Influence of crack offset distance on interaction of multiple collinear and offset edge cracks in a rectangular plate (original) (raw)
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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.
Applied Science and Engineering Progress
An adaptive remeshing and photoelasticity techniques are presented to determine the stress intensity factors K I and crack-hard inclusion interaction of a single edge cracked plate for two-dimensional fracture mechanics problems. The paper starts from describing two-dimensional linear fracture mechanics theory and an adaptive remeshing H method using the quadrilateral and triangular elements. The computational procedure and related finite element equations are explained. The photoelastic theory and its experimental procedure with the use of the stress optic laws are then described. The photoelasticity prototype is designed and built. Performance of adaptive remeshing method is evaluated by analyzing a single edge cracked plate made from polycarbonate. A crack plate with a hard inclusion is then studied for stress intensity factor and crack-hard inclusion interaction. The hard inclusion is made from aluminum. The K I stress intensity factor is found to be a function of the crack length per width. The results of adaptive remeshning method and the photoelasticity technique are compared with Brown's study. This example demonstrates the efficiency of the adaptive remeshing method to provide accurate solutions as compared to those from the photoelastic technique. Then, crack-hard inclusion interaction is studied by varying stress intensity ratio and E ratio. The crack-hard inclusion interaction behavior is formulated in exponential equation, i.e. cracking tip shielding function. The cracking tip shielding function shows that maximum stress intensity ratio reduces rapidly if E ratio increases. The normalized stress intensity factor is as a convergence exponential function of E ratio.
Stress Intensity Factors For Plates With Collinear And Non-Aligned Straight Cracks
2012
Multi-site damage (MSD) has been a challenge to aircraft, civil and power plant structures. In real life components are subjected to cracking at many vulnerable locations such as the bolt holes. However, we do not consider for the presence of multiple cracks. Unlike components with a single crack, these components are difficult to predict. When two cracks approach one another, their stress fields influence each other and produce enhancing or shielding effect depending on the position of the cracks. In the present study, numerical studies on fracture analysis have been conducted by using the developed code based on the modified virtual crack closure integral (MVCCI) technique and finite element analysis (FEA) software ABAQUS for computing SIF of plates with multiple cracks. Various parametric studies have been carried out and the results have been compared with literature where ever available and also with the solution, obtained by using ABAQUS. By conducting extensive numerical stud...
Experimental Techniques, 2009
L ife prediction of single or multi-material products is one of the most important studies in engineering design and maintenance. Crack propagation speed and its trajectory are the key behaviors to assess the life of products. Determination of the stress intensity factors on crack tip are needed to accurately predict the crack propagation and its trajectory. Several numerical methods and nondestructive experimental techniques are currently being used to determine such phenomena. The photoelastic technique with an optic-experimental interference has been employed to determine the stress intensity factors and the crack's trajectories. 1-4 Its principle is based on the double refraction phenomenon by analyzing the maximum shear stress induced in the transparent or birefringent of the photoelastic model under loading. The phenomenon is observed by looking through the optical elements, i.e. the polarizer and the analyzer of the polariscope, as demonstrated in . Their results provide information that can be applied directly to metal prototypes by using the law of similarity. At present, several numerical methods have also been developed to predict crack propagation phenomenon. These methods include the finite element method, 5-7 the meshless method, 8,9 the manifold method with virtual crack extension, 10 and the boundary element method. 11
Photoelastic investigation of crack-inclusion interaction
Experimental Mechanics, 1990
An experimental procedure is presented for determining the mode I stress-intensity factor of an edge crack with a nearby rigid elliptical inclusion in a finite plate loaded in uniform tension. The, rigid inclusion was modeled by bonding two identical steel inclusions on to the faces of a thin plate of polycarbonate. Models were constructed with edge cracks and various inclusion geometries so that the effect of parameters such as inclusion shape, orientation, and cracktip position on the stress-intensity factors of the crack could be determined. Photoelasticity experiments were used for this investigation and the results were compared to the results of a similar theoretical analysis of the interaction between a crack and an inclusion in an infinite plate. A good correlation was found between the experimental and theoretical models indicating that the results may help provide a better understanding of the toughening mechanisms in materials such as short-fiber-reinforced composites and ceramics. This experimental method is relatively easy to use making it an attractive candidate to be applied to similar problems involving cracks and inhomogeneities.
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
Dynamic crack curving—A photoelastic evaluation
Experimental Mechanics, 1983
A dynamic-crack-curving criterion, which is valid under pure Mode i or combined Modes 1 and II ioadings and which is based on either the maximum circumferential stress or minimum strain-energy-densitY factor at a reference distance of ro from the crack tip, is verified with dynamic-photoelastir, experiments. Directional stability of a Mode I crack propaga-1 . Kx.2 2 tion is attained when ro = ~-(~--) V6 (c,cl,c2)>r~, where r~ = 1.3 mm for Homalite-lO0 used in the dynamicphotoetastic experiments.
Evaluation of stress intensity factor of multiple inclined cracks under biaxial.PDF
A finite rectangular plate of unit thickness with two inclined cracks (parallel and non parallel) under biaxial mixed mode condition are modelled using finite element method. The finite element method is used for determination of stress intensity factors by ANYSIS software. Effects of crack inclination angle on stress intensity factors for two parallel and non parallel cracks are investigated. The significant effects of different crack inclination parameters on stress intensity factors are seen for lower and upper crack in two inclined crack. The present method is validated by comparing the results from available experimental data obtained by photo elastic method in same condition.
Influence of crack offset distance on the interaction of multiple cracks on the.PDF
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.