Showing papers on "Deformation (meteorology) published in 1976"
12 Oct 1976-Philosophical transactions - Royal Society. Mathematical, physical and engineering sciences
TL;DR: In this paper, a simple model for rock deformation by pressure solution, assuming grain boundary diffusive mass transfer to be deformation rate controlling, is presented, which leads to a constitutive flow law which is of the same form as that for Coble creep.
Abstract: A simple model for rock deformation by pressure solution, assuming grain boundary diffusive mass transfer to be deformation rate controlling, is presented. The model leads to a constitutive flow law which is of the same form as that for Coble creep. It is argued that the presence of a fluid film in stressed grain boundaries leads to enhanced diffusivity of solute particles in the grain boundary. Some simple experiments are described, which demonstrate rapid diffusion in solutions in pores, much slower diffusion in stressed interfaces and deformation by pressure solution. By using the theoretical model, and by assuming that the pressure of the interfacial solution is equal to the applied normal stress, so that available experimental data on the effect of pressure on mineral solubility could be used, rates of deformation by pressure solution have been calculated. These are compared with rates of deformation by crystal plastic and high temperature diffusive flow processes, by using deformation mechanism maps. Predicted transition conditions between various deformation mechanisms are found to be consistent with those inferred from the study of textures of naturally deformed rocks.
677 citations
TL;DR: In this article, the success of this separation can be tested by comparison of the vibration ellipsoids of bonded atom pairs, which should have equal amplitudes in the bond direction.
Abstract: The frequent practice of combining X-ray and neutron diffraction for distinguishing vibrational smearing from charge deformation due to chemical bonding is neither necessary nor completely satisfactory. The two effects occur principally in distinct regions of real and reciprocal space. They can be distinguished by X-ray data alone provided these extend to reciprocal radii d* > 2 A- 1 and provided the refinement program allows explicitly for the bonding deformation. The success of this separation can be tested by comparison of the vibration ellipsoids of bonded atom pairs, which should have equal amplitudes in the bond direction. Application of this 'rigid-bond' test to four recent refinements using the charge deformation model shows the vibration parameters to be largely unbiased, as those from parallel spherical-atom refinements are not. Hydrogen vibration parameters cannot be derived from X-ray data because of large deformation densities at the nuclei; nor do they satisfy the rigid-bond postulate.
675 citations
627 citations
Book•
01 Aug 1976
526 citations
422 citations
287 citations
TL;DR: In this article, volume change constitutive relations for unsaturated soils are proposed from a semi-empirical standpoint, where one equation describes the deformation of the soil structure and a second equation defines...
Abstract: Volume change constitutive relations for unsaturated soils are proposed from a semi-empirical standpoint. One equation describes the deformation of the soil structure and a second equation defines ...
272 citations
TL;DR: The formation and properties of machining burrs were studied by LaRoux K. Gillespie as mentioned in this paper, who found that the format ion of burrs in machining operations occurs by three basic Mechanisms: I) lateral extrusion of material 2) bending of a chip 3) tearing of the chip from the workpit.
Abstract: The Formation and Properties of Machining Burrs by LaRoux K. Gillespie, Master of Sd,.nce Utah Stale University, 1973 Majo r P r ofessor: Dr . Carl D. Spear Department: Manufacturing Engineering xii i The format ion of burrs in Machining Operations occurs by three Basic Mechanisms: I) Lateral extrusion of material 2) B<'nding of th<> chip 3) Tearing of the chip from the workpit>ce Each of these mechanisms has be en studied analytically and compared to expE>rimental results. The ag reE>ment between predictions and measurempnts has been found to be close. Drilling , milling, grinding, and turning burrs w<>re producpd in 303Se stain]pss steel and their properties were related to tool geomelry. feedrat es . and depth of cut . One thousand measurements were made and subs.-que ntly analyzed by analysis of variance techniques. The p r operties measured include burr length and thickness.
238 citations
01 Jan 1976
213 citations
Abstract: The author reviews characteristic features of the effect of simultaneous moisture change and load on the deformation of wood and discusses their implications for any model based on the botanical and molecular structure of wood.
153 citations
TL;DR: In this paper, the volume changes accompanying the deformation of rubber-like solids are analyzed on the basis of isotropic elasticity theory and a simple, but general, result relating the volume and the stretch in simple tension is obtained.
Abstract: V olume changes accompanying the deformation of rubber-like solids are analysed on the basis of isotropic elasticity theory. In particular, a simple, but general, result relating the volume and the stretch in simple tension is obtained. This is achieved by the introduction of certain modified principal stretches which allow the dependence of the strain energy on the isochoric and the dilatational parts of the deformation to be considered separately. The fact that volume changes in rubber-like solids are typically of order 0.01 % is used to linearize the stress-deformation relations in the dilatation. This enables the dilatation to be given explicitly as a function of the stretch in simple tension. Specific results are obtained for certain classes of constitutive law and good agreement with the experimental data for simple tension is demonstrated. Results for equi-biaxial tension and pure shear are also given in anticipation of further experimental data becoming available. The need for volume-change data for a wide variety of types of strains is emphasized.
TL;DR: In this paper, a finite theory of the elastoviscoplastic behavior of single crystals based on the theoretical and experimental results concerning the microdynamics of crystal defects is presented.
TL;DR: A new compact sizing instrument, "Metricell," equipped with a particle-independent electrical calibrating system, is described, and the absolute volume evaluation of particles has been studied with model particles in enlarged model orifices of different lengths.
Abstract: To understand the basic events during the passage of particles through the Coulter orifice, three experiments were performed. (1) The denpendence of the volume results on the particle path has been shown by ink-colored particle beams. (2) The deformation and alignment of cells during their passage through the orifice have been photographed by a nano-second photographing technique. (3) The absolute volume evaluation of particles has been studied with model particles in enlarged model orifices of different lengths. A new compact sizing instrument, "Metricell," equipped with a particle-independent electrical calibrating system, is described.
TL;DR: In this paper, sufficient experimental results are available for the construction of deformation maps for two superplastic materials, Zn-22% Al and Pb-62% Sn, and when plotted in the form of grain size versus stress, the maps for these two alloys provide strong evidence that super-plasticity only occurs at grain sizes sufficiently small that a stable subgrain structure is not formed during deformation.
TL;DR: In this article, a simplified reversible non-hydrostatic crystal-solution thermodynamic criterion based on Gibbs provides a manageable basis for determining the direction in which the process will run (regions of dissolution or growth) in stressed porous, non-porous, closed and open systems.
Abstract: Pressure-solution and associated crystallization are subclasses of a diffusive mass transport process which involves diffusion in grain boundary and pore solutions. The manner in which they give rise to permanent deformation is examined in three steps: (a) A simplified reversible non-hydrostatic crystal-solution thermodynamic criterion (first order, 2-components) based on Gibbs provides a manageable basis for determining the direction in which the process will run (regions of dissolution or growth) in stressed porous, non-porous, closed and open systems. (b) Considerations of irreversible diffusion and deformation indicate certain restrictions on the displacements accompanying permanent growth or dissolution and hence on the form of the solution-transfer strain rate tensor. (c) The way in which the process develops, and its rate, are governed by kinetic factors, especially diffusion kinetics. As well as having an exponential dependence on stress, the displacement rate is influenced by absolute temperature, grain boundary diffusivity, initial solubility and geometric scale.
TL;DR: In this paper, the grain-boundary sliding during superplastic flow of the Pb-Sn eutectic was observed and a threshold stress of 1.3×106N m−2 was observed for the onset of super-plastic deformation.
Abstract: Dynamic observations of grain-boundary sliding during superplastic flow of the Pb-Sn eutectic are reported. These observations confirm the postulate that the dominant deformation mode during superplastic flow is grain-boundary sliding with localized deformation necessary to maintain grain coherency. Extensive grain-boundary sliding is also observed when the strain-rate and/or grain size is outside the superplastic flow regime. Stress relaxation tests were also carried out on the Pb-Sn eutectic. These tests provide data on the activation energy (45±5 kJ mol−1), grain-size dependence (d−3), and stress dependence of superplastic flow in this alloy. A threshold stress of 1.3×106N m−2 for the onset of superplastic deformation is also observed.
TL;DR: The magnetic anisotropy of a sequence of rocks ranging from shales and greywackes to gneisses was investigated in this article, where the oblate and slightly eccentric magnetic susceptibility ellipsoids in sediments were progressively changed when sediments are subject to metamorphism and ductile deformation.
TL;DR: In this paper, the effect of the pulsed current increases with increasing current frequency and pulse duration, which is explained by the variation in the rate of electron-dislocation interaction during microstress reversal due to an electron cloud in the deforming crystals.
Abstract: Conclusions1.The plastic deformation of metal, which is stimulated by current pulses, consists of a true electroplastic deformation, which is only slightly associated with the thermal effect of the current and a deformation dependent on the pinch effect of the current. The effect of the pulsed current increases with increasing current frequency and pulse duration.2.A change in the direction of the current in crystals subject to deformation gives rise to variation in their resistance to deformations; this is demonstrated in a variation of the specimen's stress-relaxation and creep rates. This is explained by the variation in the rate of electron-dislocation interaction during microstress reversal due to an electron cloud in the deforming crystals. Considering the dependence of the thermal and pinch effects of the current on its direction in specimens, the result obtained is reliable evidence supporting the presence of a metal's true electroplasticity.
20 Feb 1976
TL;DR: In this paper, a traverse through steeply inclined rocks north-west from Birnam is the equivalent of a vertical section at one point through the Tay Nappe, and it suggests that the second episode of deformation at a low level was largely responsible for the emplacement of the nappe by simple shear.
Abstract: Synopsis A traverse through steeply inclined rocks north-west from Birnam is the equivalent of a vertical section at one point through the Tay Nappe. This traverse demonstrates increasing complexity and intensity of deformation at successively lower structural levels in the nappe. It suggests that the second episode of deformation (D2) at a low level was largely responsible for the emplacement of the nappe by simple shear, and that displacements of the order of 6 km during this episode can be demonstrated in the limited thickness of rocks exposed in the district. The earliest deformation (D1) induced two cleavages in the Southern Highland (Upper) Dalradian sandstones—one analogous to slaty cleavage and the other a tectonic striping produced by pressure solution. One set of folds, now downward-facing following D4 downbending, is associated with these cleavages. D2 deformation strongly modified the limbs and ‘facing’ characteristics of the D1 folds.
TL;DR: In this paper, the symmetry of the deformation texture and the size of the fundamental area are related to the properties of the displacement gradient which describes the strain, and a new classification of cold deformation textures has become possible.
TL;DR: In this paper, the influence of the geometrical parameters on the modes of deformation of the tubes is discussed in general terms, and the surface stresses are examined by means of the brittle laquer technique and strain gauges.
TL;DR: In this article, a finite theory of the elastoviscoplastic behavior of single crystals based on the theoretical and experimental results concerning the microdynamics of crystal defects is presented.