Stress intensity factors in two bonded elastic layers containing cracks perpendicular to and on the interface—I. Analysis (original) (raw)
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Closed form expression\ are obtained for the \tres\es at a crack tip when a crack is approaching a welded boundary (or a free surface) and when it has just passed through the interface. The solutions which are obtained in terms of a small pxameter. the distance from or through the interface. are given in explicit form for the mode 3 situation and for \ome mode I and 2 ca\es. The importance of the change of stress singularity when the crack meet\ the interface i\ demon\tr;ttrd. On the stress intensity factory x~ociated with cracks 491
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Different expressions are used in the literature for the stress intensity factors of interface cracks between anisotropic material. In particular, two of these approaches will be discussed and compared for orthotropic and monoclinic materials. Relations between the stress intensity factors will be found. Expressions for the interface energy release rate G i are presented. Although the expressions appear different, they are shown to be the same by using the relations between the stress intensity factors. Phase angles are defined which may be used in a fracture criterion.
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A-4 the basis of the first of the three general hypotheses proposed, a new interpretation of the J-integral has been given that leads to the same expressions as given by Rice. Furthermore, expressions are given as functions of the geometry and of the crack length for merent fracture parameters such as total fracture energy, the energy required to break a specimen from a certain point, the Tearing Modulus and the J value. However, the most meaningfid aspeot concerns the new interpretation of fracture on the basis of hypothetzes that are more general than the elasto-plastic deformation models; as a consequence, the exposed theory may also be applied to materials that do not follow such models, which are basically particular cases of the hypotheses presented here. The proposed method is complementary to the classical one and it is not a&ted by the large percentage errors made measuring initial crack growth.
Fontanari V.: ‘Stress intensity factors for a Subsurface crack in a two dimensional half-space
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Mode I and II Stress Intensity Factors (SIFs) under general loading conditions were determined for a crack parallel to the surface in a two-dimensional half space. To this purpose, a parametric Finite Element (FE) analysis of the subsurface crack was set up, and the analyses were conducted for independent loading conditions. Symmetric and anti-symmetric for both normal and tangential loads were considered and the corresponding SIFs were determined at the two crack tips. Several distances of the crack with respect to the surface were analysed and general functions representing the SIFs versus this parameter were obtained by interpolating the FE results. For both KI and KII, influence coefficients were defined reproducing the FE results with a satisfactory accuracy. When the crack approaches the surface the loss of symmetry was demonstrated to produce coupling effects between modes I and II of fracture. This effect is quantified and some consequences for a general loading condition di...
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Experimental stress intensity factors (SIFs) for two interacting straight cracks in planehomogeneous regions were determined. Photoelastic data were collected from digitally sharpened isochromatic fringe patterns by using a digital image analysis system. SIFs were extracted by using the field equations derived from Williams' stress function. Numerical SIFs were also obtained by the boundary integral equation method. Good agreement was observed between experimental and numerical results. NOTATION crack tips as shown in Fig. 4 one-half crack length one-half horizontal distance between crack tips A and D one-half vertical distance between crack tips B and C one-half length of specimens specimen thickness one-half width of specimens orientation of crack AB with respect to the long direction of the specimens polar coordinates as shown in Fig. 9 applied far-field tensile stress stress intensity factor mode I SIF mode II SIF term used to normalize SIFs (= o/;;;; in this study) Young's Modulus Poisson's Ratio material fringe value
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