Mechanical Engineering Commons^™

Impinging Jet Spray Formation Using Non-Newtonian Liquids, Neil S. Rodrigues

Open Access Theses

Over the past two decades there has been a heightened interest in implementing gelled propellants for rocket propulsion, especially for hypergolic bi-propellants such as monomethylhydrazine (MMH) and nitrogen tetroxide oxidizer (NTO). Due to the very high level of toxicity of hypergolic liquid rocket propellants, increasing safety is an important area of need for continued space exploration and defense operations. Gelled propellants provide an attractive solution to meeting the requirements for safety, while also potentially improving performance. ^ A gelling agent can be added to liquid propellants exhibiting Newtonian behavior to transform the liquid into a non-Newtonian fluid with some solid-like …

Design Of A High Performance Actuation System Enabled By Energy Coupling Actuation, Daniel Richard Skelton

Open Access Theses

The main goal of the research was to design, manufacture, and test a new linear actuation system. Research was conducted on several types of actuation methods applied to hydraulic valves. A literature review showed that most existing actuator systems have the actuator and control mass coupled together. There is a need for high speed actuation. The proposed idea is to have the actuation mass always moving while accelerating and decelerating the control mass. The decoupling of these two will allow for the actuation and control mechanism to be independent and only move the control mechanism when needed. Initial modeling, as …

Development, Numerical Demonstration And Experimental Verification Of A Method For Model Updating Of Boundary Conditions, Christian Eduardo Silva Salazar

Open Access Theses

The study of vibrations in beams has been largely addressed by authors and researchers. However, relatively few researchers have considered the case of unknown boundary conditions, as usually it is reasonable to assume the classical cases such as simply supported, clamped or free. Indeed, there are a wide variety of boundary-condition configurations, each one representing a whole different problem with its own modal characteristics. ^ A method for updating experimental beam models to specifically address the issue of unknown boundary conditions is proposed. This methodology takes advantage of vector comparison techniques such as the modal assurance criterion and the dot …

The Prediction Of Airborne And Structure-Borne Noise Potential For A Tire, Nicholas Sakamoto

Open Access Theses

Tire/pavement interaction noise is a major component of both exterior pass-by noise and vehicle interior noise. The current testing methods for ranking tires from loud to quiet require expensive equipment, multiple tires, and/or long experimental set-up and run times. If a laboratory based off-vehicle test could be used to identify the airborne and structure-borne potential of a tire from its dynamic characteristics, a relative ranking of a large group of tires could be performed at relatively modest expense. This would provide a smaller sample set of tires for follow-up testing and thus save expense for automobile OEMs. The focus of …

Design And Development Of A Novel Test Method To Measure The Slipper / Swashplate Interface Fluid Film In A Positive Displacement Machine, Natalie A. Spencer

Open Access Theses

Although robust models of fluid film behavior between the slipper / swashplate lubricating interface in positive displacement machines have been developed, measuring this same fluid film thickness to a highly accurate degree inside a relatively unaltered axial piston unit has never been accomplished until now. A test method was created to close this gap in available data by measuring fluid film thickness between the slipper and swashplate in a 130cc axial piston pump. Precise knowledge of the gap height between the slipper and swashplate at various shaft angle locations during operation provides critical insight into machine behavior. The design, validation, …

A Numerical Procedure To Design The Optimal Axial Balance In External Gear Machines And Its Potential In Formulating Novel Efficient Design Solutions, Divya Thiagarajan

Open Access Theses

A novel numerical procedure to design the optimal axial balance in external gear machines (EGMs) has been formulated and developed in the present study. Lateral lubricating interfaces exist between the lateral bushes and the rotating gears in pressure compensated designs of EGMs and play a significant role in minimizing power losses arising from fluid shear stress and leakages from the gap. Moreover, lateral bushes in pressure compensated designs of EGMs perform significant functions of sealing the tooth space volumes while they transfer fluid from the inlet to the outlet port. ^ The losses from the lateral gap from these two …

A Web-Based Online Collaboration Platform For Formulating Engineering Design Projects, Sainath Varikuti

Open Access Theses

Effective communication and collaboration among students, faculty and industrial sponsors play a vital role while formulating and solving engineering design projects. With the advent in the web technology, online platforms and systems have been proposed to facilitate interactions and collaboration among different stakeholders in the context of senior design projects. However, there are noticeable gaps in the literature with respect to understanding the effects of online collaboration platforms for formulating engineering design projects. Most of the existing literature is focused on exploring the utility of online platforms on activities after the problem is defined and teams are formed. Also, there …

Optical Direct-Write Nanolithography Based On Self-Assembled Resist, Meghana Akella

Open Access Theses

Holographic display is being developed for next generation mobile phones. However, manufacturing of miniature gratings for the holographic projectors cost a few thousand dollars today, not making the concept practical for commercial purposes. In this thesis, we discuss the feasibility of self-assembled nanoparticles to manufacture holographic gratings cost-effectively and at the nanoscale. Using our approach, the gratings can be manufactured at the scale of 20nm and the cost per chip is expected to cost a few dollars.^ In this thesis, a hydrophobic SAM was used to modify the surface of silicon. Direct-write UV laser lithography was used for photothermal patterning …

Transverse Compression Of High-Performance Ballistic Fibers, Zherui Guo

Open Access Theses

High performance ballistic fibers have been in use for decades, specifically in protective applications against ballistic impact such as bulletproof vest layers and aircraft turbine engine fragmentation barriers. These high performance fibers have extremely high strength-to-weight ratios and high moduli of elasticity in the axial direction, making them extremely suitable for high impact situations. In particular, para-phenyleneterephthalamide (PPTA for short) fibers such as Kevlar^® and ultra-high-molecular-weight polyethylene fibers such as Dyneema^® are amongst the more popular high performance fibers in today's world. While the longitudinal mechanical response of these fibers have been extensively researched, their transverse mechanical response …

Cylinder Block / Valve Plate Interface Performance Investigation Through The Introduction Of Micro-Surface Shaping, Rene Chacon Portillo

Open Access Theses

Swash plate type axial piston machines are widely used positive displacement machines in different fields of industry ranging from aerospace, agriculture, automotive, heavy machinery, etc. Lubricating gaps are the main source of energy dissipation in axial piston machines. This type of machines have three lubricating interfaces: slipper/swash plate interface, piston cylinder and the cylinder block/valve plate interface. The cylinder block/valve plate interface being one of the most critical design elements of the machine. Extensive research has been done at Maha Fluid Power Research Center in Purdue University both to model this interface and to study the effects of micro-surface shaping …

Design, Development And Testing Of A Balance Board With Variable Torsional Stiffness And Time Delay, Denise Renee Cruise

Open Access Theses

The ability to balance and maintain upright posture can decline for a variety of reasons, such as aging and neuromuscular impairment. As the ability to balance declines, the risk of falling increases. Falls are a major cause of injury, and often lead to a dramatic decline in quality of life. Currently, to alleviate balance deficiencies, people participate in balance training, which most commonly refers to standing on an unstable balance board; the most common boards used are either passive wobble boards, or more advanced commercial systems such as the Biodex System SD ® or the Neurocom SMART Balance Master® . …

Laboratory Apparatus For Gas Turbine Combustion Development, Dustin Lee Cruise

Open Access Theses

The next generation of combustor technology will be required to meet the demands of a world more focused on greenhouse gases and global warming. Due to this new focus on emission control, combustors must produce less NO x , while operating in a higher pressure environment that is more prone to combustion instabilities.

This work focuses on the development of a lab and combustor that will be used for the next generation combustor development. The lab development includes layout and organization, facilities, measurement and instrumentation, automation of the testing process, and an imaging tool for diagnostics.

A Lean Direction Injection …

Design Of Optical Access For The Application Of Laser Doppler Velocimetry In A Low Specific Speed Centrifugal Compressor, Bryce Ashton Heckaman

Open Access Theses

The objective of this research has been to design optical access for the application of laser Doppler velocimetry (LDV) in a low specific speed centrifugal compressor. The ability to acquire non-intrusive flow measurements will provide valuable insight into tip leakage flow, secondary flow, and impeller/diffuser interactions within the centrifugal compressor. The current research facility houses a new low specific speed centrifugal compressor which design is based off a compressor that would be installed as the last stage of a high-pressure compressor.

The LDV optical access has been designed and includes two fused silica windows that are housed in stainless steel …

Optimal Control Of Unknown Nonlinear System From Inputoutput Data, Xin Jin

Open Access Theses

Optimal control designers usually require a plant model to design a controller. The problem is the controller's performance heavily depends on the accuracy of the plant model. However, in many situations, it is very time-consuming to implement the system identification procedure and an accurate structure of a plant model is very difficult to obtain. On the other hand, neuro-fuzzy models with product inference engine, singleton fuzzifier, center average defuzzifier, and Gaussian membership functions can be easily trained by many well-established learning algorithms based on given input-output data pairs. Therefore, this kind of model is used in the current optimal controller …

High Temperature Flooded Expansion For Solar Thermal Power Generation, Nelson Alexander James

Open Access Theses

Even though solar power usage has seen rapid growth over the past decade, fossil fuel generation sources are still generally a less expensive means of producing power. The Liquid-Flooded Ericsson Cycle (LFEC) was investigated as a high efficiency power cycle for reducing the cost of concentrated solar power (CSP) plants and helping to address this cost disparity. High temperature flooded expansion was identified as one of the main challenges in regards to utilizing the LFEC as a power cycle. Thermodynamic models were developed to help assess the performance of the LFEC and a load stand was constructed to test a …

Integration And Implementation Of High-Voltage Energy Storage Sub-System For A Parallel-Through-The-Road Plug-In Hybrid Electric Vehicle, Bilwa A. Jadhav

Open Access Theses

With research showing an alarming rate of increase in global warming and thus causing dangerous instabilities in the weather, a strong push has been initiated to reduce greenhouse gas emissions. Transportation being one of the top offenders in greenhouse gas emissions, has led the drive for improving the efficiency of the modern automobile. One of the current strategies for reducing the emissions produced by the transportation sector is hybrid vehicles powered from both a fuel such as gasoline, diesel, or hydrogen; and electricity. This merger has proven to be effective at decreasing harmful emissions including, carbon dioxide (CO 2 ) …

Fundamental Design Principles Of Novel Mems Based "Landau" Switches, Sensors, And Actuators : Role Of Electrode Geometry And Operation Regime, Ankit Jain

Open Access Dissertations

Microelectromechanical systems (MEMS) are considered as potential candidates for "More-Moore" and "More-than-Moore" applications due to their versatile use as sensors, switches, and actuators. Examples include accelerometers for sensing, RF-MEMS capacitive switches in communication, suspended-gate (SG) FETs in computation, and deformable mirrors in optics. In spite of the wide range of applications of MEMS in diverse fields, one of the major challenges for MEMS is their instability. Instability divides the operation into stable and unstable regimes and poses fundamental challenges for several applications. For example: Tuning range of deformable mirrors is fundamentally limited by pull-in instability, RF-MEMS capacitive switches suffer from …

High Fidelity Simulations Of Electrokinetic Phenomena In Microfluidic Devices, Qian Li

Open Access Dissertations

Electroosmotic flow with electrokinetic effects is the primary method of fluid handling in micro-total analysis systems. Under external applied electric fields, electrokinetic micro-devices allow for innovative functionality in a wide range of microfluidic applications including sample injection, separation, rapid micromixing, and miniaturized chemical and biochemical analysis and detection. This dissertation focuses on simulations of two electrokinetic phenomena, isotachophoresis (ITP) and electrokinetic instability (EKI). A set of coupled governing equations including the incompressible Naiver-Stokes equations, Nernst-Planck transport equations and a charge conservation equation are solved in the simulation. A multiblock in-house solver based on high-order finite difference schemes is developed to …

Novel Energy Efficient Electrohydraulic Steer-By-Wire Technology, Naseem Daher

Open Access Dissertations

Improving energy efficiency, productivity, safety, and comfort of mobile machines is of utmost priority to original equipment manufacturers, suppliers, and consumers given the escalating fuel prices and increased awareness to the environment and workplace hazards. A major breakthrough in the realm of high power motion control is pump displacement controlled (DC) actuation, which does away with hydraulic valves for motion control and uses a variable displacement pump as both a flow source and final control element, thus eliminating throttling losses associated with hydraulic control valves. This work deals with researching and implementing DC technology for realizing the steering function of …

Detailed Computational Modeling Of Laminar And Turbulent Sooting Flames, Adhiraj Dasgupta, Somesh Roy, Daniel C. Haworth

Mechanical Engineering Faculty Research and Publications

This study reports development and validation of two parallel flame solvers with soot models based on the open-source computation fluid dynamics (CFD) toolbox code OpenF0AM. First, a laminar flame solver is developed and validated against experimental data. A semi-empirical two-equation soot model and a detailed soot model using a method of moments with interpolative closure (MOMIC) are implemented in the laminar flame solver. An optically thin radiation model including gray soot radiation is also implemented. Preliminary results using these models show good agreement with experimental data for the laminar axisymmetric diffusion flame studied. Second, a turbulent flame solver is developed …

Determining Annoyance Thresholds Of Tones In Noise, Jennifer M. Francis, Joonhee Lee, Lily M. Wang

Durham School of Architectural Engineering and Construction: Faculty Publications

Building services equipment often produces noise signatures with significant tones in them that can lead to complaints in the built environment. Previous studies have investigated prominence levels of assorted tonal frequencies, but it is still unclear what prominence of the tones across varying tonal frequencies can lead to human annoyance. This project seeks to apply two different methods towards defining annoyance thresholds of tones in noise at two tonal frequencies: 125 Hz and 500 Hz. In the first, subjects are asked to perform a task, while exposed to ten minutes of a broadband noise spectrum with a specific level of …

An Experimental Fatigue And Finite Element Study Of A Welded Joint Of A Snowplow Blade, George Ernest Selburg

Master's Theses (2009 -)

This study describes a method to evaluate the fatigue life of a welded joint of a snowplow. Fatigue specimens were then fabricated, which simulated the joint and its loading characteristics. The joint in the specimens were characterized by measuring the geometry of the weld and the hardness of the parent material, weld material, and heat affected zone. It was determined that the fatigue crack that developed in the joint was exposed to mode I fracture forces in the normal plane of the crack. The specimens were then tested in a hydraulic closed looped system to determine the mechanism of fatigue …

An Investigation Of The Effect Of Direct Metal Deposition Parameters On The Characteristics Of The Deposited Layers, Tarak A. Amine, Joseph William Newkirk, Frank W. Liou

Materials Science and Engineering Faculty Research & Creative Works

Multilayer direct laser deposition (DLD) is a fabrication process through which parts are fabricated by creating a molten pool into which metal powder is injected as particles. During fabrication, complex thermal activity occurs in different regions of the build; for example, newly deposited layers will reheat previously deposited layers. The objective of this study was to provide insight into the thermal activity that occurs during the DLD process. This work focused on the effect of the laser parameters of newly deposited layers on the microstructure and mechanical properties of the previously deposited layers in order to characterize these effects to …

A Novel Microgrid Demand-Side Management System For Manufacturing Facilities, Terance Jerome Harper

Open Access Theses

Thirty-one percent of annual energy consumption in the United States occurs within the industrial sector, where manufacturing processes account for the largest amount of energy consumption and carbon emissions. For this reason, energy efficiency in manufacturing facilities is increasingly important for reducing operating costs and improving profits. Using microgrids to generate local sustainable power should reduce energy consumption from the main utility grid along with energy costs and carbon emissions. Also, microgrids have the potential to serve as reliable energy generators in international locations where the utility grid is often unstable.

For this research, a manufacturing process that had approximately …

Articulated Spine For A Robot To Assist Children With Autism, Brandon M. Norton

Theses and Dissertations

Autism spectrum disorder (ASD) affects about 1.5 million individuals in the US alone. The consequences of ASD affect families, caregivers, and social structures. This thesis adds to a growing group of people performing research on mitigating the effects of autism through robotics. Children with ASD tend to interact with robots more easily than with other humans. The goal of robotic therapy is not to help children interact with robots, but to generalize the behavior to humans. An articulated spine is a key to human emotional expression through shaping, weight shifting, and flow. Despite this importance, this feature is all but …

A Computational Hybrid Method For Self-Intersection Free Offsetting Of Cad Geometry, Garrett Clark Bodily

Theses and Dissertations

Surface offsetting is a valuable tool used in Computer Aided Design (CAD). An offset surface is a collection of points that are at a constant distance from another surface. An offset surface is created in CAD by selecting a surface and then specifying the distance that the surface is to be offset. If a surface is selected and a distance of D is specified, then the resulting offset surface should always be distance D from the original surface. The surface offset tool can be used for many applications. Modeling of composites or other layered manufacturing processes rely heavily on offset …

Implementation Of Analytical Fatigue Models Into Opensim To Predict The Effects Of Fatigue On Anterior Cruciate Ligament Loading, Michael A. Samann

Mechanical & Aerospace Engineering Theses & Dissertations

The anterior cruciate ligament (ACL) provides stability to the knee joint while performing activities such as a side step cut. Neuromuscular fatigue, a reduction in muscle force producing capabilities, alters lower extremity mechanics while performing a side step cut and may increase the risk of ACL injury, particularly in females. Musculoskeletal modeling allows for the measurement of muscle forces, which are difficult to measure in-vivo. Therefore, musculoskeletal modeling, may improve our understanding of the effects of neuromuscular fatigue on muscle force production and loading of the ACL. Therefore, the purpose of this study was to develop a musculoskeletal model which …

Meshless Mechanics And Point-Based Visualization Methods For Surgical Simulations, Rifat Aras

Computational Modeling & Simulation Engineering Theses & Dissertations

Computer-based modeling and simulation practices have become an integral part of the medical education field. For surgical simulation applications, realistic constitutive modeling of soft tissue is considered to be one of the most challenging aspects of the problem, because biomechanical soft-tissue models need to reflect the correct elastic response, have to be efficient in order to run at interactive simulation rates, and be able to support operations such as cuts and sutures.

Mesh-based solutions, where the connections between the individual degrees of freedom (DoF) are defined explicitly, have been the traditional choice to approach these problems. However, when the problem …

Experimental And Numerical Investigation Of The Mechanism Of Blast Wave Transmission Through A Surrogate Head, Yi Hua, Praveen Akula, Linxia Gu, Jeff Berg, Carl A. Nelson

Department of Mechanical and Materials Engineering: Faculty Publications

This work is to develop an experiment-validated numerical model to elucidate the wave transmission mechanisms through a surrogate head under blast loading. Repeated shock tube tests were conducted on a surrogate head, i.e., water-filled polycarbonate shell. Surface strain on the skull simulant and pressure inside the brain simulant were recorded at multiple locations. A numerical model was developed to capture the shock wave propagation within the shock tube and the fluid-structure interaction between the shock wave and the surrogate head. The obtained numerical results were compared with the experimental measurements. The experiment-validated numerical model was then used to further understand …

Aerodynamic Study Of Forces Due To Wind Velocity And Angle Of Attack On Parabolic Solar Troughs, Brian Northshield

Doctoral Dissertations and Master's Theses

Scant literature exists of the atmospheric effects on parabolic solar troughs. The technology is relatively new, so supporting studies by consequence are as well.

This study examines the effects of wind at various speeds, with various angles of attack on parabolic solar troughs. This begins by picking up on previous study, corroborating previously found data, then introduces new angles of attack. The model includes the presence of the solar tube where other studies omit.

The purpose of this study is to build a data set which is useful for structural consideration. During the course of this study, it was found …