Inaug.-Diss.--Zürich. / Vita. Bibliography: p. 40-43.

Thesis (M.S.)--University of Wisconsin--Madison. / Typescript. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 59-61).

The adhesion theory of friction is investigated using the model junction proposed by A. P. Green in 1954. The results of the model junction experiments are extended to study the wear mechanism. An attempt has been made to correlate the model junction results with similar results obtained by various experimentors using actual surfaces. The friction results established that friction is independent of load which is in agreement with experiments done using actual surfaces. The model junction shows general agreement with the theoretical estimate of the friction and normal forces made by A. P. Green. The wear results indicate general correlations between the model and actual surfaces with regard to particle shape and wear-load relationships. In general, the results of the investigation indicate that actual surfaces should have small surface finish angles for minimum wear and that the double shear mode of junction failure provides an explanation for wear particle formation and the large values of the coefficient of friction found for outgassed metals sliding in vacuo. / Applied Science, Faculty of / Mechanical Engineering, Department of / Graduate

The deformation behaviour of polycrystalline compacts of Mg(OH)₂ during dehydroxylation has been studied in an attempt to evaluate the nature of strain that can be introduced into the compact during the reaction. A study of neck-growth between tips of single crystals of Ca(OH)₂, and between two hemispherical tips of Mg(OH)₂, compacts showed both deformation and interaction at the contact point during the dehydroxylation reaction. Load-dependent deformation of the compacts gave a total strain proportional to the one-third power of the applied stress. The creep deformation of Mg(OH)₂ compacts during dehydroxylation was also studied under isothermal conditions. The overall creep behaviour can be divided into three stages. The initial stage is initiated by the dehydroxylation reaction. During the second or steady state creep stage the highest creep rate was obtained. The steady state creep rate was determined as a function of temperature pressure, and relative density of the green compact. The results are represented by: [formula omitted] Particle sliding was considered to be the most probable mechanism for creep during the second stage. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

Ce travail vise à mieux comprendre les interactions entre couplage, glissement lent et rupture sismique en contexte de subduction. L’objet d’étude est la subduction Nord Chili–Sud Pérou, qui a été reconnue comme une lacune sismique et qui a fait l’objet d’un important effort international d’instrumentation géophysique. Cette zone a été affectée par tremblements de terre qui ont été bien enregistrés, ce qui en fait une cible bien adaptée pour étudier les mécanismes de préparation des grands séismes de subduction, et le lien entre couplage, glissements lents et rupture sismique.Les 65 stations GPS installées dans la zone ont été traitées en doubles différences avec le logiciel GAMIT-GLOBK sur la période 2000-2014. Les séries temporelles de position obtenues ont été analysées et les déplacements associés aux différentes phases du cycle sismique et aux mouvements saisonniers ont été modélisés.L’analyse des tendances dans les séries temporelles GPS ont permis de mettre en évidence un changement de vitesse intersismique avant et après le séisme en slab-pull de Tarapacà de juin 2005, dans la région qui a été rompue par le séisme d’interface d’Iquique en 2014. Ce changement de vitesse est associé à un changement de taux de sismicité superficielle et profonde. Le déclustering du catalogue sismique indique que ce changement de taux, affecte aussi la sismicité de fond, caractéristique du taux de chargement. Nous avons pu mettre en évidence que des interactions existent entre sismicité profonde et superficielle, et pourraient jouer un rôle important dans la préparation des grands séismes d’interface. A plus courte échelle de temps, les séries temporelles montre un autre changement de vitesse 8 mois avant le séisme d’Iquique. La modélisation indique que ce changement correspond à un glissement lent de Mw 6.5, essentiellement asismique, correspondant à la phase de nucléation long-terme de ce tremblement de terre.Nous avons également analysé les variations court terme dans les signaux non-modélisés des séries temporelles GPS, qui ont permis d’identifier, grâce à une méthode de Template Matching 48 petits événements de glissement lent pendant la période de chargement intersismique. Ces événements sont basés pour leur grande majorité en dessous de la zone sismogénique dans des zones de couplage très faible, ou de couplage intermédiaire, indiquant que le glissement se fait par relâchements successifs. Souvent ces événements transitoires sont corrélés à des pics d’activité sismique, notamment profonde.La cinématique de la source du séisme d’Iquique et de sa plus grosse réplique a été étudiée en combinant données GPS à haute fréquence et données accélérométriques. Les déplacements statiques ont été inversés pour caractériser la répartition du moment géométrique. Cette source statique a ensuite été utilisée comme prior pour une séquence d’inversions cinématiques en fréquence. Les résultats montre que ces deux séismes présentent une distribution de glissement bimodale, segmentée selon la profondeur. L’extension latérale du choc principal correspond à celle d’un bassin submergé d’avant arc associé à une anomalie de gravité, et pourrait être contrôlée par les structures tectoniques de la croûte supérieure. La réplique principale est située dans une zone de changement de contrainte de Coulomb induit par le choc principal, ce qui suggère qu’elle a été déclenchée par celui ci.Grâce à une combinaison de données géodésiques et sismologiques, ce travail offre donc une vue détaillée des processus en jeu au cours du séisme d’Iquique et des décades qui l’ont précédé. Les perspectives de recherches soulevées par ce travail sont nombreuses, notamment sur les possibilités d’observations raffinées des phénomènes associés au cycle sismique et à la préparation des grands tremblements de terre de subduction. / The aim of this Ph.D. thesis is to have a better comprehension of the interactions between coupling, slow slip events (SSEs) and the seismic ruptures in subduction zones. This work focuses on the North Chile - South Peru subduction zone that has been recognized as a mature seismic gap. Thus, the region has been the target of an important international effort in geophysical instrumentation (GPS and seismological stations), since the mid-2000s. The region has been affected by several well-registered earthquakes, that makes it good case to study the earthquake preparation phase and the relationship between coupling, SSE and seismic rupture.The 65 stations available in the region have been processed in double differences using the GAMIT-GLOBK software in the period 2000-2014. The GPS displacement time series have been analyzed and the associated displacements to the different stages of the seismic cycle as well as seasonal signals have been modeled.The analysis of the tendencies in the GPS time-series evidences a change in the velocity field before and after the Tarapaca slab-pull earthquake occurrence in June 2005, in the range of latitude affected by Iquique earthquake in 2014. This velocity change is associated with a change in the shallow and deep seismicity rates. The analysis of the declustered catalog shows that the velocity change observed affects the background seismicity as well, that often seen as a proxy for the tectonic loading. Finally, we find interactions between shallow and deep seismicity, that may play an important role in the interface earthquakes preparation phase. At a shorter time scale, the time series show another change in velocity 8 months before Iquique earthquake. Models indicate that the velocity change corresponds to an SSE Mw 6.5, mainly aseismic, corresponding to the long preparation phase of the earthquake.The short-term GPS velocity variations have also been analyzed on residual signal. It allows identifying, thanks to a matched-filter, 48 small SSEs during the interseismic period. These events are localized mostly in the deeper part of the seismogenic zone, in areas where the coupling is low or with intermediate values. It suggests that the slip in these regions is produced in burst way. Some of those events are correlated with peaks of seismic activity, especially at intermediate depths.Finally, the kinematic rupture process of Iquique earthquake process and its biggest aftershock are studied, employing a combination of high-rate GPS and strong motion data. The static displacements are inverted to characterize the slip. This static solution is used as apriori information for a sequence of kinematic inversions in the frequency domain. The results show that both events have a bimodal slip distribution, segmented along dip. The lateral extension of the mainshock is centered on a forearc offshore basin associated with a gravity anomaly, and may be controlled by tectonic structures of the upper crust. The aftershock is located in an area with strong Coulomb Stress Changes induced by the mainshock, suggesting that it was triggered by the mainshock.Thanks to the combination of geodetic and seismological data, this thesis provides a detailed vision of the processes involved during the Iquique earthquake and the previous decades. The research prospects raised by this work are numerous, particularly on the possibilities of refined observations of the phenomena associated with the seismic cycle and the preparation of large subduction earthquakes.

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In shape modeling applications, \emph{deformation} is the process of applying a continuous, non-affine transformation to a shape. The definition of the deformation should be independent of the representation of the shape. In practice, the shape is often represented by its boundary, which is defined by a set of vertices and by connectivity information. The transformation is often applied to these points. A deformation algorithm takes the orginal shape and designer's choices as inputs, and outputs the deformed shape. This dissertation dedicates to introducing \emph{spine-based deformation}: Any distortion to the shape is controlled by a low dimensional proxy, which is a spine curve or surface. Considering a sometimes important constraint to preserve the shape's volume during deformation, this thesis addresses a suite of problems in spine-based deformation with local volume preservation, meaning that the volume of any subset of the shape is preserved. Although our deformation model may be applied to the control points or vertices of a surface model that is not a water tight boundary of a solid, in this thesis, the term shape will refer to a solid model which has a clearly defined interior and volume. Previously proposed local or global volume compensation techniques are typically based on iterations that introduce a complexity bilinear in the numbers of vertices and iterations. we present a family of closed-form solutions for shape deformation with mathematically exact local volume preservation, and demonstrate their power in the context of interactive bending, rotating, sliding or stretching a 2D or 3D shape. The overall complexity is linear in the number of vertices. Proposed spine-based deformation framework adopts the following assumptions in geometric modeling: -- When the spine is a curve, a plane normal to the spine curve remains normal to the spine curve after deformation. The parameter associated with the point at which the plane intersects the curve is unchanged. -- When the spine is a surface, a line normal to the spine surface remains normal to the spine surface after deformation. The parameters associated with the point at which the line intersecting the plane remain unchanged. With these assumptions, we compute the closed-form formulation for the deformation that guarantees local volume preservation and is expressed using real roots of low degree polynomials and simple point and vector expressions. Due to its simplicity, our solution may be used to deform complex models in realtime during interactive manipulation or during animation, where the behavior of the spine has been designed or is computed in realtime through simulation.

Deformation, profile and tomography measurement is critical for engineering materials characterization and engineering structure component design, analysis and biomedical application. The current existing 3D measurement method, such as stylus based profilometry, 3D optical stereo imaging and focus stacking, either suffers from low sampling speed from spatial scanning or maximum thickness of the specimen that could be imaged due to physical constraints. This thesis is dedicated to develop a hybrid 3D measurement method that can be easily implemented with fast imaging speed for dynamic process at the microscale. Also, at the microscale, the reduced depth of focus of existing microscope system greatly limits the maximum depth of the specimen that could be imaged, especially at high magnification. In this study, a 3D tomography system will be developed with extended depth of focus and improved axial resolution.

The need to increase vehicle performance, particularly fuel efficiency, has led to an increased interest in using lightweight metals for vehicle structural components. Lightweight aluminum alloys offer the potential to significantly reduce vehicle mass when structural components that use steel are replaced. Mass reduction is a very efficient route to increase vehicle performance. In vehicles with traditional powertrains, mass reduction can increase fuel efficiency. In vehicles with electrical powertrains, mass reduction can increase driving range. Regardless of the specific structural application, the best performance of any aluminum alloy is only obtained by achieving a microstructure that produces the best material properties. For wrought aluminum alloys, hot and cold deformation steps are critical to obtaining a desirable microstructure prior to the forming of a final component. For sheet material, the first step in controlling the final microstructure is microstructure evolution during hot rolling the cast ingot material. Hot rolling precedes cold rolling of the sheet to final thickness in most commercial sheet manufacturing operations. Microstructure during hot rolling is difficult to study because it requires a combination of high temperatures, fast strain rates and large strains to do so. Furthermore, specimens for microstructural examination must be extracted from these conditions while retaining the characteristics of the specific conditions that are to be studied. Hot torsion testing is the traditional approach to meeting these experimental requirements. In this investigation, a new hot torsion testing instrument is designed, fabricated and validated to enable future experiments that will elucidate microstructure evolution under conditions pertinent to hot rolling. This new instrument is integrated with computerized control and data acquisition systems. Validation experiments were conducted to characterize its capabilities. It is concluded that the completed instrument meets the requirements necessary to study plastic deformation and microstructure evolution in aluminum alloys under conditions relevant to hot rolling. / text