Mechanical Engineering Commons^™

Impact Of Fracture Spacing And Mechanical Parameter Anisotropy On Fracture Width In Horizontal Wells In Shales, Deepak Gokaraju

Masters Theses

"The success of economically viable production of oil and gas from ultra-low permeability shale reservoirs depends on the creation of an extensive fracture network through hydraulic fracture stimulation. Multiple hydraulic fractures are created simultaneously in each stage to increase the surface area of contact between the wellbore and reservoir. The spacing between fractures is an important component to consider when developing an optimum stimulation design. An important aspect of shale rock properties is that shales are inherently anisotropic with a horizontal plane of isotropy (transversely isotropic) due to their finely layered structure. This study aims to provide an insight into …

Educational Programmes For Spatial Information Sciences In The Technological University Of Dublin, William Prendergast, Eamonn Murphy, Audrey Martin, Avril Behan

Conference papers

The ever increasing spatial information needs of society, the rapid development of new surveying technologies, and the global demand for appropriately qualified surveyors, have triggered a radical re-evaluation of geomatics education worldwide. Significant enhancements have been made to the educational programmes in the spatial information science discipline in the Technological University of Dublin’s (DIT) during the last decade including the provision of a BSc in Geomatics and various masters’ programmes to cater for the increasingly specialised needs of the Geographic Information sector in Ireland.

Bio-Inspired Flow Sensing For Underwater Guidance And Navigation, Levi Devries

Link Foundation Ocean Engineering and Instrumentation Fellowship Reports

Stream-dwelling fish and aquatic mammals have an innate ability to navigate often-tumultuous environments with impressive precision, a highly desirable trait for underwater vehicle applications. For example, trout use their lateral line to sense vortices shed by an upstream obstacle and slalom between the vortices to reduce energy expenditure compared to free-stream swimming [3]. Moreover, harbor seals can use their whiskers to follow the trail of flow disturbances created in the wake of an object that has passed minutes before [4]. Recent developments in materials science have produced sensors that can measure local flow velocity similar to seal whiskers, and integration …

Biomechanical Strain As A Trigger For Pore Formation In Schlemm’S Canal Endothelial Cells, Sietse T. Braakman, Ryan M. Pedrigi, A. Thomas Read, James A. E. Smith, W. Daniel Stamer, C. Ross Ethier, Darryl R. Overby

Department of Mechanical and Materials Engineering: Faculty Publications

The bulk of aqueous humor passing through the conventional outflow pathway must cross the inner wall endothelium of Schlemm’s canal (SC), likely through micron-sized transendothelial pores. SC pore density is reduced in glaucoma, possibly contributing to obstructed aqueous humor outflow and elevated intraocular pressure (IOP). Little is known about the mechanisms of pore formation; however, pores are often observed near dome-like cellular outpouchings known as giant vacuoles (GVs) where significant biomechanical strain acts on SC cells. We hypothesize that biomechanical strain triggers pore formation in SC cells. To test this hypothesis, primary human SC cells were isolated from three non-glaucomatous …

Altered Mechanobiology Of Schlemm’S Canal Endothelial Cells In Glaucoma, Darryl R. Overby, Enhua H. Zhou, Rocio Vargas-Pinto, Ryan M. Pedrigi, Rudolf Fuchshofer, Sietse T. Braakman, Ritika Gupta, Kristin M. Perkumas, Joesph M. Sherwood, Amir Vahabikashi, Quynh Dang, Jae Hun Kim, C. Ross Ethier, W. Daniel Stamer, Jeffrey J. Fredberg, Mark Johnson

Department of Mechanical and Materials Engineering: Faculty Publications

Increased flow resistance is responsible for the elevated intraocular pressure characteristic of glaucoma, but the cause of this resistance increase is not known. We tested the hypothesis that altered biomechanical behavior of Schlemm’s canal (SC) cells contributes to this dysfunction. We used atomic force microscopy, optical magnetic twisting cytometry, and a unique cell perfusion apparatus to examine cultured endothelial cells isolated from the inner wall of SC of healthy and glaucomatous human eyes. Here we establish the existence of a reduced tendency for pore formation in the glaucomatous SC cell—likely accounting for increased outflow resistance—that positively correlates with elevated subcortical …

Extracting Continuum-Like Deformation And Stress From Molecular Dynamics Simulations, Lili Zhang, John Jasa, George Gazonas, Antoine Jerusalem, Mehrdad Negahban

Department of Mechanical and Materials Engineering: Faculty Publications

We present methods that use results from molecular dynamics (MD) simulations to construct continuum parameters, such as deformation gradient and Cauchy stress, from all or any part of an MD system. These parameters are based on the idea of minimizing the difference between MD measures for deformation and traction and their continuum counterparts. The procedures should be applicable to non-equilibrium and inhomogeneous systems, and to any part of a system, such as a polymer chain. The resulting procedures provide methods to obtain first and higher order deformation gradients associated with any subset of the MD system, and associated expressions for …

Polymer Aggregation Correlated Transition From Schottky-Junction To Bulk Heterojunction Organic Solar Cells, Bin Yang, Zhengguo Xiao, Jinsong Huang

Department of Mechanical and Materials Engineering: Faculty Publications

The fullerene-based organic Schottky-junction solar cells have recently attracted intensive research interest because of their unique electrical performance, such as significant photocurrent generation from excitons created in fullerenes and large open-circuit voltage (V_OC) output induced by high Schottky-barrier height between the anode and the fullerene acceptor. This manuscript reports another remarkably appealing advantage that the fullerene-based Schottky-junction solar cells are more stable than the bulk heterojunction counterparts. The better stability is likely due to mitigative polymer photo-oxidation and/or little morphological change of active film in the aged Schottky-junction devices. The transition from Schottky-junction to bulk heterojunction appears at …

Numerical Simulations Of Dynamic Behavior Of Polyurea Toughened Steel Plates Under Impact Loading, Chien-Chung Chen, Daniel G. Linzell

Department of Civil and Environmental Engineering: Faculty Publications

The objective of the work discussed herein is to develop a nonlinear 3D finite element model to simulate dynamic behavior of polyurea toughened steel plates under impact loading. Experimental and numerical work related to model development are presented. Material properties are incorporated into numerical models to account for strain-rate effects on the dynamic behavior of polyurea and steel. One bare steel plate and four polyurea toughened steel plates were tested under impact loading using a pendulum impact device. Displacement time-history data from experimental work was used to validate the numerical models. Details on material model construction, finite element model development, …

Comparison Of Magnetic Probe Calibration At Nano And Millitesla Magnitudes, Ryan A. Pahl, Joshua L. Rovey, David Pommerenke

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Magnetic field probes are invaluable diagnostics for pulsed inductive plasma devices where field magnitudes on the order of tenths of tesla or larger are common. Typical methods of providing a broadband calibration of Ḃ probes involve either a Helmholtz coil driven by a function generator or a network analyzer. Both calibration methods typically produce field magnitudes of tens of microtesla or less, at least three and as many as six orders of magnitude lower than their intended use. This calibration factor is then assumed constant regardless of magnetic field magnitude and the effects of experimental setup are ignored. This work …

Adaptive Control Of Uncertain Systems With Gain Scheduled Reference Models And Constrained Control Inputs, Mehrdad Pakmehr, Tansel Yucelen

Mechanical and Aerospace Engineering Faculty Research & Creative Works

This paper develops a new state feedback model reference adaptive control approach for uncertain systems with gain scheduled reference models in a multi-input multi-output (MIMO) setting with constrained control inputs. A single Lyapunov matrix is computed for multiple linearization of the nonlinear closed loop gain scheduled reference system, using convex optimization tools. This approach guarantees stability of the closed loop gain scheduled reference model. Adaptive state feedback control architecture is then developed, and its stability is proven for the case with constrained control inputs. The resulting closed-loop system is shown to have bounded solutions with bounded tracking error, with the …

Thermal-Electromagnetic Analysis Of Infrared Antennas, Edward C. Kinzel, Brian Slovick, James Ginn, Brian Lail, Glenn Boreman

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Antenna-coupled Metal-Oxide-Metal (MOM) diodes have been demonstrated for sensing and proposed for energy harvesting at THz, infrared, and even visible frequencies. The design of the antenna allows engineering of the response of the device with respect to polarization, wavelength and angle of incidence. The classic understanding of the antenna coupled MOM diode is that the electric field generated by the antenna causes electrons to tunnel through the barrier oxide. This is supported by the fact that when the oxide separates metals with different work functions, a properly polarized field can produce an asymmetric tunnel current under zero bias. Losses in …

Verifiable Frequency-Limited Adaptive Control Performance Based On Linear Matrix Inequalities, Mario Luca Fravolini, Tansel Yucelen, Daniel Wagner, Ali Albattat, Paolo Valigi

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Adaptive controllers are often criticized for the lack of clear and easy verification procedures that relate design parameters to time domain performance especially during transients. For this reason, it is a challenge to rigorously certify existing adaptive control algorithms. To that end, we propose a validation framework where stability and performance requirements are formulated in terms of Linear Matrix Inequalities. This brings the advantage that adaptive controller design and verification can be analyzed and optimized via the solution of a convex optimization whose objective is to guarantee the evolution of the error components within an a-priori specified domain. This approach …

The Effect Of Different Rollover Conditions Of The Vibrator On Human Injury, Qin Li, Hang Liu, Zhiqiang Huang, Yaping Ding, Xiaoping Du

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Vibrator, as a crucial vehicle of oil and gas exploration, is challenged by the complex terrains. The probability of rollover accident is therefore high in bumpy terrain in which the drivers' life is seriously threatened. Finite element numerical analysis was used to study the injury of the driver's head, neck and chest in the rollover accidents of domestic KZ-28 type vibrator on different conditions. The injuries of three parts were evaluated based on the human injury criteria. Driver's safety on different rollover conditions was comparatively analyzed. The results indicated that the injury degree of human head caused by vibrator rollover …

Decomposition Of Ionic Liquid Ferrofluids For Multi-Mode Spacecraft Propulsion, Steven P. Berg, Brynne Coleman, Joshua L. Rovey

Mechanical and Aerospace Engineering Faculty Research & Creative Works

Ionic liquid ferrofluids based on mixtures of [Emim][EtSO4] and [Bmim][NO3] fuels and hydroxylammonium nitrate oxidizer were synthesized by adding iron oxide nanoparticles. The resulting propellants were then tested for decomposition capability. Spot plate testing indicated that the temperature required to initiate rapid decomposition dropped from 115 °C to 75 °C with a 30% by weight addition of iron oxide for the [Bmim][NO3] propellant. Adding more iron oxide resulted in an increase in onset temperature. The [Emim][EtSO4] propellant had a much lower decrease in onset temperature, bottoming out at 90 °C. Batch reactor tests under vacuum showed that 10% addition of …

Predicting Pressure Distribution Between Transfemoral Prosthetic Socket And Residual Limb Using Finite Element Analysis, Rajesh Surapureddy

UNF Graduate Theses and Dissertations

In this study, a non-linear Finite Element (FE) model was created and analyzed to determine the pressure distribution between the residual limb and the prosthetic socket of a transfemoral amputee. This analysis was performed in an attempt to develop a process allowing healthcare providers and engineers to simulate the fit and comfort of transfemoral prosthetics to reduce the number of re-fittings needed for the amputees. The analysis considered the effects of interference due to insertion of the limb into the prosthesis, referred to as donning, and also the effects due to the body weight of the amputee. A non-linear finite …

Probabilistic Engineering Analysis And Design Under Time-Dependent Uncertainty, Zhen Hu

Doctoral Dissertations

"Time-dependent uncertainties, such as time-variant stochastic loadings and random deterioration of material properties, are inherent in engineering applications. Not considering these uncertainties in the design process may result in catastrophic failures after the designed products are put into operation. Although significant progress has been made in probabilistic engineering design, quantifying and mitigating the effects of time-dependent uncertainty is still challenging. This dissertation aims to help build high reliability into products under time-dependent uncertainty by addressing two research issues. The first one is to efficiently and accurately predict the time-dependent reliability while the second one is to effectively design the time-dependent …

A Study Of Walkway Safety And Evaluation Of Tribological Test Equipment, Henry Thomas Baker

UNF Graduate Theses and Dissertations

A walkway tribometer measures the coefficient of friction between flooring material and a test foot. The value of the coefficient of friction is an indicator as to whether the flooring surface is slippery and has a propensity to cause slip and falls. This study determined that one style of tribometer, an XL Tribometer, mimics the heel-to-floor interaction of the human heel strike. High speed video footage revealed that the test foot strikes the surface and rotates so that full engagement occurs before sliding thus mimicking the affect of a human ankle. The test foot accelerates forward as would be expected …

Role Of Surface Chemistry In Nanoscale Electrokinetic Transport, Secuk Atalay

Mechanical & Aerospace Engineering Theses & Dissertations

This dissertation work presents the efforts to study the electrofluidics phenomena, with a focus on surface charge properties in nanoscale systems with the potential applications in imaging, energy conversion, ultrafiltration, DNA analysis/sequencing, DNA and protein transport, drug delivery, biological/chemical agent detection and micro/nano chip sensors.

Since the ion or molecular or particle transport and also liquid confinement in nano-structures are strongly dominated by the surface charge properties, in regards of the fundamental understanding of electrofluidics at nanoscale, we have used surface charge chemistry properties based on 2-pK charging mechanism. Using this mechanism, we theoretically and analytically showed the surface charge …

Mechanistic Identification Of Specific Force Coefficients In Endmilling Inconel 718 Under Four Cooling Strategies, Mahmood Shaman Ameen

Masters Theses

“This thesis presents the results of experimental investigations of the mechanistic identification of specific force coefficients for uncoated bull-nose and uncoated wavy-edge/bull-nose helical endmilling of Inconel 718 under emulsion, minimum quantity lubrication (MQL), cryogenic (LN₂), and combined (MQL + LN₂) cooling. Several slot milling tests were conducted on Inconel 718 workpiece block with depth of cut 1.25 mm. The cutting parameters were varied as: spindle speed, n = 250 and 750 rev/min, feedrate, f = 25–75 mm/min by using uncoated carbide bull-nose helical endmill. Also 24 peripheral milling tests were conducted on Inconel 718 workpiece block …

Computationally Efficient Representation Of Statistically Described Material Microstructure For Tractable Forming Simulations, Nicholas Landry

Honors Theses and Capstones

The purpose of this project is to reduce a large statistical distribution of metal microstructure orientations to a manageable distribution to be used in metal forming simulations. Microstructure sensitive simulations at the macro-scale are impractical, because with so many state variables associated with material microstructure data, these simulations are extremely computationally expensive.

The goal was to develop a framework to accurately model plastic material response while repre- senting the material microstructure in a more compact form, reducing 106 or more microstructure orientations to a significantly smaller statistical distribution of representative orientations. This will significantly increase the computational efficiency and make …

Gadolinia Doped Hafnia (Gd2o3- Hfo2) Thermal Barrier Coatings For Gas Turbine Applications, Satya Kiran Gullapalli

Open Access Theses & Dissertations

Thermal efficiency of the gas turbines is influenced by the operating temperature of the hot gas path components. The material used for the hot gas path components can only withstand temperature up to a certain limit. Thermal barrier coatings (TBC) provide the additional thermal protection for these components and help the gas turbine achieve higher firing temperatures. Traditionally available yttria stabilized zirconia (YSZ) TBCs have a limitation up to 1200 C due to their phase transformation. The present work focuses on gadolinia based hafnia (GSH) TBCs to study their potential to replace the YSZ coatings. Different compositions of gadolinia doped …

Characterizing Cryogenic Propellant Flow Behavior Through A Cavitating Venturi In Comparison To Alternative Flow Control Mechanisms, Marjorie Adele Ingle

Open Access Theses & Dissertations

The work detailed is an investigation of the use of a cavitating venturi as both a flow control and metering device. This was achieved through the combination of actual experimentation and numerical modeling of the fluid behavior of both liquid water and liquid methane as it passes through the test article designed, developed, and validated here within this study. The discharge coefficient of the cavitating venturi was determined through weigh flow calibration testing to determine an average mass flow rate. Turbine flow meter flow rate readings were used as a point of comparison and the discharge coefficient was computed. The …

Fabrication Of A Nickel-Based Superalloy In Electron Beam Melting And Process Improvements Using Thermal Feedback From A Multi-Wavelength Pyrometer, Jonathan Minjares

Open Access Theses & Dissertations

The focus of this research was to fabricate parts composed of a nickel-based superalloy containing high levels of aluminum and titanium (NSAT) by using electron beam melting (EBM) additive manufacturing (AM) technology and utilizing thermal feedback from a multi-wavelength pyrometer to perform process improvements leading to near defect-free parts. EBM is an AM technology that utilizes metal powder to fabricate parts in layer-by-layer manner. A multi-wavelength pyrometer was implemented in an Arcam S12 (Arcam AB, Sweden) EBM system to observe and record surface temperatures throughout fabrication. Temperature data from the EBM system and the multi-wavelength pyrometer were graphed using MATLAB …

Design And Evaluation Of A High Temperature/Pressure Supercritical Carbon Dioxide Direct Tubular Receiver For Concentrating Solar Power Applications, Jesus Daniel Ortega

Open Access Theses & Dissertations

This work focuses on the development of a solar power thermal receiver for a supercritical-carbon dioxide (sCO2), Brayton power-cycle to produce ~1 MWe. Closed-loop sCO2 Brayton cycles are being evaluated in combination with concentrating solar power to provide higher thermal-to-electric conversion efficiencies relative to conventional steam Rankine cycles. High temperatures (923 - 973 K) and pressures (20 - 25 MPa) are required in the solar receiver to achieve thermal efficiencies of ~50%, making concentrating solar power (CSP) technologies a competitive alternative to current power generation methods. In this study, the CSP receiver is required to achieve an outlet temperature of …

Design And Development Of Implantable And Remote Controlled Distraction Osteogenesis Device For Limb Lengthening Practice In Children, Mario Eduardo Rodriguez De La O

Open Access Theses & Dissertations

Recent technology improvements have been positively affecting medical industry in recent years since procedures and equipment are more precise and reliable. Nevertheless, there are still surgical procedures and medical devices that not fully address specific needs according to medical experts. One of those necessities is focused on options available for children patients when subjected to a surgical procedure named distraction osteogenesis. In general, distraction osteogenesis is performed when skeletal deformities need to be corrected or when bone lengthening is required, typically a mechanism is utilized to elongate bone at a controlled rate. The existing osteodistraction methods for limb lengthening and …

Characterization Of High-Purity Niobium Structures Fabricated Using The Electron Beam Melting Process, Cesar Adrian Terrazas

Open Access Theses & Dissertations

Additive Manufacturing (AM) refers to the varied set of technologies utilized for the fabrication of complex 3D components from digital data in a layer-by-layer fashion. The use of these technologies promises to revolutionize the manufacturing industry. The electron beam melting (EBM) process has been utilized for the fabrication of fully dense near-net-shape components from various metallic materials. This process, catalogued as a powder bed fusion technology, consists of the deposition of thin layers (50 - 120µm) of metallic powder particles which are fused by the use of a high energy electron beam and has been commercialized by Swedish company Arcam …

An Experimental Investigation On Liquid Methane Convection And Boiling In Rocket Engine Cooling Channels, Abraham Trujillo

Open Access Theses & Dissertations

In the past decades, interest in developing hydrocarbon-fueled rocket engines for deep spaceflight missions has continued to grow. In particular, liquid methane (LCH4) has been of interest due to the weight efficiency, storage, and handling advantages it offers over several currently used propellants. Deep space exploration requires reusable, long life rocket engines. Due to the high temperatures reached during combustion, the life of an engine is significantly impacted by the cooling system's efficiency. Regenerative (regen) cooling is presented as a viable alternative to common cooling methods such as film and dump cooling since it provides improved engine efficiency. Due to …

Nanometric Structure-Property Relationship In Hafnium Oxide Thin Films Made By Sputter-Deposition, Mirella Vargas

Open Access Theses & Dissertations

Hafnium oxide (HfO2) is technologically an important material, which exhibits a unique set of properties such as a high dielectric constant (k~25) and wide band gap (~5.7 eV) which make this material attractive in the fields of microelectronics and optoelectronics. HfO2 has become the leading candidate to replace SiO2 dielectrics in gate oxides due to a higher permittivity and reportedly lower electron tunneling effects. HfO2 exhibits various polymorphs; the thermodynamic stability and phase existence depends on the temperature and pressure conditions. In addition, the controlled growth and manipulation of specific HfO2 crystal structures at the nanoscale dimensions is the driving …

Modeling And Simulation Of A Lead-Free Active Structural Fiber For Multifunctional Composites, Linda Vera

Open Access Theses & Dissertations

Piezoelectric materials are widely used in a many areas of science and technology due to their unique electromechanical properties. The transformation of mechanical energy into electrical energy and vice versa caused by the piezoelectric effect has led to the development of piezoelectric sensor devices and actuators used in accelerometers, pressure and vibration meters, micropositioning devices, ultrasound generators, structural health monitoring, etc.

The most used piezoelectric material to this day is lead zirconate titanate PbZrO3-PbTiO3 (PZT) because of its high piezoelectric coefficient and Curie temperature, which allows it to be used in a more wide variety of applications. However, the commercial …

The Interfacial Fracture Of Bonded Materials And Composites, Kai Zhao

Open Access Theses & Dissertations

Adhesive bonding and composite materials have been widely used in manufacturing industry. Failure results from the weakest link in a structure and this is often the interface between two materials. In case of composites, it becomes the fiber and matrix interface. In case of bonded polymers, the bonding line is the interface. This Dissertation is focused on the interfacial fracture of bonded materials and composites. First, a systematic experimental investigation on adhesive bonding strengths of polymer/polymer and polymer/metal joints was conducted and the experimental results were compared with other researchers' work. Then, a modified short-beam shear approach is developed to …