Mechanical Engineering Commons^™

Design Optimization Of Geometrical Parameters And Material Properties Of Vibrating Bimorph Cantilever Beams With Solid And Honeycomb Substrates For Maximum Energy Harvested, Jasmin Adeshara

All Theses

The objective of this thesis is to maximize the energy harvested from a vibrating bimorph cantilever beam by optimizing the geometrical parameters and the material properties of the piezoelectric beam. A three-dimensional finite element (FEA) model is developed to design a vibrating bimorph cantilever beam for energy harvesting. The reference piezoelectric material used in the design is Lead Zirconate Titanate (PZT-5H) and the substrate sandwiched between the two piezoelectric plates is brass. Three types of models are analyzed and compared in this work by modifying the brass substrate geometry- a solid homogenous substrate, a regular honeycomb substrate and an auxetic …

Moving Domain Computational Fluid Dynamics To Interface With An Embryonic Model Of Cardiac Morphogenesis, Juhyun Lee, Mahdi Esmaily Moghadam, Ethan Kung, Hung Cao, Tyler Beebe, Yury Miller, Beth L. Roman, Ching-Ling Lien, Neil C. Chi, Alison L. Marsden, Tzung K. Hsiai

Publications

Peristaltic contraction of the embryonic heart tube produces time- and spatial-varying wall shear stress (WSS) and pressure gradients (∇P) across the atrioventricular (AV) canal. Zebrafish (Danio rerio) are a genetically tractable system to investigate cardiac morphogenesis. The use of Tg(fli1a:EGFP)y1 transgenic embryos allowed for delineation and two-dimensional reconstruction of the endocardium. This time-varying wall motion was then prescribed in a two-dimensional moving domain computational fluid dynamics (CFD) model, providing new insights into spatial and temporal variations in WSS and ∇P during cardiac development. The CFD simulations were validated with particle image …

Nonlinear Dynamics Of Carbon Nanotubes Under Soft Alternating Current Actuation, Le Luo

Theses and Dissertations - UTB/UTPA

This thesis work deals with electrostatically actuated Carbon Nanotubes (CNTs) cantilevers. Four forces are acting on the CNTs cantilever, namely damping, elastic, electrostatic and van der Waals forces. The van der Waals force is significant for values of 50 nm or lower of the gap between the CNTs and the ground substrate. As both electrostatic and van der Waals forces are nonlinear, and the CNTs electrostatic actuation is given by alternating current (AC) voltage, the CNTs undergo nonlinear parametric dynamics. The Method of Multiple Scales (MMS) and Reduced Order Model (ROM) are employed to investigate the system under soft excitation …

Aspen Plus Simulation Of Biomass Gasification In A Steam Blown Dual Fluidised Bed, Wayne Doherty, Anthony Reynolds, David Kennedy

Book/Book Chapters

The efficient utilisation of biomass resources is of utmost importance. Biomass gasification offers much higher efficiencies than combustion. Gasification is a process in which a fuel is converted to a combustible gas (syngas). A dual fluidised bed gasifier known as the fast internally circulating fluidised bed (FICFB) was selected. It has been demonstrated at industrial scale and data is readily available for model validation. An Aspen Plus model was developed to simulate the FICFB gasifier. The model is based on Gibbs free energy minimisation and the restricted equilibrium method was used to calibrate it. The model has been validated and …

Design And Optimization Of A Railroad Conductive Suspension Element Pad Composed Of Thermoplastic Polyurethane And Carbon Black, Ruben Suarez Jr.

Theses and Dissertations - UTB/UTPA

The AdapterPlus™ Pad, made from thermoplastic polyurethane (TPU), is used to enhance steering and prevent metal-to-metal contact between the railcar side frame and the bearing adapter. Although the AdapterPlus™ Pad acts as a pedestal liner in the suspension assembly, it must allow electric current to flow from the rail, through the bearing adapter wall to the side frame in order to activate a solenoid air valve that releases cargo gates. Currently, the pad uses copper inserts that allow current through. Because the Adapter Plus™ Pad is subject to large dynamic loads, the copper inserts permanently deform losing contact and cutting …

Topology Optimization Using A Level Set Penalization With Constrained Topology Features, Luis Fernandez

All Theses

Topology optimization techniques have been applied to structural design problems in order to determine the best material distribution in a given domain. The topology optimization problem is ill-posed because optimal designs tend to have infinite number of holes. In order to regularize this problem, a geometrical constraint, for instance the perimeter of the design (i.e., the measure of the boundary of the solid region, length in 2D problems or the surface area in 3D problems) is usually imposed. In this thesis, a novel methodology to solve the topology optimization problem with a constraint on the number of holes is proposed. …

Computational Representation Of Linguistic Semantics For Requirement Analysis In Engineering Design, Alex Lash

All Theses

The objective of this research is to use computational linguistics to identify semantic implicit relationships between text-based relationships. Specifically, natural language processing is used to implement linguistic semantics in requirement analyzers. Linguistic semantics is defined as the meaning of words beyond their string form, part of speech, and syntactic function. Many existing design tools use part of speech tagging and sentence parsing as the foundation of their requirement analysis but ultimately use string algorithms to evaluate requirements. These string algorithms cannot capture the implicit knowledge in requirements. This research compares five methods of requirement analysis. A manual analysis provides the …

Robust Motion Estimation With Rgb-D Cameras, Robert C. Leishman, Daniel Koch, Timothy W. Mclain

Faculty Publications

Estimating vehicle motion using vision sensors in real time has been greatly explored in the past few years due to speed improvements and advances in computer hardware. Six degree of freedom motion estimation using vision information is desirable due to a vision sensors low cost, low power requirements and light weight and for the quality of the solutions that can be obtained using few assumptions about the environment. However, cameras have the downside of not providing good estimates when visual features are sparse or not available. Also, there are problems with changes in lighting and when light is low or …

Interface Properties Of Bio-Based Composites Of Polylactic Acid And Bamboo Fibers, Quentin Viel

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Environmental impact plays an ever-increasing role in the industrial production of materials, and because of its importance, the scientific community is examining a wide variety of new materials that are more environmentally friendly. Bioplastics are characterized by the fact that the usual petrochemical resins (polypropylene, polyethylene etc.) are replaced by bio-sourced resins and the reinforcements (glass fibers, carbon fibers etc.) are replaced by natural fibers (bamboo, flax, cotton, etc.). Polylactic acid (PLA) is a biodegradable polymer that is increasingly used in biomedical applications and in packaging. Additionally, bamboo is a promising source of fibers that could be used as reinforcement. …

Developing And Characterizing A Rapid Prototyping Stereo-Lithography Machine To Produce Interpenetrating Polymer Network Systems, Lena R. Butterfield

Department of Mechanical and Materials Engineering: Dissertations, Theses, and Student Research

Rapid prototyping and interpenetrating network systems (IPNs) ideas and technologies were studied in order to develop a rapid prototyping machine capable of producing IPNs. This work was done as collaboration between the University of Nebraska-Lincoln and the University of Rouen, France, and is part of a project of controlling material property distribution by means of gradient IPN production within a rapid prototyping machine.

A standard stereo-lithography rapid prototyping (RP) machine was built and then modified for the purpose of producing an IPN system composed of an acrylic component, bisphenol A propoxylate diacrylate (BPA-PDA) and an epoxy component, 3,4 epoxycyclohexyl-methyl 3,4 …

Ideal Optimum Performance Of Propellers, Lifting Rotors And Wind Turbines, Ramin Modarres

All Theses and Dissertations (ETDs)

No abstract provided.

Stochastic Reconstruction Of Multiple Source Atmospheric Contaminant Dispersion Events, Derek Wade, Inanc Senocak

Mechanical and Biomedical Engineering Faculty Publications and Presentations

Reconstruction of intentional or accidental release of contaminants into the atmosphere using concentration measurements from a sensor network constitutes an inverse problem. An added complexity arises when the contaminant is released from multiple sources. Determining the correct number of sources is critical because an incorrect estimation could mislead and delay response efforts. We present a Bayesian inference method coupled with a composite ranking system to reconstruct multiple source contaminant release events. Our approach uses a multi-source data-driven Gaussian plume model as the forward model to predict the concentrations at sensor locations. Bayesian inference with Markov chain Monte Carlo (MCMC) sampling …

Experimental And Analytical Investigation Of The Transient Thermal Response Of Air Cooled Data Centers, Hamza Salih Erden

Dissertations - ALL

This work investigates the transient response of the thermal environment in air cooled data centers through experiments, analytical and computational tools. The key thermal characteristics of the various data center components were extracted from a set of experiments. This includes the development of practical experimental procedures for the thermal characterization of servers solely based on air temperature measurements and the transient response of the computer room air handlers. The knowledge of thermal characteristics paves the way for the physics-based lumped-capacitance models. A CFD-based transient simulation of the air temperature field, in which the transient thermal response of the servers was …

A Simplified Approach To Thermomechanical Fatigue And Application To V-Shaped Notches, Thomas Bouchenot

HIM 1990-2015

A vast array of high value parts in land- and air-based turbomachinery are subjected to non-isothermal cycling in the presence of mechanical loading. Crack initiation, growth and eventual failure more significantly reduce life in these components compared to isothermal conditions. More accurate simulation of the stress and strain evolution at critical locations of components, as well as test specimens, can lead to a more accurate prediction of remaining life to a structural integrity specialists. The focus of this thesis is to characterize the effects of thermomechanical fatigue (TMF) on generic turbomachinery alloy. An expression that can be used to estimate …

Microscopic Surface Textures Created By Interfacial Flow Instabilities, Jing Gu

HIM 1990-2015

In nature, microscopic surface textures impact useful function, such as the drag reduction of shark skin (Dean & Bhushan, 2010) and superhydrophobicity of the lotus leaf(Pan, Kota, Mabry, & Tuteja, 2013). In this study, we explore these phenomena by re-creating microscopic surface textures via the method of interfacial flow instability in drying polyvinylidene fluoride (PVDF) acetone solutions. In general, PVDF films can be made using either spin coating or electrospray deposition with various weight concentrations in acetone. In order to study the morphology of the porous structure of PVDF films, wet deposition samples were fabricated by spin coating or near-field …

Optimization Problem Formulation For Predicting Knee Muscle And Contact Forces During Gait, Gil Serrancolí, Jonathan P. Walter, Allison Kinney, Benjamin J. Fregly, Josep M. Font-Llagunes

Mechanical and Aerospace Engineering Faculty Publications

The human body has more muscles than degrees of freedom (DOF), which leads to indeterminacy in the muscle force calculation. In this study, an optimization problem to estimate the lower-limb muscle forces during a gait cycle of a patient wearing an instrumented knee prosthesis is formulated. It consists of simulating muscle excitations in a physiological way while muscle parameters are calibrated.

Synergies Controls Improve Prediction Of Knee Contact Forces And Muscle Excitations During Gait, Benjamin J. Fregly, Jonathan P. Walter, Allison Kinney, Scott A. Banks, Darryl D. D'Lima, Thor F. Besier, David G. Lloyd

Mechanical and Aerospace Engineering Faculty Publications

This study investigates whether use of muscle excitation controls constructed from subjectspecific muscle synergy information can improve optimization prediction of knee contact forces and muscle excitations during walking. Muscle synergies quantify how a large number of experimental muscle electromyographic (EMG) signals can be reconstructed by linearly mixing a much smaller number of neural commands generated by the nervous system. Our hypothesis was that controlling all muscle excitations with a small set of experimentally calculated neural commands would improve prediction of knee contact forces and leg muscle excitations compared to using independently controlled muscle excitations.

Investigation Of Sound Transmission Through An Open Window Into A Room, Caleb F. Sieck

Durham School of Architectural Engineering and Construction: Dissertations, Theses, and Student Research

In recent decades, noise levels in cities and the associated annoyance and health consequences have become regular topics of discussion. As a result, the assessment of environmental noise transmitting into buildings has received much attention. Current models of sound transmission through open windows have either neglected their thickness or the presence of a room behind on one side. The objectives of the present work were to (1) develop an accurate analytical model of sound transmission through an open window of finite thickness into a room, (2) verify the analytical model using a finite element model and experimental measurements, and (3) …

Real-Time Visualization Of Finite Element Models Using Surrogate Modeling Methods, Ryan C. Heap

Theses and Dissertations

Finite element analysis (FEA) software is used to obtain linear and non-linear solutions to one, two, and three-dimensional (3-D) geometric problems that will see a particular load and constraint case when put into service. Parametric FEA models are commonly used in iterative design processes in order to obtain an optimum model given a set of loads, constraints, objectives, and design parameters to vary. In some instances it is desirable for a designer to obtain some intuition about how changes in design parameters can affect the FEA solution of interest, before simply sending the model through the optimization loop. This could …

Water Desalination And Purification Using Renewable Energy Technologies, Michael Louis Broggi

Masters Theses and Doctoral Dissertations

Water is an essential element of life as well as an integral cornerstone of any civilizations economic development. Although taken for granted by most living in developed nations, access to clean drinking water still proves to be a daily struggle for more than 1.2 billion individuals around the globe. More than 10% of the global population consumes food grown using waste water on a daily basis. Desalination facilities are in operation around the globe but are extremely large consumers of energy. There are several options available today which can reduce this energy demand and bring the desalination process down to …

Development Of Stationary And Mobile Tailgating Detection Solutions For Ground Vehicles, Tyler Zellmer

All Theses

Improving the safety of North American roadways is a top priority for government agencies and transportation organizations alike. Regulations on appropriate driving behavior have been developed to minimize the likelihood of crashes occurring, but law enforcement tools remain to be fully developed and applied in the field. One prominent example of this is tailgating – the dangerous act of one ground vehicle following another too closely. This activity is responsible for thousands of crashes every year, but police officers currently have few tools to accurately detect and document tailgating events. Though tailgating often occurs in a wide variety of vehicle …

Non-Redundant Sensor Fault Detection Using An Improved Dynamic Model, Brandon Cannon, Robert C. Leishman, Timothy W. Mclain, Joseph Jackson, Jovan Boskovic

Faculty Publications

This paper proposes a method of detecting faults in non-redundant sensors. Such a method is advantageous for small unmanned aerial vehicles (UAVs), which are prevented from carrying redundant sensors due to size, weight, and power constraints. The method we propose uses a multiplicative extended Kalman lter (MEKF) for estimation and employs hypothesis testing to detect faults. This method has been shown to detect bias, drift, and increased noise in a non-redundant sensor real-time on board an autonomous rotorcraft.

Numerical Modeling Of Heat Pipe Radiator And Fin Size Optimization For Low And No Gravity Environments, Virginia Ruth Bieger

UNLV Theses, Dissertations, Professional Papers, and Capstones

A heat-pipe radiator element has been designed and modeled to study the efficiency of heat transfer for low and no gravity environments, like in lunar environments. The advantages of using heat pipe includes the significant weight reducing and heat transfer efficiency. The heat transfer can be enhanced by the use of condenser sections with attached fins.

A series of various geometries of solid fins and heat pipes with and without fins were modeled using FLUENT®. This was done to determine the validity of using a heat pipe in lieu of a solid fin projection. A heat pipe had a 25 …

3d Modeling And Design Optimization Of Rod Shaped Ionic Polymer Metal Composite Actuator, Siul A. Ruiz

UNLV Theses, Dissertations, Professional Papers, and Capstones

Ionic polymer-metal composites (IPMCs) are some of the most well-known electro-active polymers. This is due to their large deformation provided a relatively low voltage source. IPMCs have been acknowledged as a potential candidate for biomedical applications such as cardiac catheters and surgical probes; however, there is still no existing mass manufacturing of IPMCs. This study intends to provide a theoretical framework which could be used to design practical purpose IPMCs depending on the end users interest.

This study begins by investigating methodologies used to develop quantify the physical actuation of an IPMC in 3-dimensional space. This approach is taken in …

Particle Electrophoresis And Magnetophoresis In Microchannels, Litao Liang

All Theses

In current pharmaceutical and biotechnology industries with clinical applications, an increased demand for flow control and cell manipulation on the micrometer scale has emerged. Electrokinetic, magnetic and many other physics fields have been exploited to meet this demand. However, due to the requirement for sophisticated micro-structures and the interference of the increasing significance of many `trivial' physics properties (surface potential, permittivity, etc.) at the smaller scale, most applications encounter poor maneuverability and high operation/fabrication complexity issues. Very few attempts have been made to bypass these requirements while maintaining the same control and efficiency. This thesis research investigates the fundamental behaviors …

Finite Element Analysis Of Effective Mechanical Properties, Vibration And Acoustic Performance Of Auxetic Chiral Core Sandwich Structures, Hrishikesh Joshi

All Theses

Honeycomb cellular materials are widely used in engineering applications due to their high strength to weight ratio and controllable effective mechanical properties. The effective properties are controlled by varying the geometry of the repetitive unit cells of honeycomb structure. Sandwich panels made of honeycomb cores are beneficial in many applications including vibration isolation and sound transmission reduction. Sandwich panels with standard honeycomb core configurations have previously been studied with regards to sound transmission behavior. It has been established that the auxetic honeycomb cores, having negative in-plane Poisson's ratio, exhibit higher sound transmission loss as compared to regular honeycomb cores. In …

Novel Side-Vent-Channel Based Blast Mitigation Concept For Light Tactical Vehicles, Ramin Yavari

All Theses

A new concept solution for improving survivability of the light tactical military vehicles to blast-loads resulting from a shallow-buried mine detonated underneath such vehicles is proposed and critically assessed using computational engineering methods and tools. The solution is inspired by the principle of operation of the rocket-engine nozzles, in general and the so called 'pulse detonation' rocket engines, in particular, and is an extension of the recently introduced so-called 'blast chimney' concept (essentially a vertical channel connecting the bottom and the roof and passing through the cabin of a light tactical vehicle).
Relative to the blast-chimney concept, the new solution …

Lifting-Line Predictions For Induced Drag And Lift In Ground Effect, W. F. Phillips, Doug F. Hunsaker

Mechanical and Aerospace Engineering Faculty Publications

Closed-form relations are presented for estimating ratios of the induced-drag and lift coefficients acting on a wing in ground effect to those acting on the same wing outside the influence of ground effect. The closed-form relations for these ground-effect influence ratios were developed by correlating results obtained from numerical solutions to Prandtl’s lifting-line theory. Results show that these influence ratios are not unique functions of the ratio of wing height to wingspan, as is sometimes suggested in the literature. These ground-effect influence ratios also depend on the wing planform, aspect ratio, and lift coefficient.

Model Based Control Of Machining Processes: Exploration Of Bayesian Statistical Methods For Identification And Control, Parikshit Mehta

All Dissertations

Machining process modeling & simulation as well as in-process monitoring and control have been identified as key technological factors to power efficient manufacturing facilities of tomorrow. The effective utilization of process models and in-process control are aimed towards improving profitability of the manufacturing process. To that end, the objective of this research work is to improve machining performance by implementing in-process control using model based control strategies, while considering stochastic models of machining process. Towards satisfying that objective, three research questions are asked.
1) What are metrics of measuring machining performance and which machining process models are important to consider …

Jet Instability And Droplet Formation For Bio-Printing Applications, Leigh Herran

All Dissertations

The research conducted in this dissertation was done to obtain a fundamental understanding of the formation of droplets in a drop-on-demand (DOD) inkjetting setup when the ink contains a polymer additive. The objective is to precisely control and even predict the forming dynamics and final droplet characteristics (velocity, size and satellite elimination). A polymeric fluid called sodium alginate has been gaining attention due to its highly bio-compatible nature. Solutions of sodium alginate were used as the ink material and in some cases compared with an equivalent Newtonian fluid (same zero-shear viscosity). The droplets were inspected in one of two ways: …