Showing papers on "Deformation (meteorology) published in 1987"

Deformation processes in unconsolidated sands

Abstract: Summary Deformation in unconsolidated sands requires the action of a deformation mechanism to reduce sediment strength and a driving force to induce deformation. Deformation mechanisms include liquefaction and fluidization and are reflected in the style of deformation and grain orientation fabrics. They are initiated by a trigger, including groundwater movements, wave action and seismic shaking. Driving forces include gravitational body force, unevenly distributed loads, unstable density gradients and shear forces, and are reflected in the geometry of deformation. These components are combined to produce a genetic classification of soft-sediment deformation processes and structures.

Apparatus for analysis of failure of material

Abstract: Apparatus is provided for performing mechanical deformation studies of a sample of material to determine mechanical and petrophysical properties of such a sample. The apparatus is useful in conjunction with an imaging (NMR or CAT) apparatus.

Kinetic model for tensile deformation of polymers

Abstract: Deformation de polymeres flexibles solides. Modele base sur la theorie de vitesse d'activation chimique d'Eyring. Application au polyethylene cristallise a l'etat fondu

Band-edge hydrostatic deformation potentials in III-V semiconductors

Abstract: We report experimental values for the band-edge hydrostatic deformation potentials of GaAs and InP semiconductors. The deformation potentials are determined directly by observation of the universal pressure derivative of transition-metal defect levels and consideration of this pressure derivative in the context of recent models of heterojunction band lineup. We obtain values of -9.3 and -7.0 eV for the conduction-band deformation potentials of GaAs and InP, respectively, determined from the uniaxial-stress deep-level transient spectroscopy on defect levels of Ti and V.

The Effects of Disequilibrium and Deformation on the Mineralogical Evolution of Quartz Diorite During Metamorphism in the Eclogite Facies

Abstract: In the Sesia Zone, Western Alps, a large volume of orthogneiss formed as a result of eclogite fades metamorphism and deformation of quartz diorite during early Alpine underthrusting and subduction. Rare lenses of undeformed metaquartz diorite, preserved within the orthogneiss, represent an early stage in the evolution of this latter rock type. The metamorphic and microstructural evolution of the orthogneiss in the eclogite fades has been reconstructed from studies of gradational contacts between undeformed and strongly deformed rocks. High pressure transformations of the original igneous plagioclase + biotite + quartz assemblage to jadeitic pyroxene (Jd0.95_0.83) + zoisite + quartz + garnet + 2 muscovites developed prior to deformation. Slow intergranular diffusion resulted in a state of disequilibrium between small textural domains in the metaquartz diorite. The compositions of the phases of the undeformed metaquartz diorite do not reflect the bulk rock composition, but were controlled by their position relative to reactant phases. The jadeitic pyroxenes, for example, formed in localized domains which originally consisted of sodic plagioclase whereas omphacite was the equilibrium pyroxene for the bulk rock composition. Mineralogical changes which occurred during subsequent deformation of the metaquartz diorite are interpreted as resulting from a progressive enlargement of equilibrium domains and the partial equilibration of mineral compositions to the bulk rock composition rather than from changes in pressure and temperature. Initially during high-strain deformation, fine-grained aggregates of jadeitic pyroxene + quartz + zoisite (originally pseudomorphing plagioclase) are inferred to have deformed by a mechanism of grain boundary sliding accommodated by diffusive mass transfer. Muscovite and garnet compositions homogenized during the deformation but due to slow intracrystalline diffusion, pyroxene compositions (Jdo.9J_0.go) remained metastable. The coarsening of pyroxene eventually terminated deformation by grain boundary sliding and this mineral subsequently deformed by intracrystalline plastidty. This latter process was accompanied by and perhaps catalysed a change in pyroxene composition from metastable jadeite towards omphacite by a reaction involving the resorption of garnet and the nucleation and growth of paragonite. The resulting orthogneiss consists of quartz -Iomphadte + garnet + phengite + paragonite + zoisite. The rock is characterized by a broad range of pyroxene compositions (Jdo.8_O5) due to the incomplete equilibration of this mineral to the bulk rock composition and a lack of Fe-Mg exchange equilibrium between pyroxene and garnet. However, in contrast to the undeformed metaquartz diorite, there are no obvious textural indications of disequilibrium between phases in the orthogneiss.

Patterned float glass method

Abstract: Patterned float glass is produced without distorting patterns imparted to the surface by forming the glass by a process that avoids deformation of the glass subsequent to the pattern imparting step.

Deformation of Scottish Quaternary sediment sequences by strong earthquake motions

Abstract: Summary Deformed Quaternary sand, silt, clay and peat sequences from four localities in Scotland are interpreted as seismites by the deformation history of liquefied, fluidized, slumped, and faulted units, and by comparison with seismites documented elsewhere. Two of the sequences consist of outwash sands and silts, deposited during the recession of the Devension ice cap in the region of Perth. Other deposits consist of glacial sands and interglacial peats in the Western Highlands, and glacio-lacustrine silts in the Glen Roy area; both probably deposited during the late stages of the Loch Lomond Readvance. Careful evaluation of internal geometries and deformation sequences reveals an intimate association of ball-and-illow, fluidization, dish, load, flame and ‘fault-grading’ structures which are most satisfactorily explained by prolonged ground shaking produced by shallow earthquakes. In some cases, potential fault sources for the inferred earthquakes have been identified.

Changes of soil water suction, conductivity and dry strength during deformation of wet undisturbed samples

Abstract: Deformation (without failure along local shear-planes) of wet clayey soil during tillage and traffic operations can cause significant undesirable changes in soil physical properties, even though it is not generally accompanied by severe compaction. Field conditions were simulated by deforming wet, dense, unsaturated, cylindrical field samples in quick (or undrained) triaxial tests. In these tests, soil samples were compressed to half their initial height, which was accompanied by large lateral expansion. Soil water suction (at constant water content) typically increased from 5 to 30 kPa and air and water transmission characteristics dramatically decreased with deformation. The soil water suction increase occurred at a nearly constant degree of saturation, which may explain the often observed phenomenon of soil adhering to tool and tyre surfaces. Deformation doubled tensile strength after drying. Deformability was characterized by a coefficient of viscosity and a threshold shear stress, typical values being 7·10 6 mPa.s and 6·10 7 mPa, respectively.

Slump strain in the Tertiary of Cyprus and the Spanish Pyrenees. Definition of palaeoslopes and models of soft-sediment deformation

Abstract: Summary Slumps exposed in Tertiary sediments in Cyprus and the Spanish Pyrenees vary in inferred translation distance from metres to hundreds and possibly thousands of metres. Contractional strain initiates open to tight upright to inclined folds with hinges that are sub-parallel to the strike of the palaeoslope. This strain is produced mainly by pure shear layer parallel shortening as the slump detachment propagates, but may involve a component of simple shear strain. Downslope translation of the failed unit commonly imparts a simple shear strain which tends to tighten folds and rotate fold hinges and fold axial surfaces. Fold hinges rotate towards the downslope direction, and fold axial surfaces rotate towards parallelism with the upper and lower surfaces of the slump. Coaxially refolded folds and sheath folds may also develop. Steeply plunging folds may initiate in slumps, due to the development of steeply dipping shear zones with margins sub-parallel to the downslope direction which accommodate differential downslope movements of segments of the slump. Fold axial surface attitude and fold profile may be used as a rough estimate of the degree of fold rotation.

High temperature creep of WC-Co alloys

Abstract: The high temperature deformation of tungsten carbide-cobalt composites has been performed in the 1050 to 1350° C temperature range either in compression or in three point bending. The creep behaviour of these materials exhibits a sigmoidal log $$\mathop \varepsilon \limits^ \circ - log$$ σ plot with three domains of steady state creep rate possessing a different value of the stress exponent. From recent microscopical and analytical results a microstructural model of the composite is proposed. This model assumes the existence of carbide chains formed of crystals linked with coincidence grain boundaries and takes the number of coincidence grain boundaries into account. It has been used to interpret the creep results. The controlling component of the composite is the tungsten carbide and two deformation processes, grain boundary sliding and intragranular deformation, are the main mechanisms which are involved in the explanation of the creep behaviour. The results of the creep tests are discussed in correlation with transmission electron microscope (TEM) investigations on annealed then deformed samples. TEM microstructural studies of the carbide phase after deformation show an extensive intragranular deformation which has been carefully analysed. Attention has also been paid to the defect structure of grain boundaries.