Mechanical Engineering Commons^™

Material Characterization Of Nitinol Wires For The Design Of Actuation Systems, Sean P. Kennedy

Master's Theses

A series of tests were performed on nickel-titanium alloy wire, also known as nitinol, to determine the plausibility of designing an actuator using this wire as the method of actuation. These tests have been designed to fully characterize how the wire behaves under steady state and transient conditions allowing for a specific wire selection to be made given known actuator specifications which will result in an efficient design. The wire transient data can be used to design a controller which reduces the actuation time. The research done for the overall project covers a wide scope including wire hysteresis, nitinol transition …

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.

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 …

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 …

Development Of A Controllable Polymer System Using Interpenetrating Networks, Emilie Bobo

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

My research partners and I have studied the possibility of building a material system with controllable properties using two interpenetrating polymer networks (IPNs). This study is part of a project to build a rapid prototyping system that allows for the printing of objects with predefined spatial distribution of properties, with the goal that property distributions are controlled though interactions at the molecular level.

One can change the properties of an IPN by adjusting the ratio of interpenetrating networks present in a given cured mixture. This is similar to how one obtains different shades of the color green by gradually changing …

Design Of A Compliant Underactuated Robotic Finger With Coordinated Stiffness, Etienne Dessauw

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

The concept of underactuation has been previously developed in the robotic field for grasping applications. For these anthropomorphic grippers, the minimization of the number of input signals, or in other words underactuation, is the most expected characteristic. This method has become very popular in recent decades. Indeed, by minimizing the number of input signals, it minimizes the complexity of the system’s control and at the same time avoids increased weight and cost. The inconvenience of such a technique is that the design of this type of system remains a difficult task if the behavior of the underactuated set of joints …

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 …

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 …

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 …

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 …

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) …

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 …

Nutrient And Carbon-Dioxide Requirements For Large-Scale Microalgae Biofuel Production, Benjamin K. Shurtz

All Graduate Theses and Dissertations, Spring 1920 to Summer 2023

Ever-increasing fuel prices and a limited supply of oil worldwide are threatening our economy and way of life in both the near and distant future. In order to reduce oil
dependence, the US Department of Energy (DOE) has established a goal that by the year 2030, 30% of the US transportation fuel will be renewable. The goal equates to
approximately 60 billion gallons per year of renewable fuel.

In an effort to reach the DOE renewable fuel goal, numerous types of plants are being studied, whose oil can be harvested and refined to serve as replacement fuel.
Among the various …

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 …

Numerical Simulation Of Separated And Secondary Flows In Diffusing S-Ducts For Air Breathing Propulsion, Colin James Fiola

All Theses and Dissertations (ETDs)

No abstract provided.

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.