Mechanical Engineering Commons^™

A Degradation Function Consistent With Cocks–Ashby Porosity Kinetics, John A. Moore

Mechanical Engineering Faculty Research and Publications

The load carrying capacity of ductile materials degrades as a function of porosity, stress state and strain-rate. The effect of these variables on porosity kinetics is captured by the Cocks–Ashby model; however, the Cocks–Ashby model does not account for material degradation directly. This work uses a yield criteria to form a degradation function that is consistent with Cocks–Ashby porosity kinetics and is a function of porosity, stress state and strain-rate dependence. Approximations of this degradation function for pure hydrostatic stress states are also explored.

Improved A-B10C2+XHY/Si P-N Heterojunction Performance After Neutron Irradiation, George Peterson, Qing Su, Yongqiang Wang, Natale J. Ianno, Peter Dowben, Michael Nastasi

Department of Mechanical and Materials Engineering: Faculty Publications

The impact of neutron irradiation, in the energy range of ~0.025 eV, on amorphous semiconducting partially dehydrogenated boron carbide (a-B₁₀C_2+xH_y) on silicon p-n heterojunction diodes was investigated. The heterojunction devices were created by synthesizing a-B₁₀C_2+xH_y via plasma enhanced chemical vapor deposition on n-type silicon. Unlike many electronic devices, the performance of the a-B₁₀C_2+xH_y heterojunction diode improved with neutron irradiation, in spite of the large neutron cross section of ¹⁰B. There is also increased charge carrier lifetime of more than …

Tissue Stresses In Stented Coronary Arteries With Different Geometries: Effect Of The Relation Between Stent Length And Lesion Length, Xiang Shen, Song Ji, Yong-Quan Deng, Hong-Fei Zhu, Jia-Bao Jiang, Linxia Gu

Department of Mechanical and Materials Engineering: Faculty Publications

In-stent restenosis after stent deployment remains an obstruction in the long-term benefits of stenting. This study sought to investigate the influence of the relation between stent length and lesion length on the mechanics of the arterial wall with different geometries, including straight and tapered vessels. Results showed that when the length of the stent was longer than the lesion length, the maximum stress in plaque and vessel increased as the length of stent increased. When the length of the stent was shorter than the lesion length, the vessel stress induced by stent inflation was lower; both ends of the stenosis …

Experimental Measurement Of Dolphin Thrust Generated During A Tail Stand Using Dpiv, Frank E. Fish, Terrie M. Williams, Erica Sherman, Yae Eun Moon, Vicki Wu, Timothy Wei

Department of Mechanical and Materials Engineering: Faculty Publications

Estimation of force generated by dolphins has long been debated. The problem was that indirect estimates of force production for dolphins resulted in low values that could not be validated. Bubble digital particle image velocimetry (DPIV) measured hydrodynamic force production for swimming dolphins and demonstrated high force production. To validate the bubble DPIV and reconcile force production measurements, two bottlenose dolphins (Tursiops truncatus) performing tail stands were measured with bubble DPIV. Microbubbles were generated from a finely porous hose and compressed air source. Displacement of the bubbles by the propulsive motions of the dolphin was tracked with a …

Study Of Asymmetry Configuration Effects On Plate Heat Exchanger Performance, Pearachad Chartsiriwattana

Chulalongkorn University Theses and Dissertations (Chula ETD)

Plate heat exchanger is wildly used in engineering application. Previous studies indicated that flow profile effects to plate heat exchanger overall heat transfer coefficient with various factors that manipulate flow profile. This study aims to observe the effect of manipulation flow by creating non-uniform cross-section area along with the flow by applied asymmetry configuration to plate heat exchanger. The experimental results categorize into two groups. The first group is an asymmetric configuration that enhances the overall heat transfer coefficient by 6.54% compared to symmetric configuration due to promoting heat convection. The other group is an asymmetric configuration that ineffective to …

Erosion Degradation Characteristics Of A Linear Electro-Hydrostatic Actuator Under A High-Frequency Turbulent Flow Field, Yuan Li, Shaoping Wang, Mileta M. Tomovic, Chao Zhang

Engineering Technology Faculty Publications

The paper proposes a performance degradation analysis model based on dynamic erosion wear for a novel Linear Electro-Hydrostatic Actuator (LEHA). Rather than the traditional statistical methods based on degradation data, the method proposed in this paper firstly analyzes the dominant progressive failure mode of the LEHA based on the working principle and working conditions of the LEHA. The Computational Fluid Dynamics (CFD) method, combining the turbulent theory and the micro erosion principle, is used to establish an erosion model of the rectification mechanism. The erosion rates for different port openings, under a time-varying flow field, are obtained. The piecewise linearization …

Developing A 3d In Vitro Model By Microfluidics, Hung-Ta Chien

Dissertations and Theses

In vitro tissue models play an important role in providing a platform that mimics the realistic tissue microenvironment for stimulating and characterizing the cellular behavior. In particular, the hydrogel-based 3D in vitro models allow the cells to grow and interact with their surroundings in all directions, thus better mimicking in vivo than their 2D counterparts. The objective of this thesis is to establish a 3D in vitro model that mimics the anatomical and functional complexity of the realistic cancer microenvironment for conveniently studying the transport coupling in porous tissue structures. We pack uniform-sized PEGDA-GelMA microgels in a microfluidic chip to …

Smart Prismatic Louver Technology For Enhanced Daylighting And Management Of Thermal Loads In Green Buildings, Michael Alva

Dissertations and Theses

Abstract

Two significant design strategies for mitigating building energy consumption are daylight redirection and solar energy harvesting. Good daylighting implementation enhances the amount of useful natural light within a space, thereby offsetting the need for electric lighting. Solar energy harvesting systems can mitigate energy costs from mechanical systems by managing incoming thermal loads or capturing solar energy that can be used to supplement thermal systems in the building. While there are many available façade-based technologies that can perform daylighting or solar thermal energy harvesting, there remains a limitation in available systems that can perform both simultaneously. The proposed Liquid Filled …

An Integrated Closed Convergent System For Optimal Extraction Of Head-Driven Tidal Energy, Michelle Ann Vieira

UNF Graduate Theses and Dissertations

As the demands for energy increased with the global increase in population, there is a need to create and invest in more clean and renewable energy sources. Energy derived from the movement of the tides is an ancient concept that is currently being harnessed in a handful of large tidal range locations. However, the need to move from fossil fuel driven energy sources to those that are clean and non-polluting is a priority for a sustainable future. Globally, hydropower potential is estimated to be more than 16,400-Terawatt hours annually. Given that the electricity consumption worldwide was at 15,068-Terawatt hours in …

Analysis Of Aluminum-Air Battery By Physics-Based Mathematical Model, Chong Zhou

Graduate Research Theses & Dissertations

The demand of electrical energy system is increasing rapidly these days for diverse applications from portable electronics and electrical vehicles to grid-scale energy storage. Lithium-ion battery has been utilized for most of those applications, but due to high cost (about $600/ kWh) and lower energy density (0.37 kWh/kg), the advent of low cost and high performing battery system is required. In this study, we will revisit aluminum-air battery as a promising system which has excellent features such as high energy density of 2.8 kWh/kg, low cost, and safe in nature, but it was abandoned due to challenging issues. One of …

3d Global Acceleration Estimation Using Inertial Measurement Unit For Biomechanical Research, Revanth Raghuram Konda

Graduate Research Theses & Dissertations

The effects of mechanical vibrations on the body of a driver in off-road vehicles such as mining vehicles have become one of the intriguing research topics. To reduce the injuries of the operator of an off-road vehicle where vibrations of high magnitude occur, an indepth study of the nature of these vibrations must be done. The first step towards this objective is the correct estimation of acceleration of the vehicle by taking into consideration all the translational and rotational motion. The main goal of this study is the estimation of acceleration of an off-road vehicle in 3D space using an …

Surface Modification Of Titanium For Hard-Tissue Engineering Applications, Murali Krishna Duvvuru

Graduate Research Theses & Dissertations

Titanium (Ti) and its alloys are widely used in dental and orthopedic applications due to their advantages such as biocompatibility, excellent corrosion resistance and mechanical properties like low Young’s modulus, low density and high strength as compared to other metallic implants. However, lack of interaction with host tissue (e.g. bioinertness), higher modulus of elasticity as compared to that of bone and resultant stress shielding cause fibrous tissue formation around the implant where the interaction with tissue is minimized. These will eventually cause the implant loosening and revision surgery is needed. Surface modification of Ti by increasing surface roughness and/or incorporation …

Simulation Of An Ethylene Flame With Turbulence, Soot And Radiation Modeling, Santu Golder

Electronic Theses and Dissertations

This thesis will investigate soot models that are available in commercial codes. We will look at the effect of turbulence models, gravity, soot models and radiation. Simulations will be compared to Coppalle and Joyeux [1]. The flame is an ethylene air diffusion flame at a Reynolds number of 5700. Simulations show the SST turbulence model, one-step soot model and Rosseland radiation model including gravity agree well with experimental data (temperature and soot). Flamelet soot modeling from Carbonell et al. [2] and flamelet radiation modeling from Doom [3] has been incorporated and compared as well.

Shape From Focus Image Processing Approach Based 3d Model Construction Of Manufactured Part, Mitchel Wendland

University of the Pacific Theses and Dissertations

The purpose of this research is to develop a process and an algorithm to create a 3D model of the surface a part. This is accomplished using a single camera and a CNC machine as a movable stage. A gradient based focus measure operator written in MATLAB is used to process the images and to generate the surface model. The scopes of this research are image processing and surface model generation as well as verifying part accuracy. The algorithm is able to create a rough surface model of a photographed part, and with careful calibration in a limited number of …

Effect Of Process Parameters On The Surface Roughness And Mechanical Performance Of Additively Manufactured Alloy 718, Bo Ryan Whip

Browse all Theses and Dissertations

Metal additive manufacturing (AM) is a method to create complex components in a layer-by-layer process. Currently, there is a lack of understanding in the processing-structure-properties-performance relationship, particularly related to defects inherent to the AM process. This work investigates the relationship of process parameters, as-built surface roughness, and mechanical performance for nickel-based superalloy 718 built using laser powder bed fusion. The surface roughness of components built using varied processing parameters was characterized using both nondestructive and destructive measurement techniques. Finite element analysis was used to study the stress concentration on surface profiles. Statistical correlations are presented between contour processing parameters and …

Investigation Into Integrated Free-Form And Precomputational Approaches For Aerostructural Optimization Of Wind Turbine Blades, Ryan Timothy Barrett

Theses and Dissertations

A typical approach to optimize wind turbine blades separates the airfoil shape design from the blade planform design. This approach is sequential, where the airfoils along the blade span are pre-selected or optimized and then held constant during the blade planform optimization. In contrast, integrated blade design optimizes the airfoils and the blade planform concurrently and thereby has the potential to reduce cost of energy (COE) more than sequential design. Nevertheless, sequential design is commonly performed because of the ease of precomputation, or the ability to compute the airfoil analyses prior to the blade optimization. This research investigates two integrated …

Pressure Measurements Inside Multiple Cavities Of A Torque Converter And Cfd Correlation, Edward De Jesus Rivera

Dissertations, Master's Theses and Master's Reports

A torque converter was instrumented with 29 pressure transducers. The pressure transducers were located in multiple cavities. The instrumented cavities included, four transducers mounted on the impeller shell, on the channel between blades. Six transducers mounted on the pressure and suction sides on the middle streamline of a turbine blade. Another seven transducers mounted on the pressure and suction sides of the core, middle and shell streamlines of a stator blade. Seven transducers mounted on the torque converter clutch cavity. Finally, five on the cavity between the pressure plate and the turbine shell. The torque converter was part of a …

Reconstructing Insect Pursuit Flight Kinematics In The Wild, Haribabu Boddeeti

Graduate Research Theses & Dissertations

With their agile maneuvers and aerodynamic feats, flying insects continue to inspire the design, sensing, and control of unmanned aerial vehicles. Among the different behaviors that such insects perform, the mating pursuit stands out in terms of the high speeds and quick turns that each insect performs during the chase. Despite their frequent occurrence in nature, pursuit events between mating insects are rarely analyzed. This is because mating events are difficult to film in the wild or elicit in laboratory settings. The long-term goal of this research is to quantify the kinematics of flying insects in pursuit. The specific objective …

Development Of A Multi-Robot Testbed For Direct Human-Swarm Interaction, Venkata Satya Kiran Maridi

Graduate Research Theses & Dissertations

Robotic swarms are well suited for missions that involve covering large areas such as environmental monitoring, search-and-rescue operations, as well as those that require fusing information from multiple sources such as target tracking and machine inspection. However, navigating a swarm of robots effectively requires performing higher-level functions that are typically executed by humans such as commanding them to stay close and guiding them along with a preplanned route. In this context, the ability of multiple robots to stay together autonomously significantly reduces the cognitive load on a human operator. The goal of this thesis is to design and build a …

Theoretical Study Of Laser-Assisted Machining On Silicon Nitride Hollow Ceramic Cylinder Using Finite Element Method, Mudassar Hussain Ansari Mohammed

Graduate Research Theses & Dissertations

The most commonly used technique for machining ceramics is diamond grinding. It accounts for up to 75% of the manufacturing costs resulting in high cost of the product. An LED bulb offering increased brightness, energy saving and long life by using ceramic integration to LED chips costs around 10 times to a normal LED bulb. Complex geometries used in electronics, medical surgeries, aerospace, and automobile industries require the use of costly molds or powder metallurgy for low batch production which does not justify the cost. Laser Assisted Machining (LAM) is a process that uses a laser to locally heat the …

Case Study: Applying Lean Manufacturing Principles To The Prep Process Of The Hurricane Island Outward Bound School, Ben Branson

Honors Theses

This study synthesizes the author's area of education and occupational passions by applying lean manufacturing principles such as those of the Toyota Production System to the course preparation process at the Hurricane Island Outward Bound School. Over four weeks in the summer of 2017, the initial conditions were monitored and changes were implemented in both the layout of the base and the process itself, specifically the logistics portions. At the end of the season, the effectiveness of these changes were evaluated through a staff survey and comparison of evidence gathered during the summer. The time needed for prep logistics was …

Experimental Validation Of An Unscented Kalman Filter For Estimating Transient Engine Exhaust Composition With Fourier Transform Infrared Spectroscopy, David Wilson, Casey Allen

Mechanical Engineering Faculty Research and Publications

Fourier transform infrared (FTIR) spectroscopy is a prevalent technique for measuring the comprehensive chemical composition of engine emissions. However, its applicability to transient emissions is limited due to recirculation of exhaust from past engine cycles within a FTIR gas cell and nonstationarity of the infrared beam intensity. An unscented Kalman filter is developed to overcome these limitations and obtain accurate, time-resolved estimations of engine exhaust composition from FTIR measurements. Residence time distribution within the FTIR gas cell is modeled using the well-mixed assumption, while the Fourier transform of an interferogram generated from a linearly evolving, uniformly broadened absorption line is …

High Speed, Micron Precision Scanning Technology For 3d Printing Applications, Nicholas Emord

UNF Graduate Theses and Dissertations

Modern 3D printing technology is becoming a more viable option for use in industrial manufacturing. As the speed and precision of rapid prototyping technology improves, so too must the 3D scanning and verification technology. Current 3D scanning technology (such as CT Scanners) produce the resolution needed for micron precision inspection. However, the method lacks in speed. Some scans can be multiple gigabytes in size taking several minutes to acquire and process. Especially in high volume manufacturing of 3D printed parts, such delays prohibit the widespread adaptation of 3D scanning technology for quality control. The limiting factors of current technology boil …

Effects Of Milling Methods, Cooling Strategies And End-Mill Coatings On Machinability In High Speed End-Milling Of Inconel- 718 Using Carbide End-Mills, Paras Mohan Jasra

Doctoral Dissertations

“Inconel-718 superalloy is used extensively in aerospace and nuclear industries due to its excellent properties such as: high strength-to-weight ratio, ability to retain its properties at high temperature, high corrosion and creep resistance. However, Inconel-718 is characterized as a “difficult-to-cut metal”, because it poses severe problems during machining such as: high temperature at the cutting zone due to low thermal conductivity, hardening tendency at elevated temperature, high cutting forces, rapid tool wear and high chemical affinity with many cutting tools. Appropriate cooling strategies, milling methods, tool coatings and cutting speeds play important roles in addressing these problems. This research presents …

Responsiveness Comparison Between A Lift-Type And Drag-Type Rotor In Waves, Yingchen Yang, Fredrick A. Jenet, Deyanira Jimenez, Brandon Benavides, Jesus Cerda, Angel Lopez

Mechanical Engineering Faculty Publications

Our recent progress on development of a vertical-axis unidirectional rotary wave energy converter (WEC) is discussed in this work. The WEC features a vertical-axis rotor that preforms unidirectional rotation in waves. The vertical axis arrangement makes the WEC respond well to waves from any direction with no realignment needs. And, the unidirectional behavior of the rotor promises no wave frequency discrimination, which is in comparison to reciprocating WECs that employ the resonant principle and are very frequency-specific. In our earlier proof-of-concept studies, we have successfully demonstrated two types of rotor designs: a lift type employing hydrofoil blades and a drag …

Fracture Mechanics Of Heterogeneous Composites, Md Fazle Rabbi

Open Access Theses & Dissertations

The increasing application of composite materials due to their ubiquitous advance in terms of mechanical and thermal properties has brought attention to the fracture mechanics of the materials possessing heterogeneity. Recent investigations have focused on the micro- and macro-mechanism of fracture in heterogeneous composites (HCs). In this study, the fracture mechanics of the two HCs: Polymer bonded explosive (PBX) simulant and hot mixed asphalt (HMA) are evaluated on the macroscopic scale. It is an interest of Sandia National Laboratory to examine the fracture resistance of PBXs, particularly those of varying composition and subjected to aging. In this research, a batch …

Constitutive Model Development For Additive Manufacturing, Diana Berenice Montes

Open Access Theses & Dissertations

Additive manufacturing (AM) is known worldwide for revolutionizing the development of three-dimensional modeling by reducing the time and increasing the precision of parts. For Powder Bed Fusion research is necessary to reduce concerns in residual stress, porosity and cracking in AM parts. A constitutive model was created in Abaqus to validate material properties of 3D printed Al 6061. Finite element analysis was performed to investigate how properties may affect in the modification of parameters to reduce printing imperfections. Research was made as well in polylactic acid properties for material extrusion to explore its behavior for creep and relaxation. Properties were …

Design And Experimental Study Of A High Pressure And Supercritical Methane-Oxygen Burner, A S M Arifur Rahim Chowdhury

Open Access Theses & Dissertations

Directly heated supercritical oxy-fuel power cycles have potential to offer a higher thermal efficiency and lower pollutant emissions compared to existing power cycles. Recent thermodynamic analysis of the cycle performed by several groups including the UTEP-Air Liquide research team show that combustion in the vicinity of 300 bar pressure and 1000-1400 K temperature allows for relatively high system efficiencies while operating within the limit of practical combustor materials. However, the realization of directly heated supercritical power cycle requires combustion systems be designed to operate in supercritical conditions and at temperature far below the blowout limit of conventional flames (above 1500 …

Predictive Modeling On The Piezoelectric Properties Of 3d Printed Functional Nanocomposites Using The Data Analytics Approach, Md Didarul Islam

Open Access Theses & Dissertations

This paper presents research done on prediction modeling using a data analytics approach to determine various factors affecting the piezoelectric properties of the 3D printed pressure sensors. Previously, the material extrusion 3D printing technique was used to fabricate pressure sensors composed of multiwall carbon nanotubes (CNT), barium titanate (BT), and polyvinylidene fluoride (PVDF) using simple fabrication and low-cost methods. This sensor produced a voltage output of 725 mV (0.13 pC/N) which is enough for pressure sensing applications. However, a holistic study to determine impacts of all factors was not carried out in the previous model. In this study, the design …

Additive Manufacturing Of Energy Harvesting Material System For Active Wireless Mems, Victor Fernando Elicerio

Open Access Theses & Dissertations

Additive manufacturing (AM - most commonly known as 3D printing) is a fabrication method and aims to increase production efficiency while lowering costs of constructing quality components for industry application when compared to traditional machining. In addition to this, AM possesses capabilities that far exceed machining as complex geometries are achievable through an array of technologies in a wide variety of materials. The AM process begins with a computer aided design (CAD) which creates a design path for a 3D printer to follow. By following this path, components are built from bottom to top in a layer by layer fashion. …