Showing papers on "Deformation (meteorology) published in 1972"

Deformation of the Earth by surface loads

Abstract: The static deformation of an elastic half-space by surface pressure is reviewed. A brief mention is made of methods for solving the problem when the medium is plane stratified, but the major emphasis is on the solution for spherical, radially stratified, gravitating earth models. Love-number calculations are outlined, and from the Love numbers, Green's functions are formed for the surface mass-load boundary-value problem. Tables of mass-load Green's functions, computed for realistic earth models, are given, so that the displacements, tilts, accelerations, and strains at the earth's surface caused by any static load can be found by evaluating a convolution integral over the loaded region.

Atmospheric Frontogenesis Models: Mathematical Formulation and Solution

Abstract: The approximation of geostrophic balance across a front is studied. Making this approximation, an analytic approach is made to a frontogenesis model based on the classic horizontal deformation field. Kelvin's circulation theorem suggests the introduction of a new independent variable in the cross-front direction. The problem is solved exactly for a Boussinesq, uniform potential vorticity fluid. Non-Boussinesq, non-uniform potential vorticity, latent heat, and surface friction effects are all studied. Using a two-region fluid we model the effects of confluence near the tropopause. A similar approach is made to the appearance of fronts in the finite-amplitude development of the simplest Eady wave; this is also solved analytically. Based on the surface fronts produced by these models, we give a general model of a strong surface front. There is a tendency to form discontinuities in a finite time.

Deformation of Nematic Liquid Crystals in an Electric Field

Abstract: The problem of a nematic liquid crystal in an electric field is solved. Effects due to conductivity of the liquid have been neglected. Numerical solutions are given for various values of parameters. The solution is compared with experimental data taken from the literature. A computer program has been developed to do a non-linear least-squares fit of experimental data with the solution given in the present paper.

Deformation Paths in Structural Geology

Abstract: The evolution of folds and the origin of mineral orientations and schistosity are analytically related to the deformation paths or histories in deforming rocks. The several different finite and incremental methods of representing deformation paths are connected by matrix algebra, and graphical presentation in natural strain space is found to be particularly clear. New methods permit calculation of various components of deformation paths from boudinage, pressure shadows, and inclusion trails in naturally deformed metamorphic rocks. In coaxially accumulating deformation paths the principal strains remain parallel to the same material lines in the rock and have been referred to inappropriately as irrotational. Straight inclusion trails in metamorphic minerals may be produced by synkinematic grain growth during a coaxially accumulating path and do not necessarily indicate postkinematic grain growth. Synkinematic inclusion trails can be produced by growth of the grain through its pressure shadow rather than matrix schistosity, and the quartz protected from re-crystallization by being included in snowball garnets may sometimes form this way.

Electron microscope investigation of the microplastic deformation mechanisms of silicon by indentation

Abstract: The specific features of the dislocation structure, occuring in the vicinity of indentations have been studied using Si single crystals under different conditions of deformation (at temperatures of 20 to 700 °C and loadings of 0.5 to 10 p). It is shown, that the deformation of crystals at temperatures of 350 to 650 °C results in twin formation with {111} twinning plane. Flat defects with {115} habit plane are revealed. They are shown to be platelets of a new phase, which is of the hexagonal structure with c = 6.31 A and a = 3.86 A. The possible mechanism of the phase transformation is discussed. [Russian text ignored].

The deformation mechanisms of superplasticity

Abstract: Under various conditions of stress and temperature various deformation mechanisms could be rate-controlling for superplastic deformation. In general at low stresses diffusion creep should be rate-controlling. At temperatures between approximately 40 and 65 pct of the absolute melting point grain boundary diffusion should be the dominant diffusion path while at higher temperatures volume diffusion should dominate. At intermediate stresses, grain boundary sliding should be the major deformation mode, but the sliding rate should be governed by the lesser rate of dislocation creep within the grains. At temperatures between 40 and 65 pct of the melting point, the rate of dislocation creep should be controlled by dislocation pipe diffusion, while at higher temperatures volume diffusion should be ratecontrolling. At high stresses the superplastic effect of unusually large tensile extensibility should diminish due to the greater possibility of work-hardening processes such as dislocation cell, tangle, and pile-up formation.

Theoretical meaning and observed values of deformation parameters for soil

Abstract: In a taphole gun for use in closing tapholes in blast furnaces and the like, a tamping piston is axially displaceable through a cylinder for forcing tamping material into the taphole. An annular recess is formed in the circumferential periphery of the tamping piston and a piston ring is fitted into the annular recess. The piston ring is dimensioned relative to the recess so that tamping material enters the recess and exerts pressure on the piston ring forcing it radially outwardly against the inner surface of the cylinder and axially against the tamping piston.

Design of conventional rail track foundations.

Abstract: Measurements of the distribution of vertical stress in the subgrade for given depths of ballast, track structural configurations and loading conditions are described. The mean maximum vertical stress in the subgrade can be predicted with reasonable accuracy by simple elastic theory. The results of laboratory work in which samples of soil were subjected to repeated triaxial loading are presented. For the cohesive soils tested a level of stress was found above which repeated applications of load caused large permanent deformations and below which permanent deformations were small and terminating. Based on these findings a method of track foundation design is developed in which the depth of ballast required to prevent excessive deformation of the subgrade can be predicted from the results of a simple laboratory repeated load test and a knowledge of the traffic loading to be carried. Small decreases in construction depth from the design depth produce large increases in deformation rate while large increases in construction depth over the design depth produce little return in terms of reduced rates of deformation. The proposed design procedure produces construction depths that are apparently close to the optimum for the fine grained soils so far investigated.

Deformation and Flow

Abstract: Advanced Rheology.By Markus Reiner. Pp. xiv + 374. (H. K. Lewis: London, 1971.) £8.

Tensile properties of metastable stainless steels

Abstract: Tensile properties of two similar stainless steels, types 301 and 304, were investigated for different strain-rates, grain sizes and testing temperatures, and the bulk concentration of martensite formed during deformation was determined by X-ray diffraction.

Vehicle seat comprising three foam layers

Abstract: A vehicle seat comprises three layers of polymer foams, the upper and lower layers being polyurethane and the center layer being polyethylene. The thicknesses and deformation characteristics of the layers of foam are optimized for a given overall seat thickness range so as to interact with an injury model correlating the deformation characteristics of the human spine such that deformation and hence injury to the spine, occasioned by the impacting of the rider''s upper torso upon the seat, will be minimized. A procedure of evaluating a seat in order that the deformation characteristics of the seat may be optimized is set forth.

The Nature of Deformation Lamellae in Silicates

Abstract: High voltage electron petrography of olivine crystals from a peridotite deformed experimentally at high temperature and confining pressure shows that the deformation lamellae visible optically in petrographic thin sections consist of narrow zones of closely spaced edge dislocations. The peridotite specimen was deformed in the regime where pencil glide parallel to [100] dominates flow in olivine, and areas selected from the petrographic section were thinned to electron transparency by low-angle ion bombardment. Planar arrays of parallel edge dislocations with Burgers' vector [100] on the planes normal to [010] and [011] were found. These arrays appear identical in all important respects to slip bands in metals and to the dislocation model for photoelastic deformation lamellae proposed originally to explain such features in quartz.

The Role of Grain Boundaries in Creep Deformation

Abstract: Grain boundaries of polycrystalline copper deformed under creep conditions have been studied in a 1000 kV electron microscope. Twin boundaries show dense dislocation arrangements, while high-angle boundaries are almost dislocation-free. Cavities are observed in the very early stages of formation. They are always found associated with obstacles in the grain boundaries such as triple points and kinks. These results are discussed in terms of a previously proposed model for grain-boundary sliding. The implications for the deformation of a polycrystalline material at various temperatures are also considered.

An Approach to the Problem of Progressive Failure

Abstract: In this paper, the different factors that contribute to progressive failure are briefly reviewed, and the necessary conditions for its occurrence delineated.Experiments on specimens trimmed from block samples of several clays were performed to study the post-peak stress deformation behavior. It is shown that the stiffness of the testing system has an important influence on the post-peak characteristics. A method of obtaining the effective 'residual' angle of friction from drained triaxial tests is developed.Because of the localization of deformation in the failure zone, both in the laboratory and in the field, the laboratory nominal post-peak stress–strain relationship cannot be directly applied to field problems. Based on laboratory and field observations on the mechanism of deformation, the ratio of the shear modulus of the failure zone to that of the pre-peak range is proposed as a deformation parameter to be used in analysis of progressive failure.A simplified theory for the solution of the problem of...

Interlocking device for automobile doors

Abstract: This invention provides improved collision-resisting structure for withstanding side impacts on automobile doors. The door and the door sill have interengageable elements which become coupled together upon initial deformation of the door when subjected to a side impact, preventing upward and inward deformation of the door panel by effectively locking the bottom edge of the door to the sill.

Deformation Characteristics of Granular Materials Under Hydrostatic Compression

Abstract: The deformation characteristics of sand and other granular materials under hydrostatic compression are studied in the conventional triaxial apparatus using 4 × 4 in. (10 × 10 cm) specimens. Modifications have been made for measuring small axial strains and free end platens were used. The errors in testing have been estimated and their effect was evaluated. Different kinds of granular materials were tested to study the effect of the physical properties of the material on its deformational behavior.The results showed that the total deformation of a mass of sand subjected to a hydrostatic compression is generally not recoverable, and can be divided into elastic (recoverable) and sliding (irrecoverable) components. It has also been found out that for a dense specimen of sand most of the total deformation is recoverable, since the sliding component of deformation represents only a small fraction of the total deformation. The results also showed that for the very dense specimen axial and radial strains were nea...