No description available.

No description available.

This work investigates the behaviour of clay in a commercial screw driven extruder used to manufacture clay drainage pipes.  Based on a striping effect observed within the clay during extrusion, experiments and models have been constructed to determine if these stripes can be removed.  The aim is to improve product yield and reduce waste. During the course of this work, it will be described how it is believed that the stripes are the result of localisation and shear banding which allows water to evaporate quicker from some areas than others, causing stripes.  Some preliminary work is discussed regarding a hopper, used as a step towards generating models for the extruder.  Latter sections detail the models created using various mathematical techniques which are used to simulate the material as it flows through the system.  Of particular relevance is optimisation theory which allows various parameters to be determined based on a pre-determined function and a set of initial guesses.  Building upon this work leads to the conclusion that modifying the design of both the auger and extension can reduce the chances of localisation, thereby reducing the chances of stripes forming. Finally, a set of recommendations are made regarding potential design changes, and a complete redesigned system is proposed as an example of what would be required.

In view of the fact that clay has not been used so extensively or wisely in elementary art education as the generally recognized importance of the material seems to justify, the purpose of this study is to explore the possibilities of clay as a creative medium and to determine which of the many ceramic techniques are most suitable for use by pupils in the upper elementary grade.

The present study of an ideal mixture for thrown ware is an outgrowth of a long-time personal interested developed during undergraduate work at North Texas State University. While a natural earthenware clay proved to be the best all-purpose clay for class use, it was not ideal for throwing.

Neste trabalho foram preparados nanocompósitos de Poliestireno (PS) e argilas organofílicas. As argilas, inicialmente hidrofílicas, foram modificadas organicamente utilizando três sais quaternários de amônio diferentes: Cloreto de hexadecil trimetil amônio (CTAC), Cloreto de alquil dimetil benzil amônio (Dodigen) e Cloreto de dimetil dioctadecil amônio (Praepagen). A argila organofílica Cloisite 20A foi também utilizada neste estudo. Os nanocompósitos foram preparados por intercalação no polímero fundido por três técnicas diferentes: adição de argila em suspensão de álcool etílico por uma bomba dosadora de líquidos durante a extrusão, adição de argila em pó por um alimentador mecânico durante a extrusão e adição de suspensão de argila em álcool etílico durante obtenção por batelada. Os materiais obtidos foram caracterizados por difração de raios-X (DRX), microscopia óptica (MO) e microscopia eletrônica de transmissão (MET) e ensaios reológicos de Cisalhamento Oscilatório de Pequenas Amplitudes (COPA). As propriedades térmicas foram analisadas por análise termogravimétrica (TG) e as propriedades mecânicas foram analisadas por ensaios de tração e impacto Izod. As três técnicas se mostraram eficazes na preparação dos nanocompósitos, e seus resultados apresentaram uma similaridade muito grande. Os resultados de DRX e microscopia mostraram que a maioria dos nanocompósitos apresentou estruturas compostas de fases intercaladas e esfoliadas. As análises térmicas mostraram que a adição de argila ao PS o tornou mais estável termicamente, suportando maiores temperaturas antes de iniciar o processo de degradação. Os ensaios reológicos de COPA e ensaios mecânicos dos nanocompósitos obtidos não apresentaram grandes variações em relação ao PS puro. / In this work nanocomposites of polystyrene (PS) and organophilic clays were prepared. The clays were organically modified using three different ammonium quaternary salts: cetyltrimethyl ammonium chloride (commercial name: CTAC), alquildimethyl benzyl ammonium chloride (commercial name: Dodigen) and distearyl dimethyl ammonium chloride (commercial name: Praepagen). The organoclay Cloisite 20 A was also used in this work. The nanocomposites were prepared by melt intercalation using three different techniques: adding the organoclay as a diluted organic solvent supension to the extruder using a motor-driven metering pump, adding the organoclay as powder to the extruder using a mechanical feeder and adding the organoclay as a diluted organic solvent suspension to the mixer. The materials obtained were characterized by X-ray diffraction (XRD), optical microscopy (OM), transmission electron microscopy (TEM) and by rheological studies through small amplitude oscillatory shear tests (SAOS). The thermal properties were studied by thermogravimetrical analyses (TG) and the mechanical properties were studied by tensile and impact Izod strength tests. The three techniques were efficient to prepare nanocomposites, and their results were very similar. The DRX and microscopy results showed that the most nanocomposites presented structures composed by intercalated and exfoliated phases. The thermal analyses showed that the addition of organoclay turned PS more thermally stable, increasing their degradation temperatures. The results of rheological studies (SAOS) and the mechanical tests did not present significant variations compared to the neat PS.

acase@tulane.edu / It is of paramount importance to me as a maker to marry art and craft within the confines of function. I make porcelain objects with specific physical uses in mind. I develop my work to address aspects of aesthetics and design simultaneously. The relationship we have with handmade pottery is unlike that of other art objects. It is personal, relational, and intimate. As such, I create sculptural vessels intended for physical use. I draw great inspiration from the natural world. My vessels are imbued with volume, and are reminiscent of organic life forms. I am fascinated with the plumpness of sea tunicates, flower ovaries and seed pods. I am intrigued by the ethereal depth of cloud formations. I heavily manipulate my wheel thrown forms by hand to incorporate a quality of pillowy fullness within an organized but imperfect formal structure. I stretch and push the clay into billows, and bind these structures with a criss-crossing of geometric lines to create convex swells within the walls of each vessel. I glaze each piece to accentuate the form, and have utilized colors from the natural world that complement the external curves of the vessels. As a functional artist, I strive for the vessels that I create to have a dual purpose. We fill our lives with objects; I want my contribution to our world to be simultaneously elegant and utilitarian. / 1 / Danielle B. Inabinet

No description available.

The effective shear strength of artificially overconsolidated clays with continuous fissures, or with discontinuous or partial fissuring, has been discussed from both the experimental and numerical points of view.Direct shear and triaxial tests have been conducted on a range of unfissured, partially and fully fissured specimens of artificially overconsolidated clay samples in the laboratory. Specimens subjected to direct shear tests have been prepared in three different preconsolidation pressures and two or three different Overconsolidation ratios (OCR) for unfissured, partially and fully fissured specimens. Specimens subjected to triaxial tests also were prepared for three different preconsolidation pressures and overconsolidation ratios. In order to investigate the effect of orientation of fissures, artificially overconsolidated fissured triaxial specimens were prepared in three different orientations at 30 degrees, 45 degrees and 60 degrees to the direction of minimum principal stress (sigma[subscript]3).For both direct shear and triaxial tests, special tools and devices were designed and constructed to prepare unfissured, partially and fully fissured specimens.Taking into account the number of parameters which influence the effective shear strength of overconsolidated clays, and the time which is needed to artificially prepare the overconsolidated specimens and to run drained tests, as well as the impossibility or impracticality of the laboratory simulations for some specific cases, numerical methods were used to complement the experimental component of the investigation.Numerical modelling of direct shear and triaxial specimens utilised the FLAC (Fast Lagrangian Analysis of Continua, Itasca, 1993) program for two dimensional simulation of the direct shear tests and the ANSYS (1996) program for three dimensional simulation of triaxial tests. The experimental ++ / results have been used to calibrate the coefficients of the numerical models and to verify the results obtained from numerical models.Strain softening behaviour was simulated numerically for unfissured and fully fissured specimens subjected to direct shear tests. Using the obtained experimental and numerical results of the study of direct shear tests with respect to the effects of different parameters on the effective shear strength of the spacing subjected to direct shear tests and also FLAC programming, FLACish (FISH), a model was written designated as the Homogenised Strain Softening Model (HSSM). In this model the effects of different parameters discussed in this thesis, are applied to the Mohr Coulomb parameters (c'[subscript]u and phi'[subscript]u) of unfissured specimens. This model was used to predict the effective shear strength of cases in which laboratory simulation was impractical or not feasible.The advantage of this model (HSSM) is that it relates the effective shear strength of the fissured mass to the corresponding Coulomb parameters (c'[subscript]u and phi'[subscript]u) of the intact or unfissured overconsolidated clay specimen with reduction functions relating to the parameters discussed in this thesis.The numerical models developed by ANSYS were calibrated and verified by the experimental results, and then used to predict or estimate the effects of confining pressure, orientation of fissures on the three dimensional modelling of the partially and fully fissured overconsolidated triaxial specimens.In this thesis the effects of the type of clay, preconsolidation (P'[subscript]c) pressure, Overconsolidation ratio (OCR), size of sample, rate of shearing and fissure parameters, such as spacing, width and orientation of fissure were discussed and identified or quantified to estimate the effective shear strength of the artificially overconsolidated ++ / fissured samples. These results are applicable for the estimation of the effective shear strength of the naturally overconsolidated fissured mass by homogenising the effects of the parameters on the Mohr Coulomb parameters (c'[subscript]u and phi'[subscript]u) of the intact or unfissured clay mass.

The erosion behaviour of clay soils has been investigated through a comprehensive program of laboratory testing. Three different erosion test methods have been employed including the rotating cylinder test (RCT), the hole erosion test (HET), and the slaking test (SLT). A new rotating cylinder test device is designed and manufactured capable of testing disturbed and undisturbed soil samples in saturated and unsaturated states. Details of the equipment along with its calibration, testing and sampling procedures are provided. The HET has been reviewed and modified to provide consistent test results. In addition, the slaking test has been customised to accept samples identical to those used in the RCT. A total 111 RCT, 139 HET, and 108 slaking tests have been conducted and analysed. Typical shapes of the erosion curves are identified, based on a wide range of shear stresses and erosion rates analysed. Correlations are presented between the RCT and HET, and between the RCT and SLT to allow characterisation of clay soil erosion in a consistent and unified manner. The erosion modes of clay soils are investigated and categorised into three main groups: ???dispersive erosion???, ???saturated non-dispersive erosion???, and ???unsaturated non-dispersive erosion???. It is shown that soils falling in the same category exhibit near identical erosion characteristics. Factors affecting clay soil erodibility are investigated and displayed for each erosion mode. All findings are presented in a unified framework. A suggested procedure is provided for the evaluation erosion potential in clay soils for practical applications.