Stress Intensity Factors For Plates With Collinear And Non-Aligned Straight Cracks (original) (raw)
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Numerical estimation of stress intensity factors in patched cracked plates
Engineering Fracture Mechanics, 1987
The fatigue and fracture performance of a cracked plate can be substantially improved, by providing patches as reinforcements. The effectivenessof the patches is related to the reduction they cause in the stress intensity factor (SIF) of the crack. So, for reliable design, one needs an accurate evaluation of the SIF in terms of crack, patchand adhesive parameters. In this investigation a finite element technique to compute the SIF through the J-integral for patched cracked plates is presented. TRIM6 and TRUMPL elements of ASKA are employed to model cracked sheet and cracked sheet-adhesives-patch regions, respectively. Path independency of J-integral for unpatched plates is shown by considering many contours. For patched plates, the contours chosen do not enclose the patch-cracked sheet region. The values of SIF's are obtained for unpatched edgecracked, un patched centre-cracked and patched centre-cracked plates. These values are compared with the analytical and numerical results existing in the literature. This study shows that conventional finite elements can be used to model patched cracks and reasonable estimate of SIF can be made via the i-integral. NOTATION IJ" CTy,a,y G" G,., GX>' E'. i-integral Contour surrounding the crack tip Traction vector defined according to the outward normal along r, Fig. I Displacement vector at a point on contour, ii = iu+jv Arc length along the contour Crack length and semi crack length for edge crack and centre-crack plates respectively Width and semi witith for edge-crack and centre-crack plates respectively Length of plates State of stress at a point (x, y) State of strain at a point (x, y) Young's modulus of the cracked plate Strain energy density, 1/2 (atGt +CTyEy +ax).Ex)'
Fracture Analysis in Typical Cracked Configurations
2014
Objective of the work is the fracture analysis of typical cracked configurations Finite element based fracture analysis has been carried out to the study the effect of flaws in typical components like rectangular plate, circular rod and a cylindrical pressure vessel, all of which are having application in launch vehicles. Analysis was done using ANSYS Workbench. Stress intensity factor in the presence of flaws has been estimated and compared with the values obtained using theoretical solution available.
Stress intensity factors for cracks in structures under different boundary conditions
Engineering Fracture Mechanics, 1990
In calculating stress intensity factor solutions for standard cases, the weight function and superposition technique have been used extensively. These solutions although valid for simple specimens present a problem in the case of statically indeterminate structures. The work described in this paper investigates the effect of boundary conditions on the stress intensity factor solution for an edge cracked plate, edge cracked ring and a surface cracked plate using the finite element technique.
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.
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.
The Effect of the Size and Position of the Crack on the Normalized Stress Intensity Factor
Algerian Journal of Renewable Energy and Sustainable Development
In this work, finite element method was used to determine the normalized stress intensity factors for different configurations. For this, a 2-D numerical analysis with elastic behavior was undertaken in pure I mode. This simulation was carried out using a numerical calculation code. On the basis of the numerical results obtained from the different models treated, there is a good correlation between the nodal displacement extrapolation method (DEM) and the energy method based on the Rice integral (J) to evaluate the normalized stress intensity factors and this for different crack lengths. For each configuration, the increase in the crack size causes an amplification of normalized intensity stresses fators.
Fuselage lap joints, wing chord-wise splices, rib to skin attachments and wing skins at run outs are typically susceptible to Multi-Site Damage (MSD). However, due to the differences in configuration, and the empirical nature of crack growth modeling, different crack growth models are better suited to different configurations. Therefore, there is a need to identify which models are best suited to each situation. As part of a broader research program, this investigation compared published geometry factors that were determined using the Finite Element Alternating Method (FEAM), Alternating Indirect Boundary Element (AIBE) method and handbook solutions. The models that were compared were for multiple embedded through cracks in a plate and multiple through cracks at holes. The comparison found minimal differences between the solutions. However, the scope of the comparisons was narrow, covering only a small proportion of possible crack configurations. Consequently, future work was identified including comparisons of a wider range of methods capable of developing geometry factors for a wider range of crack configurations.