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Articles 1  16 of 16
FullText Articles in Engineering Science and Materials
Experimental Validation For The Theory Of Blisters’ Instabilities, Hongtian Zhu
Experimental Validation For The Theory Of Blisters’ Instabilities, Hongtian Zhu
Mechanical Engineering Graduate Theses & Dissertations
Blister formation is a universal problem that can be witnessed within a wide range of contents. It is first documented as a side effect of syringomyelia and other diseases. Later on, the forming of blisters are also observed during the cell apoptosis, which leads to the hypothesis that it could have some intricate relationships with the death of living organisms. Other than biological problems, blister forming is also a common phenomenon in thin film technologies. Therefore, the research in the forming of blisters is essential and critical in both engineering and science fields.
In this thesis, we study the problem ...
Lamb Waves With Conical Dispersion At Zero Wavenumber, David M. Stobbe
Lamb Waves With Conical Dispersion At Zero Wavenumber, David M. Stobbe
Mechanical Engineering Graduate Theses & Dissertations
Lamb waves are guided elastic waves in plates. These waves are dispersive, with the frequency and wavenumber related by the wellknown RayleighLamb equation. Generally, at zero wavenumber the dispersion curves are parabolic and the waves are nonpropagating thickness resonances. For distinct values of Poisson’s ratio, however, degeneracy can occur between thickness resonance modes. At these coincidence frequencies the dispersion curves become linear and in a threedimensional representation the dispersion surface is shaped like a cone. This behavior is referred to as conical dispersion. Waves excited at coincidence frequencies maintain the infinite phase velocity associated with thickness resonances but transport ...
Investigating The Physical Mechanisms That Impact Electric Fields In The Atmosphere, Greg M. Lucas
Investigating The Physical Mechanisms That Impact Electric Fields In The Atmosphere, Greg M. Lucas
Aerospace Engineering Sciences Graduate Theses & Dissertations
The underlying physics and dynamics of the atmosphere drive electric currents and establish electric fields in a phenomenon known as the global electric circuit (GEC). The GEC has been observed and modeled with limiting assumptions and parameterizations in previous research. This thesis describes the incorporation of a physicsbased GEC modeling scheme into a sophisticated climate model to describe the evolution of GEC currents, groundionosphere potential, electric fields, and conductivity within the atmosphere. Supporting measurements of atmospheric electric fields over time were used to describe the impact of local meteorological changes and assess the GEC contribution to nearsurface electric fields.
The ...
Hierarchical Multiscale Modeling To Inform Continuum Constitutive Models Of Soils, Erik Wallace Jensen
Hierarchical Multiscale Modeling To Inform Continuum Constitutive Models Of Soils, Erik Wallace Jensen
Civil Engineering Graduate Theses & Dissertations
The behavior of soils is fundamentally the combined interactions between billions and billions of individual particles and particle matrices. For computational tractability and despite this fact, many soil models assume the material is a continuum essentially averaging the interparticle interactions to predict the behavior of the bulk material. In recent years, multiscale modeling techniques have been developed to reintroduce the effect of the grainscale interactions to help model situations where the continuum assumption fails, such as shear band development in triaxial tests or soil disaggregation under blast loading. One of such multiscale models called hierarchical upscaling, or globallocal analysis, model ...
Finite Strain Micromorphic Elasticity, Elastoplasticity, And Dynamics For Multiscale Finite Element Analysis, Farhad Shahabi
Finite Strain Micromorphic Elasticity, Elastoplasticity, And Dynamics For Multiscale Finite Element Analysis, Farhad Shahabi
Civil Engineering Graduate Theses & Dissertations
This study stands as an attempt to consider the microstructure of materials in a continuum framework by the aid of micromorphic continuum theory in the sense of Eringen. Since classical continuum mechanics do not account for the microstructural characteristics of materials, they cannot be used to address the macroscopic mechanical response of all microstructured materials. In the “representative volume element (RVE)” based methods, classical continuum mechanics may be applied to analyze mechanical deformation and stresses of materials at the relevant microstructural lengthscale (such as grains of a polycrystalline metal, or sand, or metal matrix composite, etc), but when applying standard ...
Nonlinear Dispersive Elastic Waves In Solids: Exact, Approximate, And Numerical Solutions, Romik Khajehtourian
Nonlinear Dispersive Elastic Waves In Solids: Exact, Approximate, And Numerical Solutions, Romik Khajehtourian
Aerospace Engineering Sciences Graduate Theses & Dissertations
Wave motion lies at the heart of many disciplines in the physical sciences and engineering. For example, problems and applications involving light, sound, heat, or fluid flow are all likely to involve wave dynamics at some level. A particular class of problems is concerned with the propagation of elastic waves in a solid medium, such as a fiberreinforced composite material responding to vibratory excitations, or soil and rock admitting seismic waves moments after the onset of an earthquake, or phonon transport in a semiconducting crystal like silicon. Regardless of the type of wave, the dispersion relation provides a fundamental characterization ...
Autonomous Mission Design In Extreme Orbit Environments, David Allen Surovik
Autonomous Mission Design In Extreme Orbit Environments, David Allen Surovik
Aerospace Engineering Sciences Graduate Theses & Dissertations
An algorithm for autonomous online mission design at asteroids, comets, and small moons is developed to meet the novel challenges of their complex nonKeplerian orbit environments, which render traditional methods inapplicable. The core concept of abstract reachability analysis, in which a set of impulsive maneuvering options is mapped onto a space of highlevel mission outcomes, is applied to enable goaloriented decisionmaking with robustness to uncertainty. These nuanced analyses are efficiently computed by utilizing a heuristicbased adaptive sampling scheme that either maximizes an objective function for autonomous planning or resolves details of interest for preliminary analysis and general study. Illustrative examples ...
RollToRoll Atomic Layer Deposition Of Ultrabarriers, Alexander Yersak
RollToRoll Atomic Layer Deposition Of Ultrabarriers, Alexander Yersak
Mechanical Engineering Graduate Theses & Dissertations
Atomic layer deposition (ALD) is a bottomup, gas phase, thin film deposition technique based on sequential, selflimiting binary surface reactions. The precise subnanometer film thickness control and conformal nature of this process have led to various commercial applications of ALD. However, ALD films are most commonly deposited in batch processes at low pressures, which raises throughput and/or cost concerns for many otherwise promising applications. This problem can be solved by spatial ALD (SALD) which is a version of the ALD technique where the precursors are separated in space rather than time. We have demonstrated the first atmospheric pressure rolltoroll ...
The Particle Based Moving Interface Method For Soft Matter Mechanics And Fluid/Membrane Interactions With Applications To Biological Cells, Louis Cyrille Foucard
The Particle Based Moving Interface Method For Soft Matter Mechanics And Fluid/Membrane Interactions With Applications To Biological Cells, Louis Cyrille Foucard
Civil Engineering Graduate Theses & Dissertations
The mechanics of the interaction between a fluid and a soft interface (such as an elastic membrane or shell) undergoing large deformations appears in many places, such as in biological systems or industrial processes. We present here an Eulerian approach that describes the mechanics of an interface and its interactions with a surrounding fluid via the socalled Navier boundary condition. The interface is modeled as a curvilinear surface with arbitrary mechanical properties across which discontinuities in pressure and tangential fluid velocity can naturally be enforced using a modified version of the extended finite element method. The tracking and evolution of ...
Fish Skin: A Thin, Flexible, Protective Membrane, Natasha Elaine Funk
Fish Skin: A Thin, Flexible, Protective Membrane, Natasha Elaine Funk
Civil Engineering Graduate Theses & Dissertations
Although there have been recent efforts to characterize the important structural characteristics of fish scales and fish skin (e.g., the tensile strength [9], puncture strength [19], bending rigidity [10]), attempts to fabricate materials that mimic natural fish skins have remained limited. This thesis presents a synthetic fish skin material designed to replicate the structural, dimensional, mechanical, and functional aspects of natural teleost fish skin comprised of leptoidlike scales. The material design and fabrication has been simplified to include (i) a low modulus elastic mesh or dermis layer that holds (ii) relatively (in comparison to the mesh) rigid, plastic scales ...
Confined Masonry: Theoretical Fundamentals, Experimental Test, Finite Element Models, And Future Uses, Lan T. Nguyen
Confined Masonry: Theoretical Fundamentals, Experimental Test, Finite Element Models, And Future Uses, Lan T. Nguyen
Civil Engineering Graduate Theses & Dissertations
Inspired from the MS thesis that investigated the underlying relationship between the implicit level of risk accepted for natural hazards and the level of economic, social and political development of Haiti, a developing country, this dissertation focuses structurally on the use of lowrise confined masonry (CM) buildings in natural hazard consideration areas. The research emphasizes the responses of the CM shear wall structure as a whole, as well as the material conditions in detail. Key findings are presented from experimental tests, computational modeling procedures, analytical results, and reliability analysis for CM structures followed with the summary of the behavior of ...
The Effect Of Temperature On Moisture Transfer In Concrete, Yao Wang
The Effect Of Temperature On Moisture Transfer In Concrete, Yao Wang
Civil Engineering Graduate Theses & Dissertations
Moisture transfer is a major concern for predicting the durability and serviceability of concrete. To predict moisture transfer in concrete, one should not only analyze the effect of moisture gradient, but also consider the effect of temperature gradient. This effect is called Soret effect. Moreover, depending on the experimental results, the value of coefficient was calculated and used to quantify the Soret effect.
This thesis presents results of an experimental investigation of how the temperature gradient affects the moisture in concrete. The thesis includes two major parts. The first part introduces the background information as well as the theoretical review ...
Thermal Strain Of Concrete Under Low Temperatures And Durability And Processing Techniques Of Concrete With Cnts, Xingang Wang
Thermal Strain Of Concrete Under Low Temperatures And Durability And Processing Techniques Of Concrete With Cnts, Xingang Wang
Civil Engineering Graduate Theses & Dissertations
This thesis consists of two topics: Thermal strain of concrete under low temperatures, and durability and processing techniques of concrete with CNTs. The low temperature test studies the antifreezing action of concrete under cooling environment. Concrete mixes using different amounts of airentraining agent and water/cement ratios were made and cured under different humidity environments. During the cooling process from 10 ºC to 25 ºC, the strain of concrete was measured every 3~5 ºC. The straintemperature curve of concrete under different mixing proportion was produced from these results. A numerical model was developed based on the theory of the ...
Model Development And Experimental Validation Of Pressure Independent Hydronic Circuits, Justin Thomas Bellucci
Model Development And Experimental Validation Of Pressure Independent Hydronic Circuits, Justin Thomas Bellucci
Civil Engineering Graduate Theses & Dissertations
Computer modeling is quickly becoming a more accessible method to evaluate the performance of complex building systems, due in part to the recent advance in computing power over the last decade. Rising energy costs, stricter building codes, the threat of global climate change and governmental pressure have all influenced building owners, architects, engineers and system operators to design and operate the world's building stock in a more energy efficient manner. Particularly important in large buildings and campuses are the hydronic flow networks that deliver chilled water to the cooling coils in air handling units for the purpose of regulating ...
The Influence Of Representative Volume Element Size, Soil Fabric, And Interparticle ElastoPlasticity In ThreeDimensional Ellipsoidal Discrete Element Modeling Of Granular Assemblies, Yevgeniy Kaufman
Civil Engineering Graduate Theses & Dissertations
In this comparative study of RVEs, a DEM code ELLIP3D is utilized to simulate quartz sand in triaxial compression tests with particle assemblies attained from an in situ fabric generated by synchrotron Xray microcomputed tomography. In order to attain meaningful results for engineered systems at the macroscopic scale using DEM, RVE volume sizes play a significant role in the accuracy of simulating physical experiments. Simulation time or the number of particles limits the capacity of DEM to simulate largescale granular systems, which is why it is crucial to determine an efficient quantity and quality of RVEs.
ELLIP3D simulations have been ...
Thermomechanics Of Shape Memory Polymers And Composites, Qi Ge
Thermomechanics Of Shape Memory Polymers And Composites, Qi Ge
Mechanical Engineering Graduate Theses & Dissertations
This dissertation presents studies with a combination of experiment, theory, and simulation on a broad range of polymeric material systems (both established and emerging), that exhibit the shape memory (SM) effect. The goals of the studies are to understand complex thermomechanical behaviors of shape memory polymers (SMPs), develop constitutive models to describe the behaviors and use the developed models to advance the development and deployment of SMPs. The general approach used in the studies is independent of the material system and consists of: i) sample fabrication and thermomechanical experiments including dynamic mechanical analysis (DMA), stressstrain behaviors and thermal strain tests ...