Stress concentration

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

Effect of Width and Length on Stress Intensity Factors of Internally Cracked Plates Under Various Boundary Conditions

Abstract: This paper is concerned with the analysis of stress intensity factors of a strip with a longitudinal crack subject to tension and bending along its edges, and the tension of rectangular plates with a central crack. For both problems three types of boundary conditions, that is, stress conditions, displacement conditions and their combinations are considered. Analysis is based on Laurent expansions of the complex potentials satisfying the stress free relations along the crack. The expansion coefficients are determined from boundary conditions along outer edges, by using a perturbation technique in the first problem and a boundary collocation procedure based on resultant forces and mean displacements in the second problem. Numerical calculations are performed for various plate configurations, and the results are summarized in forms ready for practical use. The accuracy of numerical results are also examined, and they are regarded as correct up to four figures.

A Progressive Failure Model for Composite Laminates Containing Openings

Abstract: A progressive failure model is developed for laminated composites containing stress concentrations subjected to in-plane loading. The fundamental approach is to model a damaged lamina using a damaged ply constitutive relation in a simplified manner. The environmental effects including the thermal residual stresses and hygroscopic stresses arc taken into consideration. Parametric studies show that load increment only has little effect on the ultimate strength. When the number of elements for the finite element mesh increases to a certain value, the predicted ultimate strength approaches a stable value. The predictions for the ultimate strength, stress-strain behavior and the damage progression agree reasonably well with the experimental result.

Micromechanics of the brittle to plastic transition in Carrara marble

Abstract: Samples of Carrara marble were deformed at room temperature to varying strains at confining pressures spanning the range in mechanical behavior from brittle to plastic. Volumetric strain was measured during the experiments, and the stress-induced microstructure was characterized quantitatively using optical and transmission electron microscopy. The range of confining pressure over which transitional (or semibrittle) deformation occurs is 30–300 MPa. The macroscopic initial yield stress is constant for confining pressures greater than 85 MPa, whereas the differential stress at the onset of dilatancy increases with pressure up to 300 MPa. The dilatancy coefficient decreases rapidly with increasing pressure up to 100 MPa, and then asymptotically approaches zero for pressures up to 300 MPa. The work hardening coefficient increases with pressure up to 450 MPa; the pressure sensitivity is greatest for pressures up to 100 MPa. Active deformation mechanisms include microcracking, twinning, and dislocation glide. Transmission electron microscopy observations indicate that dislocation glide occurs, at least on a local scale, in samples deformed in the semibrittle field at pressures as low as 50 MPa and applied differential stress well below the critical resolved shear stress for glide on the easiest slip system. Cracks and voids frequently nucleate at sites of stress concentration at twin boundaries, at twin terminations, and at the intersection of twin lamallae. Geometries suggestive of crack tip shielding by dislocations are also observed. Stereological measurements indicate that at constant strain in the semibrittle field, the stress-induced crack density and anisotropy decrease with increasing pressure. Crack density and anisotropy in samples deformed to strains of 3–5% in the semibrittle field at pressures up to 120 MPa are comparable to those in the prefailure brittle sample, although an analysis of the energetics of deformation suggests that the ratio of brittle energy dissipation to total energy dissipation is at least 60% lower. We also detect a qualitative difference in the characteristic length of the cracks in the brittle and semibrittle fields. The mean dislocation density at constant differential stress increases significantly for samples deformed at pressures of 230 MPa and greater. Our results suggest that although semibrittle flow occurs over a wide range of pressure, the most marked changes in strain partitioning, and hence the style of deformation occur over a small range in pressure.

Anticrack model for pressure solution surfaces

Abstract: We propose that discrete solution surfaces originate at stress concentrations and propagate through rock as anticracks . As material is dissolved and removed, the anticrack walls move toward each other; stress and displacement fields are identical to those for the conventional opening crack, but with a change of sign. Observations of entire traces of solution surfaces are consistent with the anticrack concept: (1) the surfaces are bounded in extent; (2) the dissolved thickness varies from a maximum near the center to zero at the tips; and (3) the maximum dissolved thickness is proportional to the length of the surface. Local dissolution and in-plane propagation are suggested by the large isotropic compressive stress at the anticrack tip. Propagating solution surfaces will interact to form a regular array corresponding to some bulk strain rate. Anticracks may also interact with opening and shear cracks; observations of interacting solution surfaces, veins, and faults illustrate these configurations. Intersecting arrays of cracks, anticracks, and shear cracks operate to yield a mode of bulk deformation similar to diffusion-accommodated grain-boundary sliding in polycrystalline solids.