Stress field

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

Ensemble averaging stress–strain fields in polycrystalline aggregates with a constrained surface microstructure – Part 1: anisotropic elastic behaviour

Abstract: The effect of three-dimensional (3D) grain morphology on the deformation at a free surface in polycrystalline aggregates is investigated by means of a large-scale finite element and statistical approach. For a given two-dimensional surface at z = 0 containing 39 grains with given crystal orientations, 17 random 3D polycrystalline aggregates are constructed having different 3D grain shapes and orientations except at z = 0, based on an original 3D image analysis procedure. They are subjected to overall tensile loading conditions. The resulting stress–strain fields at the free surface z = 0 are analyzed. Ensemble average and variance maps of the stress field at the observed surface are computed. In the case of an anisotropic elastic behaviour of the grains, fluctuations ranging between 5% and 60% are found in the equivalent stress level at a given material point of the observed surface from one realization of the microstructure to another. These results have important implications in the way of comparing fin...

Mechanics of Second Order Faults and Tension Gashes

Abstract: The origin of en echelon second order shear fractures and tension gashes associated with first order, or primary, faults is examined analytically and experimentally. It is postulated that en echelon second order structures form under the influence of a stress mechanism similar to the one occurring in the direct shear test. The direct shear or modified direct shear state of stress could develop at certain points along a forming primary fault as a result of a local reduction in the normal stress acting on planes perpendicular to the displacement direction. It is argued that in most en echelon arrays the orientation of the individual fractures reflects the existence of a local state of stress, and cannot directly be correlated with the regional (primary) stress field. The zone in which they occur, however, may represent planes of high effective shear stress within the regional framework. The direct shear model (full relief of transverse normal stress) offers a stress mechanism which can explain the origin of not only en echelon tension gashes but also second order faults. For a given set of strength parameters, the type of en echelon fractures that will develop depends on the normal stress acting in the primary fault plane. In general, tension fractures form at low normal stress, shear fractures at intermediate values of normal stress, and at high normal stress a crush or shear zone is produced. If the state of stress is one of modified direct shear (only partial relief of transverse normal stress), the development of second order faults is favored.

The structure of the near-tip field during transient elastodynamic crack growth

Abstract: T he process of dynamic crack growth in a nominally elastic malerial under conditions of plane strain or plane stress is considered. Of particular concern is the influence of the transient nature of the process on the stress field in the immediate vicinity of the crack tip during nonsteady growth. Asymptotically, the crack tip stress field is square root singular at the crack tip, with the angular variation of the singular field depending weakly on the instantaneous crack tip speed and with the instantaneous stress intensity factor being a scalar multiplier of the singular field. However, for a material particle at a small distance from the moving crack, the local stress field depends not only on instantaneous values of crack speed and stress intensity factor, but also on the past history of these lime-dependent quantities. A representation of the crack tip field is obtained in the form of an expansion about the crack up in powers of radial coordinate, with the coefficients depending on the time rates of change of crack tip speed and stress intensity factor. This representation is used to interpret some experimental observations, with the conclusion that the higher-order expansion provides an accurate description of crack tip fields under fairly severe transient conditions. In addition, some estimates are made of the practical limits of using a stress intensity factor field alone to characterize the local fields.