Engineering Commons^™

Fabrication Of Sers Active Nanostructures By Femtosecond Laser Micromachining, Matthew Aaron Olson

Masters Theses

"This work investigated the surface-enhanced Raman scattering (SERS) enhancement of gold nanoparticles on femtosecond laser created nanostructures on a silicon wafer. The goal was to use the nanostructures to assemble the nanoparticles into three-dimensional aggregates and compare these enhancements to those of two dimensional aggregates. The SERS enhancement generated by the three-dimensional structures was on average 5 x 10⁴ with a high enhancement of 1.2 x 10⁵. The magnitude of this enhancement was on par with previous experiments that tested SERS enhancements on gold nanoparticles, but it did not show any significant enhancement caused by the three-dimensional nature of the …

Sandwich Structures With Advanced Facings, Cody H. Nguyen

Doctoral Dissertations

"The purpose of this research is to investigate potential advantages of two innovative designs of sandwich panels. The first design involves sandwich panels with a piece-wise thickness of the facings aiming at two possible outcomes: (I) improved the structural response, i.e. strength and stiffness, without increasing the weight of the structure or (2) reduction in the weight of the structure without a detriment to its structural response. The analysis is conducted analytically using the first-order shear deformation theory and numerically by the finite element analysis of conventional and stepped-wise sandwich panels. The applicability of the first-order shear deformation theory to …

Integrated Reliable And Robust Design, Gowrishankar Ravichandran

Masters Theses

"The objective of this research is to develop an integrated design methodology for reliability and robustness. Reliability-based design (RBD) and robust design (RD) are important to obtain optimal design characterized by low probability of failure and minimum performance variations respectively. But performing both RBD and RD in a product design may be conflicting and time consuming. An integrated design model is needed to achieve both reliability and robustness simultaneously. The purpose of this thesis is to integrate reliability and robustness. To achieve this objective, we first study the general relationship between reliability and robustness. Then we perform a numerical study …

Solar Powered Residential Hydrogen Fueling Station, Aanchal Shah

Masters Theses

"Interest towards the hydrogen fuel technology is increasing but its potential benefits will not be felt until hydrogen vehicles and the fueling infrastructure captures a substantial market share. Though there has been a rapid progress in the hydrogen fuel cell technology, a major challenge to the commercialization of fuel cell vehicles is the lack of hydrogen fueling infrastructure. The development of a commercial hydrogen fueling station is a challenge due to its high initial cost and safety concerns. Residential fueling stations provide an innovative solution to this issue since they also produce electricity and heat for the residential buildings in …

Development Of A Simple Vibration Model For Predicting The Structural Dynamics Of An Hcci Engine, Jeffery A. Massey

Doctoral Dissertations

"The hypothesis tested in this work is that the surface vibration and radiated sound of an engine operating under HCCI combustion is dominated by the free vibration response of the engine's structural components to an impulsive loading brought about by the rapid energy release of the HCCI combustion process. Recent work by the author has shown that classical vibration theory describing the dynamic response of a single-degree-of-freedom (SDOF) oscillator may capture the major characteristics of the engine surface vibrations. Through an experimental investigation of HCCI combustion engine dynamics this model has been developed further.

A band level analysis of measured …

Dynamic Ergonomic Analysis And Simulation Of Fastening Operation, Akul Joshi

Doctoral Dissertations

"Operator performing fastening operation with powered hand-tools at awkward postures is subjected to external forces that may pose a risk of developing ergonomic injuries. For design of safe workplaces and selection of tools it is necessary to identify the probable causes of discomfort by simulating the work conditions and quantifying the risk factors. An ergonomic simulator is developed to simulate the fastening operation and quantify the effects of posture and force in fastening operation. The effect of dynamic forces is analyzed using two approaches. The first approach analyzes the effect of tool vibration while the second analyzes the hand-arm system …

Effect Of Initial Conditions On Molecular Mixing In A High Schmidt-Number Rayleigh-Taylor Mixing Layer, Lakshmi Ayyappa Raghu Mutnuri

Masters Theses

"Characterizing molecular mixing in Rayleigh-Taylor instability (RTI) driven flows where the density and velocity fields are coupled is essential for developing exacting predictive models. Sensitivity of the Rayleigh Taylor mixing layer to initial conditions is a topic that is being explored extensively in interests of accurate turbulent mix model development and its direct consequence in various applications like design of inertial confinement fuel capsule and atmospheric modeling. As part of the current work, an experimental investigation of the effect of initial conditions on molecular mixing in a low Atwood number(~7.5 x 10⁻⁴), high Schmidt number(~1000), RTI driven mixing layer is …

Development Of Virtual Cnc Machine Tools And Web-Based Machining Process Simulation: Mechanistic Cutting Force Models And Determination Of Specific Force Coefficients In Helical End Milling, Vinay Rao Talekar

Masters Theses

"This thesis presents the results of the investigations of mechanistic modeling and simulation of cutting forces in high speed end milling of titanium alloy, Ti-6Al-4V, and the determination of specific cutting and edge force coefficients for carbide bull-nose helical end-mill. A generalized mathematical model representing the outer geometry of an end-mill and the cutter edge geometry is presented. Mechanistic cutting force models have been developed for a general helical end-mill and modeled specifically for a bullnose helical end-mill. A MATLAB code for the mechanistic cutting force models have been developed for the simulation of cutting force components in end milling …

Selective Laser Sintering Of 13-93 Bioactive Glass, Krishna C. R. Kolan

Masters Theses

"Bioactive glasses are promising materials for bone scaffolds due to their ability to assist in tissue regeneration. When implanted in vivo, bioactive glasses can convert to hydroxyapatite, the main mineral constituent of human bone and form a strong bond with the surrounding tissues, thus providing an advantage over polymer scaffold materials. Bone scaffold fabrication using additive manufacturing techniques like selective laser sintering (SLS) provide control over pore interconnectivity during the fabrication of scaffold, which helps in mimicking human trabecular bone. 13-93 glass, a third-generation bioactive material designed to accelerate the body's natural ability to heal itself, was used in …

Design Of A Hydrogen Community For Santa Monica, Vijay Mohan

Masters Theses

"Hydrogen systems infrastructure development and fuel cell vehicles (FCVs) have the potential to replace the gasoline internal combustion engine vehicles thus increasing energy security and reducing greenhouse gas emissions. Hydrogen fueling infrastructure development is critical for the commercialization and consumer acceptability of the FCVs, thus recognizing hydrogen as an affordable transportation fuel. This paper presents the conceptual design of a scalable and reproducible hydrogen fueling station in Santa Monica, California. The various hydrogen production technologies have been evaluated and the usage of renewable energy sources such as biogas and landfill gas has been emphasized. The technical specifications of the hydrogen …

Experimental Investigation Of Cutting Forces, Temperature And Surface Roughness In End-Milling Of Hastelloy C-2000, Ryan Matthews

Masters Theses

"This thesis presents the results of experimental investigation of the effects of cutting parameters (spindle speed, feed per tooth, axial depth of cut and radial depth of cut) on the three components of cutting forces (F_x, F_y, F_z), workpiece temperature and surface roughness in end-milling of Hastelloy C-2000 alloy using design of experiments (DOE) and response surface methodology (RSM). End-milling experiments were conducted using 0.5 inch diameter end-mill on Cincinnati Milacron Sabre 750 vertical machining center using water based flood coolant. An inscribed central composite design of experiment was used to study the four …

Development Of Virtual Engineering Simulation For Lean Education, Akalpit Kiran Gadre

Masters Theses

"Global competition and customer demands are pressing modern industry operations to become leaner. The race among the global corporations to "go lean" demands engineers with an in-depth understanding of lean philosophies. An overview of current methods for teaching lean shows that they include small scale hands-on projects, presentations, and guest lectures. There is a need to incorporate a more immersive virtual simulation to further inspire students. Many lean simulation games are available in the market; however, they lack simplicity, ability to store the results, and modeling power.

The goal of this research is to develop a virtual simulation platform, enabling …

Evaluation Of Skin-Core Adhesion Bond And Low-Velocity Impact Behavior Of Honeycomb Sandwich Structures, Ramanjaneya R. Butukuri

Masters Theses

"Composite sandwich structures offer several advantages over conventional structural materials such as lightweight, high bending and torsional stiffness, superior thermal insulation and excellent acoustic damping. Some of the failure mechanisms in a composite sandwich structure are de-bonding of the composite facesheets from the core structure and damage due to low-velocity impact. In the first part of this work, adhesive fillet formation and adhesive mechanical strength are evaluated as a function of several different sandwich construction design variables. The effect of film adhesive thickness is studied. A process for reticulation of the adhesive is applied and studied. Optimized combinations of core …

Bi-Harmonic Atomic Force Microscopy, Santosh R. Kodandarama

Masters Theses

"In tapping mode atomic force microscopy, surface features are measured indirectly via the amplitude of the tapping cantilever. A change in surface profile is detectable only if it results in an amplitude change that is significant enough to be measured by the optics. Previous works have focused on improving sensitivity through the system's Q-factor, either by changing physical cantilever properties or using feedback control, but those approaches undesirably slow down the dynamic response. In this work we take a novel approach to sensitivity amplification by reshaping the tapping trajectory. By shaping the trajectory so that the probe spends a greater …

Development Of Hybrid Composite Bipolar Plates For Proton Exchange Membrane Fuel Cells, Nathaniel James Richie

Masters Theses

"Bipolar plates are one of the most expensive components of a PEM fuel cell and by far the heaviest. Bipolar plates are responsible for providing flow fields for reaction gases, acting as current collectors for electrons liberated during the chemical reaction inside the cell, and providing structural support for the fuel cell stack. Current PEM fuel cell bipolar plate technology is built on the use of sintered graphite which is costly and requires time-consuming machining. Furthermore, due to the brittle nature of graphite, plates must be made relatively thick which adds significant weight and volume to larger stacks, such as …

Design And Control Of A Multi-Axis Micro-Electro-Mechanical System Array For Coordinated Micro-Manipulation, Patrick Jesse White

Masters Theses

"Micro-electro-mechanical system design and implementation is a field that has received much attention over the past few decades. These robotic systems with features on the micro-scale have an unparalleled opportunity to change the way scientists interact with and understand micro and nano-scale phenomenon. Their capabilities allow experimentation that cannot be achieved with standard macro-scale equipment. Potential applications range from observing biological processes in living cells, to smart materials that automatically detect microcracks. So far, however, only a few truly successful applications have been realized. One of the most elusive goals in MEMS design is creating a system capable of coordinated …

Femtosecond And Nanosecond Laser Fabricated Substrate For Surface-Enhanced Raman Scattering, Adam Hamdorf

Masters Theses

"Surface-enhanced Raman scattering has many applications to chemical science, and shows great promise in the medical field because of its ability to provide "molecular fingerprinting" of probe molecules, whereby a material can be identified and potentially quantified. This is done by enhancing the normally weak Raman spectrum by many orders of magnitude with the use of fabricated substrates. It is therefore desirable to produce repeatable substrates with high enhancement factors for identification and quantification of samples. This thesis introduces a new method for generating such a substrate. By using femtosecond laser machining, gold sputtering, and nanosecond laser annealing, gold nanoparticles …

Risk Assessment For Conceptual Design Of Hydrokinetic Turbines, Praveen Kailkere Srinivas

Masters Theses

"Hydrokinetic energy is a relatively new concept in the field of renewable energy. The rotor of the turbine, immersed in water, uses the velocity from the flowing water to generate power. Thus the hydrokinetic turbines are also known as zero head turbines. These turbines can be installed in rivers, oceans and sea beds. The design of these systems depends on the site conditions, installation and maintenance costs. Since this technology has not been assessed for its potential power producing capabilities, not much research has been done in order to harness this form of renewable energy and to study the impact …

Innovative Air Breathing Design And Output Control For Portable Proton Exchange Membrane Fuel Cell, Amar Bala Sridhar

Masters Theses

"Proton Exchange Membrane (PEM) Fuel Cell Technology is an energy source that can provide several times more energy per unit volume than current lithium ion batteries that are available in the market today. The barriers that exist that prevent the fuel cell from entering the world of portable applications are mainly system architecture integration. The idea is to have a fully functioning fuel cell with optimum power output using an innovative chimney design. Tests were conducted to quantify the advantage of using a chimney with the fuel cell. Further research was done to shed light on how different chimney designs …

Impact Of Combustion Phasing On Energy And Availability Distributions Of An Internal Combustion Engine, Shawn Nicholas Wildhaber

Masters Theses

"High fuel efficiency has become an extremely desirable trait for internal combustion engines. This motivation has driven extensive research on methods to improve fuel efficiency on engines of various sizes. Many of these methods involve changes to the properties of the combustion process. One way to induce these property changes is through varying the phasing of combustion. Combustion phasing can be defined as the time in the engine cycle, specifically the compression and expansion strokes, where combustion occurs. A change in combustion phasing causes a change in combustion duration. The duration of combustion impacts how the energy and work potential …

Numerical Comparison Of Thermal And Kinetic Modification Of Hydrogen And Oxygen, John Benjamin Gaither

Masters Theses

"This document describes a new modeling technique used to compare thermal and kinetic modification of hydrogen and oxygen gas. The thermal model uses an equilibrium thermodynamic analysis to determine the heat required for given mole fractions of molecular and dissociated products. A kinetic model is developed for a mono-energetic electron beam and a Maxwellian energy distribution. The kinetic model uses electron impact cross sections for excitation, dissociation, and ionization tabulated from available source data between 0-1000 eV. Cross sections are used to calculate forward reaction rates, electron penetration depths, and associated product concentrations for excited, dissociated, and ionized species. The …

Analysis And Modeling Of Depth-Of-Cut During End Milling Of Deposited Material, Haythem Gaja

Masters Theses

"This study addresses depth-of-cut detection and tool-workpiece engagement using an acoustic emission monitoring system during milling machining for a deposited material. Online detection of depth-of-cut presents many technical difficulties. Researchers have used various types of sensors and methods to assess the depth-of-cut and surface errors. Due to the strong correlation between acoustic emission and cutting depth during the depth end milling process, it is useful to forecast the depth-of-cut from the acoustic emission signal. This work used regression analysis to model and detect the depth-of-cut. The experiments were carried out on a Fadal vertical 5-Axis computer numerical control machine using …

3-Dimensional Computational Fluid Dynamics Modeling Of Solid Oxide Fuel Cell Using Different Fuels, Sachin Laxman Puthran

Masters Theses

"Solid oxide fuel cell (SOFC) technology has been of great interest over many years due to its flexibility in using different fuels for operation; including the fundamental fuel i.e. Hydrogen. Various computational and numerical models have been developed along with experimental work to evaluate the performance as well as to identify and overcome the problems faced in the development of SOFC's. In an attempt to achieve efficient operation with respect to design and combined thermal and electrochemical perspective, the main objective of the proposed study is to present a three-dimensional computational model, which will serve as a framework for the …

Design And Development Of Manufacturing Methods For Manufacturing Of Pem Fuel Cell Mea's, Nikhil Pramod Kulkarni

Masters Theses

"This thesis focuses on design and manufacturing of Fuel cell components using Additive Manufacturing techniques and then in the later part on design and manufacturing of Membrane Electrode Assembly (MEA) which is a very important component in fuel cells. Additive manufacturing methods are fast and efficient manufacturing methods which are additive building up components layer by layer instead of conventional subtractive manufacturing techniques. This ensures low cost and faster manufacturing. Additive manufacturing is important for fuel cell component manufacturing since it is important in fuel cells to minimize wastage and reduce the cost. MEA is the basis of the cost …

Processing And Mechanical Characterization Of Polyurea Aerogels, Jared M. Loebs

Masters Theses

"The use of aerogels historically has been limited to extreme cases largely in part to the nature of their mechanical properties. Until recently many aerogels produced have been brittle and weak, though looking at their specific strength would suggest otherwise. This thesis outlines the processing and major mechanical properties of a relatively new type of aerogel, polyurea aerogel, that shows promise in a variety of fields including structures.

Processing polyurea aerogel begins with a liquid solution that solidifies to form a solid gel filled with liquid that is later removed by supercritical drying. Once dry, polyurea aerogels are difficult to …

Approximate Dynamic Programming Solutions With A Single Network Adaptive Critic For A Class Of Nonlinear Systems, Jie Ding

Doctoral Dissertations

"Approximate dynamic programming formulation implemented with an Adaptive Critic (AC) based neural network (NN) structure has evolved as a powerful technique for solving the Hamilton-Jacobi-Bellman (HJB) equations. As interest in ADP and the AC solutions are escalating with time, there is a dire need to consider possible enabling factors for their implementations. A typical AC structure consists of two interacting NNs which is computationally expensive. In this work, a new architecture, called the "Cost Function Based Single Network Adaptive Critic (J-SNAC)" is presented that eliminates one of the networks in a typical AC structure. This approach is applicable to a …

A Neural Network Based Approach For Path Planning On Costmap, Songjie Chen

Masters Theses

"In this thesis, a path planning method using a three-level hierarchical system model is proposed. In the top level of the hierarchy, the given location points to visit are taken as waypoints. The waypoint navigation process is formulated as a traveling salesman problem (TSP). The Lin-Kernighan algorithm is used to solve the TSP and transfer the solution to the lower level of the hierarchy. In the middle level, the path is represented by a grid-based costmap. A novel modified Grossberg neural network is designed to solve the point-to-point path planning. The bottom level of the hierarchy smoothens the path with …

Advanced Composites Using Non-Autoclave Processes: Manufacturing And Characterization, V. G. K. Menta

Doctoral Dissertations

"The objective of the present study is to develop non-autoclave processes to manufacture high performance composites for aerospace applications. In Paper 1, vacuum assisted resin transfer molding (VARTM) process was developed for elevated temperature composites. Use of VARTM process for fabricating high temperature resins presents unique challenges such as high porosity and low fiber volume contents. Two different vacuum bagging methods: Seeman Composite Resin Infusion Molding Process (SCRIMP) and Double Vacuum Bagging Infusion (DVBI) process were evaluated. Flow simulation tool was used to predict key flow parameters needed for the successful infusion. In Paper 2, honeycomb sandwich panels were manufactured …

Femtosecond Laser Micromachining Of Microstructures For Sensing And Detection, Yukun Han

Doctoral Dissertations

"This thesis focuses on the fabrication and analysis of miniature functional devices that can be used for different sensing and detection applications. As the first step, the surface characteristics and morphology of the micro/nano structures on substrates (fused silica and silicon) fabricated in water and in air by femtosecond laser were investigated. Based on this study, three micro devices have been designed and fabricated by femtosecond laser, and they were analyzed for optical and chemical sensing and detections. The three micro devices are: 1) an optical Fabry-Perot interferometer in optical fiber (made from fused silica) with smooth cavity surfaces. The …

Nonlinear Modeling And Simulation Of Radial Forging Process, Jian Chen

Doctoral Dissertations

"Radial forging is an important manufacturing process to produce large cannon barrels. It is used to improve the material properties and reduce the porosity of the billet. The objective of this study is to develop finite element models to investigate the behavior of the workpiece and predict the elimination of void defects in the radial forging process. A nonlinear coupled finite element model has been developed to study the behavior of a large-diameter tube subjected to mechanical and thermal loadings in hot radial forging. The model is formulated in a three-dimensional frame, accounting for both axial and circumferential effects. A …