significances in a variety of applications ranging from traditional gel electrophoresis to electrokinetic microfluidics-based lab-on-a-chip devices. To date, however, studies on particle electrokinetics have been limited to primarily theoretical or numerical analyses in straight microchannels of simple geometries. Very little work has been done on electrokinetic particle motions in real microchannels which usually consist of one or multiple turns. This thesis is dedicated to the fundamental and applied studies of electrokinetic transport and manipulation of particles in various curved microchannels using a combined experimental, theoretical, and numerical method.
First, …
An Investigation Of The Effects Of Surfactant Monolayers On Natural Convection Heat Transfer And Evaporative Mass Transfer, Steven Bower
An Investigation Of The Effects Of Surfactant Monolayers On Natural Convection Heat Transfer And Evaporative Mass Transfer, Steven Bower
All Dissertations
Laboratory experiments are presented that reveal the effects of surfactant monolayers on natural convection heat transfer and evaporation from bodies of water; more specifically, the situation is studied where the bulk temperature of the water is greater than the temperature of the air so that evaporative convection occurs. Four sets of experiments were performed in a laboratory environment on insulated tanks of different widths and depths for the following surface conditions: 1) clean surface, 2) oleyl alcohol covered surface, 3) stearic acid covered surface, and 4) stearyl alcohol covered surface. An infrared (IR) camera was used to verify the existence …
Mixture Fraction Imaging Based On Photodissociation Spectroscopy And Two Photon Laser Induced Fluorescence, Yan Zhao
All Dissertations
The study of turbulent combustion calls for new diagnostics that can measure multidimensional mixture fraction under a wide range of flame conditions. A laser diagnostic technique based on photodissociation spectroscopy (PDS) is proposed to address this need. This thesis describes the concept of the PDS-based diagnostic, reports its experimental demonstration in a non-premixed jet flame, and assesses its performance and applicable range. The two-photon laser induced fluorescence (TPLIF) technique used in conjugate with the PDS is analyzed numerically in line and planar imaging configuration.
The new mixture fraction imaging technique is centered around the creative use of photodissociation (PD) for …
A Methodology For The Analysis Of In-Vehicle Operating Data And Design Of Intelligent Vehicle Systems For Improved Automotive Safety, Matthew Jensen
A Methodology For The Analysis Of In-Vehicle Operating Data And Design Of Intelligent Vehicle Systems For Improved Automotive Safety, Matthew Jensen
All Dissertations
Every year global motorization increases as more motor vehicles are manufactured, and the total number of vehicle miles traveled rises. These increased travel opportunities result in higher numbers of injuries, fatalities, and monetary losses associated with traffic-related crashes. In the last decade, hundreds of thousands of people were killed by vehicle collisions in the United States. The World Health Organization has labeled traffic crashes as the ninth leading cause of global disease; by the year 2020, traffic crashes are expected to rise to number three. An opportunity exists to improve global human safety through research and innovation in driver training …
Implementation Of Delayed-Feedback Controllers On Continuous Systems And Analysis Of Their Response Under Primary Resonance Excitations, Yousef Qaroush
Implementation Of Delayed-Feedback Controllers On Continuous Systems And Analysis Of Their Response Under Primary Resonance Excitations, Yousef Qaroush
All Dissertations
During the last three decades, a considerable amount of research has been directed toward understanding the influence of time delays on the stability and stabilization
of dynamical systems. From a control perspective, these delays can either have a compounding and destabilizing effect, or can actually improve controllers'
performance. In the latter case, additional time delay is carefully and deliberately introduced into the feedback loop so as to augment inherent system delays and
produce larger damping for smaller control efforts. While delayed-feedback algorithms have been successfully implemented on discrete dynamical systems with
limited degrees of freedom, a critical issue appears in …
High Resolution Vision-Based Servomechanism Using A Dynamic Target With Application To Cnc Machines, Carlos Montes-Solano
High Resolution Vision-Based Servomechanism Using A Dynamic Target With Application To Cnc Machines, Carlos Montes-Solano
All Dissertations
This dissertation introduces a novel three dimensional vision-based servomechanism with application to real time position control for manufacturing equipment, such as Computer Numerical Control (CNC) machine tools. The proposed system directly observes the multi-dimensional position of a point on the moving tool relative to a fixed ground, thus bypassing the inaccurate kinematic model normally used to convert axis sensor-readings into an estimate of the tool position.
A charge-coupled device (CCD camera) is used as the position transducer, which directly measures the current position error of the tool referenced to an absolute coordinate system. Due to the direct-sensing nature of the …