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Modeling Corrosion in Suspension Bridge Main CablesKaranci, Efe January 2017 (has links)
Accurately determining the current state of a suspension bridge’s main cables is a critical component to reliably assessing the safety of the bridge. The primary cause for the deterioration of cable strength with time is universally recognized to be the corrosion of high strength steel wires, which together comprise the main cable. Hidden from view by the cable wrapping, this corrosion often goes undetected for years and is typically only discovered during costly and intrusive inspections. Furthermore, current inspection methods provide an incomplete picture of the variation in wire condition across the cable cross section. As a result, cable strength estimation techniques that rely solely on inspection data introduce a considerable degree of uncertainty. Finally, a method has not been developed for estimating the continuing decline in cable strength due to ongoing corrosion. A recent direction in research attempts to address the shortcomings of current inspection methodologies and the intent of this thesis is to further build upon these findings.
In these recent studies, environmental conditions inside main cables are monitored to obtain information regarding the corrosive nature of the cable’s internal environment. The first goal of this thesis is to further this research direction by introducing a corrosion rate model for bridge wires that relates the monitored environmental parameters within a cable to the corrosion rate of bridge wires. Initially, temperature, relative humidity, pH, and Cl- concentration have been identified as the most relevant variables for predicting the corrosion rate of a bridge wire. By applying machine learning methods to a corrosion dataset in conjunction with these monitored environmental inputs, a long term corrosion rate model for bridge wires has been developed that is capable of capturing variability associated with these environmental parameters.
This long term corrosion rate model is then applied to establish a methodology that will allow bridge owners and engineers to estimate the remaining strength of a main cable at any point in time. This is accomplished through the use of continually monitored environmental parameters which are input into the corrosion rate model. Incorporating the long term corrosion rate model developed in this thesis with current strength estimation techniques, the methodology presented in this thesis for the estimation of the remaining strength of suspension bridge cables may be readily adapted to other bridges and can be used to complement the current best practices for bridge inspection.
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A study of solidification dynamics with liquid mass influxThirunavukarasu, Balamurugesh 07 April 2003 (has links)
A computational model is developed to study the effects of alumina layer formation
on an ablative surface when exposed to high temperature particle laden gas
flow. The solidification dynamics i.e., the solid and liquid alumina layer growth rate,
and the heat transferred to the ablative surface are investigated. A one-dimensional
model is developed taking into consideration the thermal loading, particle loading
and the temperature dependence of the thermo-physical properties of alumina. A
fully implicit finite volume method is used to solve the coupled set of non-linear heat
conduction equations. The solidification interface is tracked using the Lagrangian
interpolation technique. The particle mass flux was found to be the major factor
affecting the solid layer growth rate. The gas heat flux also has a major effect on
the solid growth rate and the heat transferred to the ablative surface, but only for
lower particle mass fluxes. On other hand the particle temperature has a linear
effect on the solidification dynamics and the heat transferred to the ablative surface
for all particle mass fluxes. The heat transferred to the ablative surface is reduced
by approximately 39% to 88%, depending on the mass fluxes, due to the formation
of the alumina layer. / Graduation date: 2003
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A nonlocal damage theory for laminated plate with application to aircraft damage toleranceNahan, Matthew F. 02 July 1997 (has links)
Design of commercial aircraft structure, composed of composite material, requires the
prediction of failure loads given large scale damage. In particular, a fuselage of
graphite/epoxy lamination was analyzed for damage tolerance given a standard large
crack that severed both skin and internal structure. Upon loading, a zone of damage is
known to develop in front of a crack-tip in composite laminates; and, its material
behavior within the damage zone is characterized as strain softening. This investigation
sought to develop a computational model that simulates progressive damage growth and
predicts failure of complex laminated shell structures subject to combined tensile and
flexural load conditions. This was accomplished by assuming a macroscopic definition
of orthotropic damage that is allowed to vary linearly through the shell thickness. It was
further proposed that nonlocal plate strain and curvature act to force damage growth
according to a set of uniaxial criteria. Damage induced strain softening is exhibited by
degradation of laminate stiffness. An expression for the damage reduced laminated
plate stiffness was derived which assumed the familiar laminated plate [AM] stiffness
matrix format. The model was implemented in a finite element shell program for
simulation of fracture and evaluation of damage tolerance. Laminates were characterized
for damage resistance according to material parameters defining nonlocal strain and
the damage growth criteria. These parameters were selected using an inverse method to
correlate simulation with uniaxial strength and fracture test results. A novel combined
tension-plus-flexure fracture test was developed to facilitate this effort. Analysis was
performed on a section of pressurized composite fuselage containing a large crack.
Good agreement was found between calculations and test results. / Graduation date: 1998
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Analysis of a Darcy-Stokes system modeling flow through vuggy porous mediaLehr, Heather Lyn 28 August 2008 (has links)
Not available / text
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Simulating fluid flow in vuggy porous mediaBrunson, Dana Sue 28 August 2008 (has links)
Not available / text
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Contaminant induced flow effects in variably-saturated porous mediaHenry, Eric James. January 2001 (has links)
Dissolved organic contaminants that decrease the surface tension of water (surfactants) can have an effect on unsaturated flow through porous media due to the dependence of capillary pressure on surface tension. One and two-dimensional (1D, 2D) laboratory experiments and numerical simulations were conducted to study surfactant-induced unsaturated flow. The 1D experiments investigated differences in surfactant-induced flow as a function of contaminant mobility. The flow in a system contaminated with a high solubility, mobile surfactant, butanol, was much different than in a system contaminated with a sparingly soluble, relatively immobile surfactant, myristyl alcohol (MA). Because surface tension depression caused by MA was confined to the original source zone, the MA system was modeled using a standard unsaturated flow model (HYDRUS-1D) by assigning separate sets of hydraulic functions to the initially clean and source zones. To simulate the butanol system, HYDRUS-1D was modified to incorporate surfactant concentration-dependent changes to the moisture content-pressure head and unsaturated hydraulic conductivity functions. Following the 1D study, a two-dimensional flow cell (2.4 x 1.5 x 0.1 m) was used to investigate the infiltration of a surfactant contaminant plume from a point source on the soil surface, through the vadose zone, and toward a shallow aquifer. Above the top of the capillary fringe the advance of the surfactant solution caused a drainage front that radiated from the point source. Upon reaching the capillary fringe, the drainage front caused a localized depression of the capillary fringe and eventually a new capillary fringe height was established. Horizontal transport of surfactant in the depressed capillary fringe caused the propagation of a wedge-shaped drainage front in the downgradient direction. The numerical model HYDRUS-2D was modified to account for surfactant concentration-dependent effects on the unsaturated hydraulic functions and was successfully used to simulate the surfactant infiltration experiment. The extensive propagation of the drying front and the effect of vadose zone drainage on contaminant breakthrough time demonstrate the potential importance of considering surface tension effects on unsaturated flow and transport in systems containing surface-active organic contaminants or in systems where surfactants are used for remediation of the vadose zone or unconfined aquifers.
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Simulation of forming process of contour sensitive partAdegbola, Taoreed Adesola. January 2010 (has links)
M. Tech. Mechanical Engineering. / Shows Drape simulation software tool to simulate a digital standard for real life production of contour sensitive parts with CFRC materials in the aerospace and manufacturing industries.
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Characterizations and design of planar optical waveguides and directional couplers by two-step K+ -Na+ ion-exchange in glassAlbert, Jacques January 1987 (has links)
Planar optical waveguides fabricated by K$ sp+$-Na$ sp+$ ion-exchange in soda-lime glass substrates are investigated. / Experimental characterizations of planar waveguide with respect to a wide range of fabrication conditions have been carried out, including detailed measurements of the refractive index anisotropy resulting from the large induced surface stresses. / Parallel to this, the non-linear diffusion process of ion-exchange was simulated numerically to provide, along with the results of the characterizations, a complete description of the refractive index profile from any set of fabrication conditions. / The magnitude of the maximum surface index change observed was shown theoretically to be almost entirely due to the induced stress at the surface of the substrate, arising from the presence of the larger potassium ions. / Finally, a novel class of single-mode channel waveguides, made by a "two-step" ion-exchange was analyzed. A simple model for these waveguides was developed and used in the design of two directional coupler structures which were fabricated and measured. / The two-step process was conceived because it relaxes waveguides' dimensional control, yielding single-mode guides of larger size, better suited for low-loss connections to optical fibers. It also provides an additional degree of freedom to adjust device properties.
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Three-dimensional micromechanical models for the nonlinear analysis of pultruded composite structuresKilic, Mustafa Hakan 12 1900 (has links)
No description available.
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Guided mode studies of smectic liquid crystalsHodder, Benjamin January 2000 (has links)
No description available.
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