Stress field

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

Tectonic and gravitational stress in long symmetric ridges and valleys

Abstract: We present an exact elastic solution for the effects of topography on the near-surface stresses caused by a uniform, uniaxial tectonic compression or tension acting normal to the axial planes of isolated symmetric ridges and valleys of realistic shape. The solution, obtained by the Kolosov-Muskhelishvili method of complex potentials, gives stresses in the vicinity of these topographic features that, with the exception of the vertical component, are of the order of the regional tectonic stress. The effect of topography is to reduce a regional tectonic compression near the crest of a ridge and, if the ridge is sufficiently steep, to cause a stress reversal resulting in a small tension. Valleys, on the other hand, concentrate the far-field tectonic stress. When a previously derived exact solution for the topographic effect on the gravity-induced stress field is combined with the present solution for the topographic modification of a regional compressive tectonic stress, we find a slight increase in the lateral components of the gravity-induced compressive stress at the ridge crest and, under the valley bottoms, a decrease in the gravity-induced tensile stresses. The opposite effects occur when a far-field tension is superposed on the gravity-induced stress field.

Influence of Deformation-Induced Martensite on Fatigue Crack Propagation in 304-Type Steels

Abstract: This research reports an investigation into the influence of mechanically induced martensitic transformation on the rate of fatigue crack growth in 304-type austenitic stainless steels. Two steels of different composition, 304L and 304LN, were used to test the influence of composition; two test temperatures, 298 and 77 K, were used to study the influence of test temperature; and various load ratios were used to determine the influence of the mean stress. It was found thadecreasing the mechanical stability of the austenite by changing composition or lowering temperature reduces the fatigue crack growth rate and increases the threshold stress intensity for crack growth. However, this beneficial effect diminishes as the load ratio increases, even though increasing the load ratio increases the extent of the martensite transformation. Several mechanisms that may influence this behavior are discussed, including the perturbation of the crack tip stress field, crack deflection, work hardening, and the relative brittleness of the transformed material. The perturbation of the stress field seems to be the most important; by modifying previous models, we develop a quantitative analysis of the crack growth rate that provides a reasonable fit to the experimental results.