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Modeling, Simulations, and Parametric Studies of the Dip Coating Process with the Effect of Solvent Evaporation Rate and Bulk Reaction RateJittavanich, Kotchanun January 2008 (has links)
No description available.
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Thermal Management and Solidification Characteristics in High Performance Aluminum CastingSharma, Satyam January 2016 (has links)
Weight reduction in automobiles is amongst the most economical ways of reducing greenhouse gas emissions and increasing fuel efficiency. The recently invented ablation casting process is a novel technique of producing high performance light weight parts which meet this objective. In this technique a water jet demolds the water soluble sand mold and subsequently impinges upon the solidifying metal, thereby producing high cooling rates in the casting which in turn leads to microstructural refinement and higher mechanical properties.
The objective of this study was to develop a comprehensive understanding of the effect of various parameters involved in the casting of a thin walled part using the HiPerMag casting process for the wrought aluminum alloy AA 7050.
The study is divided into three major parts that deal with the composition of the sand binder system, optimization of the sand mold thickness, various aspects of the water jet parameters and the desired microstructural parameters which will result in a defect free part.
In first phase of the study, sand mold properties such as the green and dry strengths of the water soluble sand binder system used in the study were tested to ensure that they meet the molding requirements. An average green strength of 160 kPa and an average dry strength of 3825 kPa were found for the water soluble sand binder system. These values were similar to those reported in the literature for clay bonded sands and were sufficient to make molds for casting in the current study.
Secondly, a heat transfer model was developed to find a minimum mold thickness required to design a mold for the HiPerMag casting process such that the liquid metal remained sufficiently insulated before being quenched. Based on the model, for a mold with a cope thickness of 12.9 cm, the heat flux losses to the surroundings were reduced by up to 90 % versus a case where a thinner mold was used.
In addition, an analytical solution was derived for the mold thickness problem from which it was found that at a distance of 10 cm from the mold cavity there was a negligible increase in temperature of the sand at that location at large times.
Further, the minimum mold thickness was determined based on the temperature profile in the sand mold during the HiPerMag casting process. This study showed that a thin mold of about 2 cm thickness was sufficient to provide insulation to the hot metal during the HiPerMag casting process.
Thirdly, it was found that, based on cooling curve data and microstructural analysis, that a jet spacing of 15.3 cm and a time delay of 7.4 s between successive jet activations starting from the farthest jet (located near the edge of the casting), was necessary to obtain a single solidification front throughout the casting. This also ensured that grain size variation in the casting was less than 10 μm for having uniform mechanical properties.
Also, it was found for a thin walled casting, the amount of solid present in the solidifying casting at the time of water jet impingement had a negligible effect on the movement of the solidification interface.
Finally, the effect of jet momentum on surface defects was examined. It was determined that the maximum jet momentum resulting in no surface defects at temperatures close to the liquidus for Al AA 6061 alloy was approximately 2 kg.m/s. / Thesis / Master of Applied Science (MASc)
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DESIGN AND OPTIMIZATION OF A STRIPLINE RESONATOR SENSOR FOR MEASUREMENT OF RUBBER THICKNESS IN A MOVING WEBBhuiya, Md. Omar F. January 2006 (has links)
No description available.
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The role of adhesive resin luting agents in crown retentionOsman, Saad AbuBakr January 2000 (has links)
No description available.
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Lithospheric flexure and the evolution of Australian basinsHaddad, David January 1999 (has links)
No description available.
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Influence of variations in ceramic thickness and bonding substrate on the fracture resistance of lithium disilicate restorationsvan Lierop, Jean January 2017 (has links)
Magister Scientiae Dentium - MSc(Dent) / Restorative dentistry aims to replace lost or damaged tooth structure with
durable and life-like alternatives. To accommodate the inherent limitations and weakness of
the restorative materials, preparation techniques often require the sacrifice of healthy tooth
structure to create enough restorative space. This can lead to weakening of the remaining
tooth structure, with subsequent damage or catastrophic failure. When using indirect
restoratives, the development of adhesive luting agents (adhesive cements) and stronger allporcelain
restorations (lithium disilicate) has contributed to the development of “minimally
invasive” preparation techniques and concepts such as cavity design optimization (CDO) and
bio-substitution. With these techniques, resin materials are combined with ceramic
restoratives in an attempt to not only produce strong restorations, but also increase the
longevity of the remaining tooth. The clinician needs to therefore find the ideal preparation
design that combine such materials to produces a clinically performing restoration while
increasing the strength and longevity of the underlying tooth.
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Experimental and numerical investigation of the thickness effect in the ductile tearing of thin metallic platesHachez, Frédérique 18 April 2008 (has links)
The aim of this thesis is to propose a more general understanding of the influence of the thickness of the plate and of the microstructural and mechanical properties of the material on the resistance to ductile tearing in thin metallic plates. The objective is to attempt unifying different observations made in the literature together with the results of a new extensive experimental campaign. The final goal is to develop predictive simulation tools with a micromechanics-based foundation.
In order to reach this objective, a detailed experimental campaign has been performed concerning the fracture behavior of the aluminium alloy 6082, complemented by experiments on a stainless steel A316L and on a set of 14 other materials.
In a first modelling effort, we propose very simple closed-form models in order to separate the different contributions to the total work of fracture in thin plates: the work of necking and the work of damage and material separation. The
respective contributions are compared and an unique explanation of the different behaviors observed experimentally is proposed.
In a second modelling step, we develop a full 3D numerical tool based on cohesive elements for simulating crack propagation in thin ductile plates. Three different methods are proposed to calibrate the parameters of the model in order
to reproduce the experimental data and to extrapolate the results to other material
properties or geometric conditions. Finally, the parameters of the cohesive zone model are justified using micromechanics-based arguments. / Le but de cette thèse est de proposer un modèle général à base micromécanique
permettant de comprendre l’influence de l’épaisseur de la tôle ainsi que de la
microstructure et des propriétés mécaniques du matériau sur la résistance à la
rupture ductile de plaques minces métalliques. L’objectif est d’essayer d’unifier
les différentes observations de la littérature ainsi que les résultats d’une nouvelle
campagne expérimentale afin d’aboutir au développement d’outils numériques
prédictifs.
Pour atteindre cet objectif, nous avons réalisé une campagne d’essais concernant
le comportement à la rupture de différents matériaux. Cette campagne a été
menée en profondeur sur l’alliage d’aluminium 6082 et de manière moins approfondie
sur un acier inoxydable A316L ainsi que sur 14 autres matériaux.
Dans un premier temps, nous présentons une série de modèles semi-analytiques
simples dont le but est de séparer les différentes contributions au travail de rupture
total dans les tôles minces : le travail de striction et le travail d’endommagement
du matériau. Ces deux contributions sont ensuite comparées et nous proposons une
explication qui reprend les différents comportements observés expérimentalement.
Dans un deuxième temps, nous développons un outil numérique 3D complet destiné à simuler la propagation de fissures dans les tôles minces ductiles et qui utilise
des éléments cohésifs. Trois méthodes différentes sont proposées pour calibrer les
paramètres du modèle de manière à reproduire les données expérimentales et à
permettre l’extrapolation des résultats à d’autres matériaux ou d’autres épaisseurs
de tôles. Finalement, les paramètres du modèle de zone cohésive sont justifiés grâce
à des arguments à fondement micromécanique.
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Characterization of Ultrasound Elevation Beamwidth Artefacts for Brachytherapy Needle InsertionPEIKARI, MOHAMMAD 01 September 2011 (has links)
Ultrasound elevation beamwidth is the out of plane thickness causing image artefacts
normally appearing around anechoic areas in the medium. These artefacts could also
cause uncertainties in localizing objects (such as a surgical needle) in the ultrasound
image slices. This thesis studies the clinical significance of elevation beamwidth artefacts
in needle insertion procedures. A new measurement device was constructed to
measure the transrectal ultrasound elevation beamwidth. The beam profiles of various
lateral and axial distances to the transducer were generated. It is shown that
the ultrasound elevation beamwidth converges to a point within its focal zone close
to the transducer. This means that the transrectal ultrasound images have the best
resolution within the focal zone of the ultrasound close to the transducer. It is also
shown that the ultrasound device settings have a considerable impact on the amount
of beamwidth artefacts. Needle tip localization error was examined for a curvilinear
transrectal ultrasound transducer. Beveled prostate brachytherapy needles were inserted
through all holes of a grid template orthogonal to the axial beam axis. The
effects of device imaging parameters were also investigated on the amount of localization
error. Based on the developed results, it was found that the imaging parameters
of an ultrasound device have direct impact on the amount of object localization error
from 0.5 mm to 4 mm. The smallest localization error occurs laterally close to the center of the grid template, and axially within the beam’s focal zone. Similarly, the
largest localization error occurs laterally around both sides of the grid template, and
axially within the beam’s far field. Using the ultrasound device with appropriate
imaging settings could minimize the effects of these artefacts. We suggest to reduce
the gain setting of the ultrasound device. This will reduce the energies assigned to
the off-axis beams and as a result, the elevation beamwidth artefacts are minimized. / Thesis (Master, Computing) -- Queen's University, 2011-09-01 15:27:43.098
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The hydrodynamics of thin liquid films flowing over a rotating discWoods, William Paul January 1995 (has links)
This study is concerned with flow and stability of thin liquid films flowing over the surface of a disc rotating about a vertical axis. The work consists of a theoretical and experimental investigation into the flow of the steady-state film, and the waves which occur on it. The theoretical model is investigated in its steady-state form (no waves present) using both asymptotic and numerical techniques. The unsteady problem is also examined, using asymptotic methods, for the inception and propagation of waves of small amplitude with respect to the mean film thickness. The experimental investigation employs a light absorption technique to obtain accurate film thickness measurements across individual three dimensional wave profiles. The results are used to test the validity of the small amplitude assumption of the theoretical model, which is found to be restrictive, and to give both qualitative and quantitative data about the large amplitude waves that are often observed.
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Late quaternary evolution of Reedy Glacier, Antarctica /Todd, Claire E. January 2007 (has links)
Thesis (Ph. D.)--University of Washington, 2007. / Vita. Includes bibliographical references (leaves 113-116).
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