Modeling of edge cracks interaction (original) (raw)
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Modeling of edge cracks interaction.PDF
From experimental and theoretical investigations it is known that cracks are sensitive to geometry, e.g., to the inclination angle to the load. A small deviation of a crack from the normal direction to a tensile load causes mixed mode conditions near the crack tip which lead to deviation of the crack from its initial propagation direction. Besides, the presence of other cracks, inhomogeneities, surfaces and their interaction causes additional deformations and stresses which also have influence on the initiation of the crack propagation and on the direction of this propagation. The aim of this paper is to show the effects of the interaction of edge cracks on further crack formation. The main fracture characteristics, such as, stress intensity factors, fracture angles and critical loads are provided in this study. A series of illustrative examples is presented for different geometries of arbitrarily inclined edge cracks.
International Journal of Automotive and Mechanical Engineering, 2013
Shielding interaction effects of two parallel edge cracks in finite thickness plates subjected to remote tension load is analyzed using a developed finite element analysis program. In the present study, the crack interaction limit is evaluated based on the fitness of service (FFS) code, and focus is given to the weak crack interaction region as the crack interval exceeds the length of cracks (b > a). Crack interaction factors are evaluated based on stress intensity factors (SIFs) for Mode I SIFs using a displacement extrapolation technique. Parametric studies involved a wide range of crack-to-width (0.05 ≤ a/W ≤ 0.5) and crack interval ratios (b/a > 1). For validation, crack interaction factors are compared with single edge crack SIFs as a state of zero interaction. Within the considered range of parameters, the proposed numerical evaluation used to predict the crack interaction factor reduces the error of existing analytical solution from 1.92% to 0.97% at higher a/W. In refe...
Interactions of double slanted cracks under mode I loading
MATEC Web of Conferences
This paper presents numerical analysis of double slanted central cracks in square plates under mode I tension stress. ANSYS finite element program is used to model and solve the problem of slanted cracks where the stress intensity factor is determined according to J-integral approach. Three relative crack length, a/W = 0.1, 0.2 and 0.3 is used while relative spacing between the cracks, s/2a are ranged between 0.1 to 0.6. In order to study the roles of slanted cracks on the stress intensity factor, several slanted angles are used such as 0 o , 15 o , 30 o , 45 o , 60 o and 75 o . According to the numerical analysis, all parameters above played an important role in determining the stress intensity IDFWRUV $V H[SHFWHG ORQJHU FUDFN SURGXFHG KLJKHU VWUHVV LQWHQVLW\ IDFWRU )RU WKH FUDFNV ZLWK D: LQVLJQLILFDQW crack interaction is observed however when crack reached a/W=0.3, the interaction is gradually increased. Increasing the slanted angles slightly increased the interaction factor however the effect of relative crack spacing became insignificant.
The interaction of two parallel non-coplanar identical surface cracks under tension and bending
International Journal of Pressure Vessels and Piping, 1999
In this paper, the interaction between two identical, non-coplanar, semi-elliptical surface cracks is investigated. The interacting cracks are assumed to be in an infinite plate subjected to remote tension or to pure bending loads. The stress intensity factors (SIFs) for these cracks are calculated using three-dimensional linear finite element analysis. A parametric study involving the relative horizontal and vertical separation distance between the two surface cracks is carried out for a specific crack shape and crack depth to plate thickness ratios of 0.3 and 0.2, respectively. An empirical formula is derived that relates the effects of the relative positions of these cracks to their SIFs. ᭧
Stress intensity factors for interacting cracks
Engineering Fracture Mechanics, 1987
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
Frattura ed Integrità Strutturale
In the present work finite element method has been employed to study the interaction of multiple cracks in a finite rectangular plate of unit thickness with cracks on the same side under uniaxial loading conditions. The variation of the stress intensity factor and stress distribution around the crack tip with crack offset distance has been studied. Due to the presence of a neighbouring crack, two types of interactions viz. intensification and shielding effect have been observed. The interaction between the cracks is seen to be dependent on the crack offset distance. It is seen that the presence of a neighbouring crack results in the appearance of mode II stress intensity factor which was otherwise absent for a single edge crack. It can be said that the proximity of cracks is non-desirable for structural integrity. The von-Mises stress for different crack orientations has been computed. Linear elastic analysis of state of stress around the crack tip has also been done.
Interacting Cracks Analysis Using Finite Element Method
2012
This chapter aims to introduce the concept of fracture mechanics and numerical approaches to solve interacting cracks problems in solid bodies which involves elastic crack interaction. The elastic crack interaction is a result of changes in stress field distribution as the applied force is given during remote loading. The main emphasis is to address the computational evaluation on mechanistic models based on crack tip displacement, stress fields and energy flows for multiple cracks.
International Journal of Fracture, 1982
This paper reports on an attempt to investigate the stress intensity factors of equal and unequal oblique parallel edge cracks subjected to tension. The effects of the variation of the length of the cracks, angle of inclination, and crack spacings on the stress intensity factors (opening and sliding modes) were studied. Experimental observations show that, for crack spacings equal or larger than the length of the equal oblique parallel edge cracks, the size of the caustics for the cracks in the loaded specimen approach that of a single oblique edge crack with the same angle of inclination. In the case of unequal oblique parallel edge cracks, a crack closure phenomenon and its occurrance with respect to the length of the cracks and crack spacings were investigated. It was observed that the transverse diameter of the caustic for the shorter cracks became small and negligible when the position of the shorter cracks with respect to the longer cracks became smaller than half of the crack spacings.
The interaction of two inclined cracks with dynamic stress wave loadings
International Journal of Fracture, 1992
To gain insight into the phenomenon of the interaction of stress waves with material defects and the linkage of two cracks, the transient response of two semi-infinite inclined cracks subjected to dynamic loading is examined. The solutions are obtained by the linear superposition of fundamental solutions in the Laplace transform domain. The fundamental solution is the exponentially distributed traction on crack faces proposed by Tsai and Ma [-1]. The exact closed form solutions of stress intensity factor histories for these two inclined cracks subjected to incident plane waves and diffracted waves are obtained explicitly. These solutions are valid for the time interval from initial loading until the first wave scattered at one crack tip returns to the same crack tip after being diffracted by another crack tip. The result shows that the contribution of diffracted waves to stress intensity factors is much less than the incident waves. The probable crack propagation direction is predicted from the fracture criterion of maximum circumferential tensile stress. The linkage of these two cracks is also investigated in detail.