The deformation of the ground around surface faults

1961 ◽  
Vol 51 (3) ◽  
pp. 355-372 ◽  
Author(s):  
M. A. Chinnery

Abstract A rectangular dislocation surface (i.e., a surface across which there is a discontinuity in the displacement vector) is used as a model of a vertical transcurrent fault. The results of Steketee (1958a) are employed to derive, in analytical form, the displacement field throughout a semi-infinite elastic medium due to such a dislocation. In particular, the displacements of the surface of the medium are calculated in some detail, and contour maps of the various components are given for two representative cases. The solution to the limiting case of a fault of infinite length is also included. Methods are then discussed for the determination of the depth of a surface fault from measurements of the deformation of the ground produced by it, and these are applied to the faults associated with the Tango and North Idu earthquakes, and to the San Andreas fault. In each of these cases, the general features of the crustal deformations agree well with the predictions of the theory, and it is concluded that dislocation theory provides a good description of the effects of fracture in the earth's crust.

Author(s):  
Мария Михайловна Вислогузова ◽  
Дмитрий Викторович Гоцев ◽  
Алексей Викторович Ковалев ◽  
Александр Иванович Шашкин

Как известно при нагревании твердые тела, в частности металлы, испытывают температурные деформации, связанные с эффектом линейного расширения. При этом, несмотря на то, что эти деформации малы, соответствующие им напряжения могут оказаться достаточно большими, зачастую превосходящими предел текучести материала. В связи с этим для описания напряженно-деформированных состояний тел, находящихся под действием высоких температур, необходимо учитывать неупругое поведение материалов. Определению напряжений и деформаций в упругопластических задачах посвящено множество работ, в том числе исследования [1-10]. В некоторых из них [1], [5-10] рассматривается температурное воздействие на тела различной конфигурации. В настоящей работе решается задача об определении осесимметричного поля напряжений в плоском диске при воздействии на него точечного источника тепла (например, точечная сварка). Материал диска моделируется упрочняющейся упругопластической средой. Задача решалась в рамках плоско-напряженного состояния методом малых возмущений. В аналитическом виде получены соотношения, описывающие распределение полей напряжений в упругой и пластической областях деформирования. В качестве условий сопряжения решений на упругопластической границе использовались условия неразрывности радиальной и окружной компонент тензора напряжений и радиальной компоненты вектора перемещений. As you know, when heated, solids, in particular metals, experience thermal deformations associated with the effect of linear expansion. Moreover, in spite of the fact that these strains are small, the corresponding stresses can be quite large, often exceeding the yield stress of the material. In this regard, to describe the stress-strain states of bodies exposed to high temperatures, it is necessary to take into account the inelastic behavior of materials. Determination of stresses and strains in elastoplastic problems has been the subject of many works, including studies [1-10]. Some of them [1], [5-10] consider the temperature effect on bodies of various configurations. In this work, we solve the problem of determining the axisymmetric stress field in a flat disk when exposed to a point heat source (for example, spot welding). The disc material is modeled by a hardening elastoplastic medium. The problem was solved within the plane-stressed state by the method of small perturbations. In an analytical form, relations are obtained that describe the distribution of stress fields in elastic and plastic deformation regions. The conditions of continuity of the radial and circumferential components of the stress tensor and the radial component of the displacement vector were used as conditions for conjugation of solutions on the elastoplastic boundary.


Author(s):  
D. Goyal ◽  
A. H. King

TEM images of cracks have been found to give rise to a moiré fringe type of contrast. It is apparent that the moire fringe contrast is observed because of the presence of a fault in a perfect crystal, and is characteristic of the fault geometry and the diffracting conditions in the TEM. Various studies have reported that the moire fringe contrast observed due to the presence of a crack in an otherwise perfect crystal is distinctive of the mode of crack. This paper describes a technique to study the geometry and mode of the cracks by comparing the images they produce in the TEM because of the effect that their displacement fields have on the diffraction of electrons by the crystal (containing a crack) with the corresponding theoretical images. In order to formulate a means of matching experimental images with theoretical ones, displacement fields of dislocations present (if any) in the vicinity of the crack are not considered, only the effect of the displacement field of the crack is considered.The theoretical images are obtained using a computer program based on the two beam approximation of the dynamical theory of diffraction contrast for an imperfect crystal. The procedures for the determination of the various parameters involved in these computations have been well documented. There are three basic modes of crack. Preliminary studies were carried out considering the simplest form of crack geometries, i. e., mode I, II, III and the mixed modes, with orthogonal crack geometries. It was found that the contrast obtained from each mode is very distinct. The effect of variation of operating conditions such as diffracting vector (), the deviation parameter (ω), the electron beam direction () and the displacement vector were studied. It has been found that any small change in the above parameters can result in a drastic change in the contrast. The most important parameter for the matching of the theoretical and the experimental images was found to be the determination of the geometry of the crack under consideration. In order to be able to simulate the crack image shown in Figure 1, the crack geometry was modified from a orthogonal geometry to one with a crack tip inclined to the original crack front. The variation in the crack tip direction resulted in the variation of the displacement vector also. Figure 1 is a cross-sectional micrograph of a silicon wafer with a chromium film on top, showing a crack in the silicon.


1993 ◽  
Author(s):  
Sandra S. Schulz ◽  
Robert E. Wallace

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