Stress field

About: Stress field is a research topic. Over the lifetime, 11926 publications have been published within this topic receiving 226417 citations.

KINE3D: a New 3d Restoration Method Based on a Mixed Approach Linking Geometry and Geomechanics

Abstract: We developed a new methodology for 3D restoration by coupling a geometric modelling software and a mechanical finite-element code. This method allows the geologist to impose the displacement on the main faults in order to get an adequate restored geometry and to compute the 3D strain and stress fields within the main blocks based on the unfolding with the mechanical approach. Complex meshing of the solid take into account heterogeneities due to the layering and facies variation. Results are discussed on compressive and extensional contexts, as well as in backward and forward approaches. The compressive case is illustrated by the restoration of a faulted anticline with massive sand and shaly beds. This case has been also restored with 2D surface unfolding processes and we will compare the information that geologists may get from the various methods. The second case concerns the deformation, in a gravity gliding context, of a sandy channel embedded into a shaly matrix. The mixed approach allows to quantify the reorientation of the stress field on the sand/shale boundary.

Geometric formulation of quantum stress fields

Abstract: We present a derivation of the stress field for an interacting quantum system within the framework of local-density-functional theory. The formulation is geometric in nature, and exploits the relationship between the strain tensor field and Riemannian metric tensor field. Within this formulation, we demonstrate that the stress field is unique up to a single ambiguous parameter. The ambiguity is due to the nonunique dependence of the kinetic energy on the metric tensor. To illustrate this formalism, we compute the pressure field for two phases of solid molecular hydrogen. Furthermore, we demonstrate that qualitative results obtained by interpreting the hydrogen pressure field are not influenced by the presence of the kinetic ambiguity.

Flaw Tolerance in a Thin Strip Under Tension

Abstract: Recent studies on hard and tough biological materials have led to a concept called flaw tolerance which is defined as a state of material in which pre-existing cracks do not propagate even as the material is stretched to failure near its limiting strength. In this process, the material around the crack fails not by crack propagation, but by uniform rupture at the limiting strength. At the failure point, the classical singular stress field is replaced by a uniform stress distribution with no stress concentration near the crack tip. This concept provide an important analogy between the known phenomena and concepts in fracture mechanics, such as notch insensitivity, fracture size effects and large scale yielding or bridging, and new studies on failure mechanisms in nanostructures and biological systems. In this paper, we discuss the essential concept for the model problem of an interior center crack and two symmetric edge cracks in a thin strip under tension. A simple analysis based on the Griffith model and the Dugdale-Barenblatt model is used to show that flaw tolerance is achieved when the dimensionless number A n =ΓE/(S 2 H) is on the order of 1, where r is the fracture energy, E is the Young s modulus, S is the strength, and H is the characteristic size of the material. The concept of flaw tolerance emphasizes the capability of a material to tolerate cracklike flaws of all sizes.

Stress evolution in southern California and triggering of moderate-, small-, and micro-size earthquakes

Abstract: We calculate the evolution of stresses in southern California, extending the study of Deng and Sykes [1997] by increasing from 6 to 36 the number of earthquakes for which coseismic changes in stress are computed and by expanding from M≥6 to M≥1.8 the range of magnitudes M of events whose focal mechanism solutions are examined in the context of the evolving stress field. The cumulative stress on a given date is calculated with respect to an arbitrary zero baseline just before the 1812 Wrightwood earthquake. By taking into account the long-term stress loading associated with 98 fault segments and coseismic stress changes for 36 significant earthquakes, our calculations indicate that more than 85% of M≥5 earthquakes from 1932–1995 occurred in regions of positive change in Coulomb failure function (ΔCFF). Most of the remaining about 15% earthquakes that occurred in areas of negative ΔCFF fall very close to boundaries between positive and negative ΔCFF, some of which are sensitive to the less well controlled slip distributions of the earliest historic events. Calculations also show that from 1981 until just before the 1992 Landers earthquake more than 85% of small- (M≥3) and micro-size (M≥1.8) shocks in the Seeber and Armbruster [1995] catalog with mechanisms involving either NW trending right-lateral or NE trending left-lateral strike-slip faulting occurred in regions of positive ΔCFF. The ratio of encouraged to all small- and micro-size events reaches a high value of about 88% if an apparent coefficient of friction μ between 0.0 and 0.6 is used. The highest percentage of earthquakes occurred in areas where stress is about 1 MPa above the 1812 baseline. Most (66%) events occurred in regions of ΔCFF between 0.0 and 2.0 MPa. The upper limit indicates that the approximate range of stress variation in the earthquake cycle is of the order of 2.0 MPa. The fact that the locations of most moderate-, small-, and micro-size earthquakes are still related to stress changes remaining from large historical events might be used to constrain slip distribution of some of those earthquakes and to constrain the locations of future significant events.