Showing papers on "Deformation (meteorology) published in 1994"
TL;DR: In this paper, a canonical star product associated with any symplectic connection on a regular Poisson manifold is considered. And a trace construction of the star product is given for coefficients in the bundle Hom(£, E) of the manifold.
Abstract: A construction, providing a canonical star-product associated with any symplectic connection on symplectic manifold, is considered. An action of symplectomorphisms by automorphisms of star-algebra is introduced, as well as a trace construction. Generalizations for regular Poisson manifolds and for coefficients in the bundle Hom(£, E) are given.
946 citations
Patent•
22 Jul 1994TL;DR: In this paper, the authors describe a web material which exhibits an elastic-like behavior along at least one axis when subjected to an applied and subsequently released elongation, and the web material includes a strainable network having at least two visually distinct regions of the same material composition.
Abstract: A web material which exhibits an elastic-like behavior along at least one axis when subjected to an applied and subsequently released elongation. The web material includes a strainable network having at least two visually distinct regions of the same material composition. The first region undergoes a molecular-level deformation and the second region initially undergoes a substantially geometric deformation when the web material is subjected to an applied elongation in a direction substantially parallel to the axis of elongation.
691 citations
TL;DR: In this article, the response of hexagonal, metallic honeycomb to in-plane compressive loading is studied through a combination of experiment and analysis, and the local response of the material, obtained from a compression test on a representative microsection, can be used to establish the elastic properties, the load at the onset of instability and the stress level at which deformation propagates from row to row.
Abstract: The response of hexagonal, metallic honeycomb to in-plane compressive loading is studied through a combination of experiment and analysis. This material with periodic microstructure has a load-displacement response characterized by a relatively sharp initial rise to a load maximum followed by an extended load plateau which is terminated by a sharp rise in load. In the first part of the response, the material deforms essentially in a uniform fashion (stable). Following the load maximum, deformation tends to localize to one row of cells which collapses at a dropping overall load until the walls of each cell come into contact. Contact arrests further deformation in the collapsed row of cells and causes spreading of deformation in the adjacent rows. Under displacement-controlled loading, this row by row collapse can continue, with relatively small changes in the required load, until the whole specimen is collapsed. The load required for further crushing increases sharply beyond this point. This process has been reproduced through large-scale numerical simulations of the problem. In addition, we show how the local response of the material, obtained from a compression test on a representative microsection, can be used to establish the elastic properties, the load at the onset of instability, and the stress level at which deformation propagates from row to row. The local response is subsequently used to study the problem parametrically.
433 citations
TL;DR: In this paper, the microstructure of deformation bands with little or no cataclasis, with cataclastic deformation, and with clay smearing was studied at Arches National Park.
346 citations
01 Jan 1994
TL;DR: In this paper, the principles of sediment deformation are discussed. But they do not consider the effect of deformation structures preserved in rocks, and they focus on the deformation structure preservation.
Abstract: Introduction and overview. Mechanical principles of sediment deformation. Glacial deformation. Sedimentary deformational structures. Mass movements. Tectonic deformation - stress paths and strain histories. Fluids in deforming sediments. Melanges - illustrations of the dewatering, deformation, diagenesis interplay. Deformation structures preserved in rocks. Chief mathematical symbols used. References. Index.
329 citations
TL;DR: Distributed irreversible deformation in otherwise brittle ceramics has been observed in Hertzian contacts in silicon carbide and micaceous glass-ceramic, and an important manifestation is an effective "ductility" in the indentation stress-strain response.
Abstract: Distributed irreversible deformation in otherwise brittle ceramics (specifically, in silicon carbide and micaceous glass-ceramic) has been observed in Hertzian contacts. The deformation takes the form of an expanding microcrack damage zone below the contact circle, in place of the usual single propagating macrocrack (the Hertzian "cone fracture") outside. An important manifestation of this deformation is an effective "ductility" in the indentation stress-strain response. Control of the associated brittle-ductile transition is readily effected by appropriate design of weak interfaces, large and elongate grains, and high internal stresses in the ceramic microstructure.
312 citations
TL;DR: Deep-seated gravitational slope deformations and their relationships with tectonic deformation of rocks are considered, to examine the viewpoint of Tectonics as a causative factor in slope deformation as discussed by the authors.
201 citations
Journal Article•
TL;DR: Partitioning transpressional and transtensional displacement fields into pure shear-enhanced trans-pressional/transtional domains separated by narrower strike-slip shear zones or faults can be modeled in the kinematic framework presented in this article.
Abstract: of lines and planes can be calculated. These quantities are reftected in the fabrics of deformed rocks ( orientation and intensity of lineations, foliations, etc.) which can be used to qualitatively or quantitatively describe the deformation of both active and ancient transpressional/ transtensional deformation zones. Partitioning of transpressionalj transtensional displacement fields into pure shear-enhanced transpressional/ transtensional domains separated by narrower strike-slip shear zones or faults can be modeled in the kinematic framework presented here, and may be applied to centimeter scale partitioning as well as to partitioning at the scale of plate boundary deformation zones.
189 citations
181 citations
TL;DR: An interactive deformation technique called AxDf (Axial Deformations), which allows deformations, such as bending, scaling, twisting and stretching, that can be controlled with a 3D axis to be easily specified.
Abstract: The paper is part of a research effort that focuses on the provision of more efficient and effective design methods for broadcast modelling systems. It presents an interactive deformation technique called AxDf (Axial Deformations). Based on the paradigm of the modelling tool, the axial-deformations technique allows deformations, such as bending, scaling, twisting and stretching, that can be controlled with a 3D axis to be easily specified. Moreover, AxDf can easily be combined with other existing deformation techniques.
150 citations
TL;DR: In this article, the Sveconorwegian Frontal Deformation Zone (SFDZ) is proposed as a more appropriate alternative in southern Sweden (south of lake Vattern) and correspond to a younger set of oblique ductile deformation zones with reverse and right-lateral components of movement in the easternmost part of the orogen farther to the north.
TL;DR: In this article, the elastoplastic asperity-based model for the contact of rough surfaces is presented and compared with results obtained from other models, as well as with experimental results.
TL;DR: The high tensile loads required for failure were consistent with clinical and biomechanical studies and indicated the importance of the aponeurosis in foot function and arch stability.
Abstract: Material properties of the plantar aponeurosis were determined by a two-dimensional video tracking method to simultaneously measure the aponeurosis deformation. Failure loads averaged 1189 ± 244 N ...
01 Jan 1994
TL;DR: In this article, an analllyses of the elastoplastic deformation in a layered bimaterial with a sharp interface which is subjected to cyclic variations in temperature are derived, as functions of the thermomechanical properties and the geometry of the layers.
Abstract: We present analllyses of the elastoplastic deformation in a layered bimaterial with a sharp interface which is subjected to cyclic variations in temperature. Closed-form solutions are derived, as functions of the thermomechanical properties and the geometry of the layers, for different critical temperatures at which distinct transitions occur in the deformation due to thermal fluctuations. Finite-element simulations are also used to examine the stress-strain hysteresis and the evolution of monotonic and cyclic plastic zones along interfaces and sharp edges in the layered material during thermal cycling. The influence of variations in physical and mechanical properties of the constituent phases with temperature on thermally-induced deformation is investigated. Analytical results arc also compared with the predictions of the finite-element models for a layered Ni-A12O3 model bimaterial system. Furthermore, the analytical predictions are found to be in good agreement with experimental measurements of curvature during thermal cycling of a layered material comprising an Al film on a Si substrate.
Book•
01 Jan 1994
TL;DR: In this article, the authors propose a model for elastic-inelastic deformation based on elasticity and creep, and a fraction of models for increasing complexity large strain plasticity.
Abstract: Preliminaries Mechanisms of plasticity and creep Thermodynamics of Elastic-inelastic Deformation Elementary models of small Deformations Computational aspects Fraction models for increasing complexity Large strain plasticity
TL;DR: In this paper, the authors study the dependence of deformation on the assumed constitutive model of a given microstructure and the subsequent invcstigation of their localization and stability behavior under finite strains.
Abstract: SOLIDS THAT I:XHIUIT localization of deformation (in the form of shear bands) at sufficiently high levels of strain, are ftrcquently modeled by gradient type non-local constitutive laws. i.e. continuum theories that include higher order deformation gradients. These models incorporate a length scale for the localized deformation zone and are either postulated or justified from micromechanical considerations. Of interest here is the consistent derivation of such models from a given microstructure and the subsequent invcstigation of their localization and stability behavior under finite strains. In the interest of simplicity. the microscopic model is a discrete, periodic, non-linear elastic lattice structure in two or three dimensions. The corresponding macroscopic model is a continuum constitutivc law involving displacement gradients of all orders. Attention is focused on the simplest such model. namely the one whose energy density includes gradients of the displacements only up to the second order. The relation between the ellipticity of the resulting first (local) and second (non-local) order gradient models at finite strains, the stability of uniform strain solutions and the possibility of localized deformation zones is discussed. The investigations of the resulting continuum are done for two different microstructures, the second one of which approximates the behavior of perfect monatomic crystals in plane strain. Localized strain solutions based on the continuum approximation are possible with the tirst microstructure but not with the scc nd. Implications for the stability of three-dimensional crystals using realistic interaction potentials are also discussed. I. INTRO~XJCTI~N A FEATURE SHARED BY MANY ductile solids when sufficiently strained, is the transition of their deformation field from a smoothly varying pattern into a highly localized deformation pattern in the form of a “slzenr hand”. This instability phenomenon is local, i.e. it appears at any point whose stresses reach a critical level, and it is modeled in continuum mechanics as a loss ofellipticity in the incremental equilibrium equations of the solid. The characteristic surfaces of the governing equations indicate the position of the localized deformation zones. This approach has been proposed in the context of elasticity by HADAMARD (1903) and subsequently for rate independent elastoplastic solids by THOMAS (196 I), HILL (I 962) and MANDEL (I 966). Numerous works have subsequently concentrated on the study of the localization of deformation’s dependence on the assumed constitutive model. For further information on this subject, the interested reader is referred to KNOWLES and STERNBERC (1977) for elastic materials and RICE (1976) for inelastic ones.
TL;DR: In this paper, experimental measurements have been made of the shell deformation during the impact of a motorcycle helmet, and the compressive stress-strain relationship of the foam liner, which is used to construct a computer model of the performance of helmets, that allow the effects of different shell materials and different foam densities to be predicted.
TL;DR: The characteristics of fracture by cavitation in superplastic materials are reviewed in this paper, with particular attention paid to the theoretical developmental aspects of cavity nucleation, cavity growth and cavity interlinkage.
Abstract: The characteristics of fracture by cavitation in superplastic materials are reviewed. Particular attention is paid to the theoretical developmental aspects of cavity nucleation, cavity growth and cavity interlinkage. Various factors, including grain boundary sliding, impurity atoms or particles, phase proportion, deformation temperature, strain rate, strain and grain size, are discussed. Finally, methods for controlling cavitation during superplastic deformation are summarized, and problems which require further work are also presented.
TL;DR: Boyer et al. as mentioned in this paper showed that the deformation of dolomite along a minor thrust fault within the Mountain City window, Tennessee, took place by twinning, fracturing, pressure solution, and recrystallization processes.
Abstract: Deformation of dolomite along a minor thrust fault within the Mountain City window, Tennessee, took place by twinning, fracturing, pressure solution, and recrystallization processes. Deformation otherwise unobservable can be seen using cathodoluminescence and doubly polished ultrathin (∼5 μm) sections. A transect across the hanging wall, starting at 14 m above and approaching the hanging-wall/footwall (hw/fw) contact, and crosscutting relationships suggest a temporal sequence of deformation: (1) Twinning occurred in the coarser fraction of grains, and material was removed along bedding parallel stylolites. (2) Dolomite recrystallized at the edges of veins. Fine-grained deformation zones composed of dynamically recrystallized dolomite formed. Transgranular hairline fractures formed, visible only under cathodoluminescence. (3) Grain size decreased. Recrystallization occurred at grain boundaries, along veins, and within fine-grained deformation zones. The proportion of twinned grains decreased with twinning only within the coarser fraction of grains. The proportion of veins and fractures increased. (4) Bedding-parallel stylolites offset deformation zones and veins, indicating reactivation. Intersection relationships indicate that stylolites, fractures, and deformation zones all acted concurrently. (5) At the hw/fw contact, the rock is finer grained and homogeneous. Very few veins or stylolites remain. The regional geology (Boyer and Elliott, 1982) suggests that deformation took place at a depth of 9 km (270 °C at a 30 °C/km geothermal gradient). Experimental data (for example, Turner and others, 1954) suggest that dolomite would not deform by dynamic recrystallization under these conditions. However, fluids may reduce the strength and increase the ductility of calcite rocks (Rutter, 1972). Similarly, fluids may have reduced the temperature at which dynamic recrystallization could take place in these dolomitic rocks. The volume of mesoscopic fractures, microscopic luminescing fractures, and the mean grain size decrease as the hw/fw contact is approached. Grain-size reduction in conjunction with the influx of fluids may have resulted in a change in the dominant deformation mechanism from fracturing to dynamic recrystallization.
TL;DR: In this paper, the surface relief of a superplasticity deformed magensium alloy (Mg-1.5% Mn-0.3%Ce) was studied by means of vacuum etching.
Abstract: The surface relief of a superplasticity deformed magensium alloy (Mg-1.5% Mn-0.3%Ce) was studied. Zones/bands of localized deformation were detected by means of vacuum etching. Between the localized deformation bands were less-deformed regions. After 20% elongation in vacuum (1.33 × 10−3 Pa), zones of intensive vacuum etching were observed as two intersecting bands of localized deformation oriented at 35–60° to the tensile axis. Spacing between the localized deformation bands is 6–8 grain diameters after a tensile elongation of 20% and 3–4 grain diameters after an elongation of 160%. The observed bands of strain localization are explained from the viewpoint of cooperative grain boundary sliding, i.e. shifting of grain groups as a whole unit along grain boundary surfaces oriented close to the maximum shear stress direction. It is suggested that the cooperative nature of GBS be taken into account when evaluating the real local strain rate and the real strain-rate sensitivity of grain boundary sliding process.
TL;DR: In this paper, a qualitative description of the effects of roll pass geometry and pressing on the performance of superconducting tapes produced by the OPIT method is presented, and the deformation process variables are analyzed in terms of the stresses and strains imposed during processing.
TL;DR: In this article, a 78-station 270 km wide Global Positioning System (GPS) network which spans the arc-continent collision zone in southern Taiwan has been surveyed 5 times from 1990 to 1994 with dual-frequency geodetic GPS receivers.
Abstract: A 78-station 270 km wide Global Positioning System (GPS) network which spans the arc-continent collision zone in southern Taiwan has been surveyed 5 times from 1990 to 1994 with dual-frequency geodetic GPS re ceivers. T he observed data are processed with Bernese software, v.3.4, using the available precise ephemerides. The unknown residual tropospheric zenith delays are estimated once per 6-8 hour session for each station in the least squares adjustment of carrier phase observations. The standard errors of GPS observed lengths are in the range of 5 to 9 mm for a baseline of 3-120 km in length.· The changes in baseline length are utilized to study the spa tial variations of crustal strain and estimate the relative velocities of geodetic stations. We found that the deformation zone caused by the active collision process is probably 200 km in width. The Coastal Plain, eastern part of the Western Foothi1ls, Central Range, and Coastal Range show slight to moder ate strain rates. Remarkable contractions of0.51-1.65 μstrain/yr in 100°-120° are detected in the vicinity of the Chukou fault. The Longitudinal Valley gives extremely high shortening rates of 3.2-6.1 μstrain/yr in 109° -133°. It is ob vious due to the aseismic slip on the Longitudinal Valley fault as previously demonstrated by trilateration data. The velocity field of GPS stations reveals a fan-shaped pattern consistent with the directions of maximum compres sional tectonic stress inferred from borehole breakout data, earthquake focal mechanisms, and Quaternary geological data. The GPS observed velocity of Lanhsu on the Luzon arc relative to Paisha, Penghu of the Chinese conti nental margin, 86.3±2.4 mm/yr in 307°±1°, is almost in the same direction as that proposed by Seno (1977) or Seno et al. (1993), but the rate is about 15-20% faster. (
TL;DR: In this paper, a powder flow model was proposed to describe the materials behavior during the deformation process of Ag-sheathed superconducting tapes, and the model showed that the final density of the core does not directly depend on the initial packing density.
TL;DR: Cryoelectron microscopy of ultrathin cyrosections permits study of the ultrastructure of cells in the hydrated state, however, cryosectioning deforms the cut volume as the sections are compressed in the cutting direction while their thickness is increased with respect to the cutting feed.
TL;DR: In this article, the authors observed adhesion-induced deformation of polystyrene particles on silicon substrates as a function of time using scanning electron microscopy and found that the deformation increases with time for a period of approximately 72 hours before reaching a constant value.
Abstract: Adhesion-induced deformations of submicrometer polystyrene particles on silicon substrates were observed as a function of time using scanning electron microscopy. The contact area between the particle and the substrate was found to increase with time for a period of approximately 72 hours before reaching a constant value. The ratio of the final contact radius to the particle radius was ~ 0.4. The time dependence of this deformation appears similar to the creep phenomenon in bulk polymers. These results are related to the studies of particle removal conducted for different time periods, using hydrodynamic and centrifugal removal forces. The removal efficiency was found to decrease with time. This correlates well with the increase in the adhesion force on the particles with time as observed from the SEM measurements. The effect of the particle diameter on the removal efficiency and the correlation between the time dependent adhesion-induced deformation and particle removal efficiency is discussed.