Stress intensity factors for cracks in structures under different boundary conditions (original) (raw)
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International Journal of Fracture, 1993
An efficient boundary weight function method for the determination of stress intensity factors in a twodimensional mixed mode cracked body with arbitrary shape and subjected to arbitrary loading is presented in this study. The functional form of the boundary weight functions for modes I and II are successfully demonstrated by using the least squares fitting procedure. Explicit boundary weight functions are presented for rectangular plates of finite width and length containing edge and central cracks. If the stress distribution of a cut out rectangular cracked plate from any arbitrary shape of cracked body subjected to arbitrary loading is determined, the stress intensity factors K~ and Kn for the cracked body can be obtained from the predetermined boundary weight functions by a simple integration. Comparison from the literature of the calculated results with some solutions by other workers confirms the efficiency and accuracy of the proposed weight function method.
Stress intensity factors and weight functions for a corner crack in a finite thickness plate
Engineering Fracture Mechanics
The failure of cracked components is governed by the stresses in the vicinity of the crack tip. The singular stress contribution is characterised by the stress intensity factor K. Stress intensity factors depend on the geometry of the component and on the special loading conditions (tension, bending, thermal stresses,...). A procedure for their determination is the weight function technique where the weight functions are only dependent on the crack geometry. Stress intensity factors and weight functions are reported for many practical problems in handbooks. In this report new solutions for stress intensity factors and weight functions are compiled in form of tables or approximate relations.
ESTIMATION OF STRESS INTENSITY FACTOR (SIF) ON CRACK COMPONENT BY USING FINITE ELEMENT ANALYSIS
Theoretical solutions are available for idealized cases such as Infinite flat plate with edge crack, central crack etc. However main limitation of these theoretical solutions is they are very restrictive and while analyzing a normal component, a lot of assumptions go into it. Finite Element Analysis on the other hand provides good tool to determine Stress Intensity Factor. Cracks generally initiate at geometric discontinuities (such as notches, holes, weld toes, voids etc.) that induce large stress (stress concentration). Since crack growth is related to the effective stress intensity factor (SIF) which is at crack tip, the evaluation of Stress Intensity Factors. The present work would aim to fulfill this gap and generate more information thereby increased understanding on fracture behavior in 3D Components. Finite element analysis has been performed to support the results on fracture parameters like Location and Size of Cracks and results has been compared with available theoretical solutions. It is concluded that magnitude of critical Stress Intensity Factor can be used as a fracture criterion for thin Plates. Same procedure has been adapted for Analysis of connecting rod to find Stress Intensity Factor at various lengths of crack
2012
A comparison between six models, calculating stress intensity factor (SIF) mode I for central cracked plate with uniform tensile stress, is made in order to select the suitable model. These models are three theoretical models (i.e. classical model) and three numerical models. The three numerical models are half ANSYS model, quarter ANSYS model (finite element method) and weight function model. The geometry of the cracked plate (the width of the plate, the length of the plate and the crack length) and applied stress are the parameters that used to compare between the models. The three theoretical models can recognize the effect of the width of the plate, the crack length and applied stress but they failed to recognize the effect of the length of the plate. The three numerical models are success to recognize the effect of geometry and loading parameters. But the half ANSYS model gives a different response to the variation of the (H/W) ratio and that occurs due to finding the stress in...
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)'
ESTIMATION OF STRESS INTENSITY FACTOR OF A CENTRAL CRACKED PLATE
iaeme
There are two, parallel ways to investigate the geometry effect on fracture toughness: experimental and computational analysis, the latter referring often to Finite Element Method (FEM). This investigation is on central cracked plate of a finite length. Basically stress Intensity factor is calculated here analytically and computationally. ANSYS 11.0 is used as a computational tool. For different values of uniform pressure, stress intensity factor is calculated and then compared with analytical results and good agreement is noted between both approaches
Stress intensity factor evaluation for central oriented cracks by stress dead‐zone concept
Material Design & Processing Communications
The concept of the stress dead zone (SDZ) at the crack vicinity of a plate submitted to a uniform tensile condition is key in the simplification of fracture characterization, in particular, in the calculation of the stress intensity factor (SIF). The stress field close to a crack face can be negligible in any structure, and thus, the corresponding region would be discarded from the initial structural component contributing to suppress the crack tip singularity. The computation of the Griffith compliance method based on disregarding this area can thereby be done with simple analytical formulations following linear elastic fracture mechanics principles. In this study, the SDZ concept was considered, together with the compliance function, to formulate the SIF analytical solution.
Materials, 2021
The aim of this study is to obtain the stress intensity factor (SIF) along the crack front of elliptical cracks located in finite-thickness plates subjected to imposed displacement or applied tensile load, for different crack geometries (relative depths and aspect ratios) and crack configurations (embedded, surface, and corner). The SIF was calculated from the J-integral, obtained by the finite element method. The results show how the SIF grows with the increase in the relative crack depth and with the decrease in the aspect ratio, with the corner crack being the most dangerous configuration and the embedded crack the most favorable configuration. By increasing the plate length, the SIF rises when the plate is under imposed displacement and decreases when the plate is subjected to applied tensile load, both cases tending towards the same SIF curve.
International Journal of Fatigue, 2007
A hybrid weight-function technique is presented. It consists of dividing an elliptical crack into two zones, then using the appropriate weight function in the area where it is more efficient. The proportion between zones is determined by optimizing two crack parameters (axis ratio and curvature radius). Stress intensity factors for plates containing elliptical and semi-elliptical cracks are hence computed by a self developed computer code. Static and fatigue loadings of bending are considered. The results found by the present approach are in good correlation with the analytical solutions (when available) as well as with those of other researchers.
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.