Stress concentration

About: Stress concentration is a research topic. Over the lifetime, 23250 publications have been published within this topic receiving 422911 citations.

Global patterns of tectonic stress

Abstract: Regional patterns of present-day tectonic stress can be used to evaluate the forces acting on the lithosphere and to investigate intraplate seismicity. Most intraplate regions are characterized by a compressional stress regime; extension is limited almost entirely to thermally uplifted regions. In several plates the maximum horizontal stress is subparallel to the direction of absolute plate motion, suggesting that the forces driving the plates also dominate the stress distribution in the plate interior.

Limitations to the small scale yielding approximation for crack tip plasticity

Abstract: Recent finite-element results by S G Larsson and A J Carlsson suggest a limited range of validity to the 'small scale yielding approximation,' whereby small crack tip plastic zones are correlated in terms of the elastic stress intensity factor It is shown with the help of a model for plane strain yielding that their results may be explained by considering the non-singular stress, acting parallel to the crack at its tip, which accompanies the inverse square-root elastic singularity Further implications of the non-singular stress term for crack tip deformations and fracturing are examined It is suggested that its effect on crack tip parameters, such as the opening displacement and J-integral, is less pronounced than its effect on the yield zone size

Fatigue Crack Propagation of Short Cracks

Abstract: Previous studies have shown that both threshold stress intensity factors and fatigue crack growth rates are dependent on crack size The average growth rates for very short cracks considerably exceed those given by conventional stress intensity-crack growth laws fitted to long crack data Elastic and elastic plastic fracture mechanics solutions are modified to predict this behavior of short cracks by introducing an effective crack length U into the solutions for intensity factors and the J integral method of analysis The threshold stress at a very short crack length approaches the fatigue limit of the ma­terial, and therefore the value of k can be obtained once the threshold stress intensity factor and the fatigue limit are known The accuracy of the term k in predicting crack growth rates for short cracks is found to be independent of the applied strain level It varies linearly with the grain size of material and can be considered at surface as a measure of the reduced flow resistance of surface grains due to their lack of con­straint

The effect of grain size and grain orientation on deformation twinning in a Fe-22 wt.% Mn-0.6 wt.% C TWIP steel

Abstract: We investigate the effect of grain size and grain orientation on deformation twinning in a Fe–22 wt.% Mn–0.6 wt.% C TWIP steel using microstructure observations by electron channeling contrast imaging (ECCI) and electron backscatter diffraction (EBSD). Samples with average grain sizes of 3 μm and 50 μm were deformed in tension at room temperature to different strains. The onset of twinning concurs in both materials with yielding which leads us to propose a Hall–Petch-type relation for the twinning stress using the same Hall–Petch constant for twinning as that for glide. The influence of grain orientation on the twinning stress is more complicated. At low strain, a strong influence of grain orientation on deformation twinning is observed which fully complies with Schmid's law under the assumption that slip and twinning have equal critical resolved shear stresses. Deformation twinning occurs in grains oriented close to 〈1 1 1〉//tensile axis directions where the twinning stress is larger than the slip stress. At high strains (0.3 logarithmic strain), a strong deviation from Schmid's law is observed. Deformation twins are now also observed in grains unfavourably oriented for twinning according to Schmid's law. We explain this deviation in terms of local grain-scale stress variations. The local stress state controlling deformation twinning is modified by local stress concentrations at grain boundaries originating, for instance, from incoming bundles of deformation twins in neighboring grains.

Brittle fracture propagation in rock under compression

Abstract: The results of studies ot the initiation and propagation of fracture front a single Grifith crack in a biaxial Compressive stress field are reported. In is concluded that Griffith's theory of brittle fracture offers a reliable prediction of the fracture initiation stress but that the resulting fracture propagation froth a single crack cannot account for the macroscopic fracture of a specimen. Some preliminary results of studies on crack arrays and on the effects of crack closure iii compression are presented. The applicability of these results to the prediction of rock fracture in predominantly compressive stress fields is discussed.[/p]