Weight function method to determine stress intensity. This work presents stress intensity factors for a wide range of semielliptical surface cracks on the inside of pressurized cylinders. Kassir and sih 26 obtained the solution of the stress intensity factor for an elliptical crack in an infinite body under a remote uniform shear stress. Stress intensity factor sif, first introduced by irwin, is a physical quantity used as a control parameter to evaluate the critical state of a crack. Introduction three dimensional cracks such as a surface or. Fonte md, ereitas md 1499 stress intensity factor for semielliptical sdce cracks in round has under bending and torsion. The weight function method was applied and appropriate weight functions have been derived using the petroskiachenbach crack opening displacement expression. Due to the nonpenetrating fillet welds at the intersection of the main plate and transverse. Influence of the interaction on stress intensity factor of. Then, the t stress weight functions for the deepest. Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in a circular shaft under tension and bending. Influence of flaw shapes on stress intensity factors for. The paper concludes with a parametric study that provides a set of stress intensity factors for semielliptical surface cracks covering a practical range of crack sizes, aspect ratios and material property gradations under tension, bending.
The threedimensional equations of elasticity are solved for a flat elliptical crack which has nonuniform shear stresses applied to its surfaces. The effects of residual stress distribution and component. Pdf stress intensity factors for circumferential surface. Very good agreement is found between trends in stress intensity factor with changes in crack. Stress intensity factors for surface cracks in round bar. Improved formula for the stress intensity factor of semielliptical surface cracks in welded joints under bending stress. The results were validated against finite element data and compared with other analyses. Modified stress intensity factor equations for semi. Analysis of stress intensity factor along semielliptical surface crack reinforced by composite patching. Stress intensity interaction between dissimilar semi. As part of the sintap project, threedimensional finite element models have been used to obtain solutions of the stress intensity factors for throughthickness cracks in cylinders18 and 22. Furthermore, the influence of the interaction differs with the crack tip position along the front. The parameter k is a measure of the magnitude of the stress field in the region of the crack tip and is called the stress intensity factor.
Pdf stressintensity factors for semielliptical surface cracks in. Pdf stress intensity factor equations for cracks in. Stress intensity factor for a semielliptical crack. This paper attempts to propose a weight function method to determine stress intensity factors for high aspect ratio semielliptical cracks in cylindrical vessels. Stress intensity factor of semielliptical surface crack in internally pressurized hollow cylindera comparison between bs 7910 and api 579asme ffs1. Mixed mode stress intensity factors for semielliptical surface cracks. Afrlvawptr20033002, usaf damage tolerant design handbook.
In this study, the stress intensity magnification factors m km of such configuration containing a 3d semielliptical surface crack at the weld toe are analysed using 3d finite element analyses. The y term allows the effects of finite width, crack shape, position along crack front, bulging, stress concentration factors, local stress concentration. A stress intensity factor sif which includes this effect increases the accuracy of fatigue lives prediction. Assuming an isotropic material with linear elastic behavior, the stress field on any linear elastic body that holds a crack can be determined, according to irwin 1, as follows. A wellknown procedure for the estimation of stress intensity factors for arbitrary stresses is the evaluation of an upper and a. Fatigue crack growth prediction of a semielliptical. Rapid method of stress intensity factor calculation. Weight functions for tstress for semielliptical surface. Semielliptical surface cracks are one of the most frequent cracks found in many structures in service, such as offshore structures and aircraft. Stress intensity factor, approximate method, semielliptical cracks, multiple site damage 1. Stress intensity factors for semielliptical surface cracks in platetoplate butt welds with parallel misalignment of same thickness. The exact analytical solution for the normalised by a,mbna stress intensity factor at the middle surface of the shell was given as 2. Since the torsion loading is nonsymmetrical, the whole finite element model has been constructed, and the. Keywords crack length,fatigue crack growth, pressure vessel, stress intensity factor, semielliptical crack.
The stress intensity factors used to develop the equation were obtained from a previous threedimensional, finiteelement analysis of semielliptical surface cracks in finite. The stress intensity factor of a semielliptical crack in a tshaped welded joint. In the parametric study, the effects of the ratio of the surface crack depth to length ranged from 0. The stress intensity factor is generally expressed in the form k y. Stress intensity factor calculations for semielliptical surface cracks in round bars subjected to bending and torsion using a threedimensional finite element model are presented. The solution technique for multiple cracks in an infinite body has recently been developed by. The weight functions are derived based on three dimensional finite element analysis. Early theoretical solutionsfor surface flaw problems usually involved the discussion of semicircular or semielliptical cracks in semiinfinite solids refs.
The derived weight functions account for both the global weldment geometry and the weld profile. An empirical stressintensity factor equation for the. Calculation of sifs for semielliptical surface cracks in. Stress intensity factors for an embedded elliptical crack approaching the free surface of the semiinfinite solid that is subjected to uniform tension perpendicular to the plane of crack are presented in a nondimensional form for various crack aspect ratios and crack distances from the free surface. Stress intensity factors for small cracks at notches 955 eq. Approximate determination of stress intensity factor for. Constant amplitude crack growth technical background.
The variation of the stress intensity factor along the crack front and the strain energy release rate were computed, by the boundary integral equation method, for semi elliptical cracks on the. Stress intensity factors for semielliptical surface. In this paper, the stress intensity factor for a longitudinal semielliptical crack in the internal surface of a thickwalled cylinder is derived analytically and. In this study, in order to investigate the intensity of interaction, the stress intensity factor sif of interacting semielliptical surface cracks was evaluated by the finite element method and. In this study, the stress intensity factors of surface cracks under two assumed residual stress fields were calculated. Comparison of stress distributions ahead of a elliptical notches in infinite plates and b sharp and blunt notches. Two cracks with the same stress intensity will have the same behavior. The configuration of the semiellipse follows the equation b 2 s. Pdf stressintensity factor equations for cracks in.
The common topic of the studies is the investigation on the effect of the vessels radius to thickness ratio t c r c and the effect of crack geometry ratio ac on the stress intensity factor. Stress intensity factor of semielliptical surface crack in. The validity of the approximations and the results are judged by validation with results from alternative fully threedimensional cases. A method for calculating stress intensity factors for edge and surface cracks in weldments has been presented. A magnification factor is commonly used to multiply the sif of semielliptical surface cracks to account for the stress concentration effect in welded connections. Stress intensity factors for pressure vessel surface flaws and nozzle corner cracks1 the influence of the flaw shape on the variation of stress intensity factors along the crack front is examined for longitudinal inner surface flaws in pressure vessels, and for corner cracks present at the intersection of a pressure vessel and a nozzle. Coules department of mechanical engineering, university of bristol, bristol, bs8 1tr, uk article info article history. Analysis of stress intensity factor along semielliptical surface crack. Paper open access stress intensity factor for a semi. For the appropriate modeling of a welded component with a crack, it is important to understand the effects of residual stress distribution and the geometry of the component on the stress intensity factor of the surface crack. Semielliptical surface crack an overview sciencedirect. The sif results in reference were used to further validate the. Pdf stress intensity factors for internal surface cracks.
Stress intensity factor influence coefficients slmcs obtained from these solutions are then superimposed to obtain modei stress intensity. Loadcarrying cruciform fillet welded joint is commonly encountered in onshore and offshore structures. Stress intensity factors and fatigue growth of a surface crack in a drill. Improved formula for the stress intensity factor of semi. For this reason, results for finite geometry stress intensity factors are usually reported in terms of. Abstract this paper presents an empirical stress intensity factor equation for a surface cracks as a function of parametric angle, crack depth, crack length, plate thickness and plate width for tension and bending loads. Solutions are known for pure tension and bending as proposed by newman and raju. Variation of stress intensity factor and crack opening displacement of semielliptical surface crack. This paper presents the application of the weight function method for the calculation of elastic t stress for semielliptical surface cracks. Stressintensity factors for semielliptical surface. Stress intensity factors are determined numerically using an alternating technique with two.
Received 11 january 2016 received in revised form 27 july 2016 accepted 27 july 2016 available online 29 july 2016 dedicated to the late prof. In addition, a recent threedimensional fe study on the sif of a tshaped welded joint was reported in reference. For a semicircular surface crack in a semiinfinite solid and a semielliptical surface crack in a plate of finite thickness, smith, emery, and kobayashi 6, and kobayashi 7, respectively, used the alternating method to obtain stress intensity factors along the crack front. Stress intensity factors for semielliptical surface cracks under arbitrary stress distributions are hardly available for surface cracks with aspect ratios of ac1. Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in a. This high stress concentration reduces fatigue lives of welded structures. The ratio of crack depth to crack length ranged from 0. Fatigue, crack growth, stress intensity factor, circumferential semi elliptical surface crack. This paper numerically discusses stress intensity factor sif calculations for surface cracks in round bars subjected to single and combined loadings. On the other hand, for the semielliptical surface crack crack depthto crack half length ratio of 0.
For both the semicircular and semielliptical surface crack the stress intensity factors were larger for larger values of crack. Stress intensity interaction between dissimilar semielliptical surface cracks h. Rice the partthrough surface crack in an elastic plate. Improved formula for the stress intensity factor of semielliptical. If the weight function is known for a given cracked body, the stress intensity factor due to any load system applied to the body can be determined by. Pdf stress intensity factor for a semielliptical crack subjected to. Download limit exceeded you have exceeded your daily download allowance. Pdf variation of stress intensity factor and crack. Pdf a method for calculating stress intensity factors for edge and surface cracks in weldments has been presented. First, the weight function method for the calculation of t stress previously developed for twodimensional crack problems was extended for the t stress calculation for threedimensional crack problems. For a pressurized cylinder with hoop wrapped composite layer, its stress intensity factor k may be expressed as 1 k p i r i t. This paper presents empirical stressintensity factor equations for embedded elliptical cracks, semielliptical surface cracks, quarterelliptical corner cracks, semielliptical surface cracks at.
Therefore, an evaluation based on the threshold stress intensity factor range. In this paper, we use the weight function for an elliptical crack embedded in an infinite elastic media in conjunction with the alternating method to derive the exact analytical solution for the stress intensity factor for a semielliptical surface crack subjected to an arbitrary mode i loading. Stress intensity factor of semielliptical surface crack. Situation may well arise where the aspect ratio of cracks is larger than one. Both semicircular and semielliptical cracks are examined. The weight functions were then applied to a wide range of semielliptical surface crack subjected to nonlinear loadings. Prediction of stress intensity magnification factors of a. Introduction many investigations have shown that sudden failures of. Rajuan empirical stress intensity factor equation for the surface crack. Stress intensity factors in a rotating impeller containing. For both the semicircular and semielliptical surface crack the stress intensity factors were larger for larger values of crack depthtoplate thickness ratio. Guidelines for the analysis and design of damage tolerant aircraft structures, 2002. Stress intensity factor for a longitudinal semielliptical crack in a. Stress intensity factor for a semielliptical rail head crack under traction to cite this article.