Approximate stress intensity factor solutions for semi elliptical cracks with large aw and cb. Stress intensity factor for semielliptical surface cracks loaded by. The stressintensity factor for the circumferential semielliptical surface cracks in a hollow cylinders cross section under torsion is calculated using a finiteelement technique. The configuration of standard semielliptical surface cracks is described using the outer surface cracklengths and the crack depths. There are various stress intensity factor solutions, particularly for flat plates and pressure vessels with various cracked geometries. This weight function approach is applied to a semi elliptical crack at blade mounting locations by considering the stresses. Weight functions and stress intensity factors for internal surface semielliptical.
These cracks then grow into semi elliptical shapes while extending into the shaft. Pdf semielliptical surface cracks in finitethickness. The equations are presented in terms of stress intensity k i rather than normalised stress intensity y or m m, m b and this style has been retained in fitnet annex a. Weight function and stress intensity factor for a semi elliptical surface saddle crack in a tubular welded joint. The stress intensity factor of a semielliptical crack in a tshaped welded joint.
The stress intensity factors are presented for the deepest and surface points for semielliptic cracks with aspect ratios of 005 and 01, and values of 02, 05, and 08. Fonte md, ereitas md 1499 stress intensity factor for semi elliptical sdce cracks in round has under bending and torsion. Newman and raju nr 2, 3, 4 published approximate solutions for the geometry factor of semielliptical cracks under tension and bending mx, which are. The coefficients of these functions are determined assuming piece wise polynomial stress distribution along the crack. The weight function method is an efficient technique to calculate the stress intensity factors using uncracked stress field. The behavior of semi elliptical surface flaws in cylinders is of interest in the technology of pressure vessels. However, no similarly elegant stress intensity factors for circumferential semi elliptical surface cracks in pipes 5, 6, although related solutions are available for internal circumferential. The geometry considered for a pipe in raju and newman, 1986 is shown in fig. Stress intensity factor solutions for semi elliptical weldtoe cracks in tbutt geometries stress intensity factor solutions for semi elliptical weldtoe cracks in tbutt geometries weld toe magnification factors are widely used in the evaluation of stress intensity factors for cracks in welded structures.
Pdf stress intensity factors for circumferential surface. Comparison of stress intensity solutions for a crack at an edge notch in a semi infinite plate a ab 12, b ab 1 and c ab 2. Stressintensity factor equations are presented for an embedded elliptical crack, a semielliptical surface crack, a quarterelliptical corner crack, a semielliptical surface crack along the bore of a circular hole, and a quarterelliptical corner crack at the edge of a circular hole in finite plates. Detailed assessment of the predictive accuracy of the approximate solutions. Newman and raju obtained results for remote tension and bending and presented their results using an empirical equation. Abstract weld toe magnification factors are widely used in the evaluation of stress intensity factors for cracks in welded structures. Stress intensity factors for elliptical and semi elliptical cracks subjected to an arbitrary mode i loading.
Stress intensity factor solutions for nozzle corner cracks 315 finite element procedure was used by raju and newman for the solution of semi elliptical surface flaws in thin plates. Stressintensity factors for surface cracks in functionally. Approximate stress intensity factor solutions for semi. Stress intensity factor for a semielliptical crack subjected to an. The sif results in reference were used to further validate the accuracy of the modified formula. This paper considers mode i stress intensity factors for a tshaped geometry, representative of one flange and part of the web of a steel 1section, which contains a flat semi elliptical surface crack in. A uniform stress and a linear stress distribution were used as the two references to determine the weight functions. Stress intensity factors for elliptical and semielliptical cracks. All cracks are located in the same plane at the same distances, in the middle of the body and the applied stress is perpendicular to the cracks plane.
Stress intensity factors for surface cracks in round bar. Stress intensity factor solutions for semielliptical surface cracks in finite thickness plates were obtained using the fem by newman and raju, shiratori et al. Several crack tip stress intensity factor solutions have been published for semi elliptic, surface breaking cracks in plates subjected to tension or bending forces. For the verification purposes, the stress intensity factors solutions were obtained by using finite element method based computer program.
Stress intensity factor equations for internal semi. Raju proposed stress intensity factor solutions for circumferential semielliptical surface cracks in pipes i. Weight functions for the surface and the deepest point of an internal longitudinal semi elliptical crack in a thickwall cylinder r i t 1 were derived from a general weight function and two reference stress intensity factors. Approximate determination of stress intensity factor for. The solution from the british standard provided consistent results compared to finite element fe results for crack depth not much higher than. The combined use of a solution for an elliptical crack subjected to a polynomial. Therefore, the weight functions for the point a and b have been derived analogously to. For several linear and nonlinear crack face stress, fields, the weight functions were validated against finite. The paper presents numerical estimation of stress intensity factor sif of such cracks in circular solid shaft when subjected to bending and twisting loads in elastic conditions. Weight functions and stress intensity factors for internal surface semi.
Semielliptical surface cracks in finitethickness plates. The aim of this article is to calculate stress intensity factors ki, kii and kiii along the semi elliptical crack front using the ansys code. The stress intensity factor is generally expressed in the form k y. Pdf stress intensity factors and weight functions for. Includes solutions for tension and bending around both major axes. The results are compared to finite element solutions given in the literature. But, because of the complexities of such problems, exact solutions are not available. Figures 2a and 2b schematically show a lapshear specimen and a squarecup specimen, respectively, used to investigate the strength and fatigue lives of spot welds. The problem is solved for a semi circular crack front and various crack inclination angles.
The compendia for the stressintensity factor solutions for. New shape function solutions for fracture mechanics analysis. The y term allows the effects of finite width, crack shape, position along crack front, bulging, stress concentration factors, local stress concentration due to welds, etc. Weight functions for the determination of stress intensity.
Pdf stress intensity factors for circumferential semi. Stress intensity factors for elliptical cracks dtic. Journal of strain analysis for engineering design, 404, 3026. If the crack is not located centrally along the width, i. Fatigue cracks nucleate at the surface of the shaft operating under cyclic load. Pdf stress intensity factor for a semielliptical crack subjected to.
Stress intensity factors for a semielliptical surface. Improved formula for the stress intensity factor of semi. 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 semi elliptical surface crack subjected to an arbitrary mode i loading. A computational study of local stress intensity factor. Recently, several investigators have studied some of these problems using different analytical procedures and experimental methods. Approximate stress intensity factor solutions for semielliptical cracks with large a w and cb. Weight function and stress intensity factor for a semi. The stress intensity factor of a semi elliptical crack in a tshaped welded joint. The results reveal that the compressive loading cannot eliminate the branching process.
The second solution involves stresses in the half space due to prescribed normal and shear stresses on the surface. Stress intensity factors for surface semielliptical crack in. Approximate stress intensity factor solutions for semielliptical cracks. Weight functions and stress intensity factors for semi. Stress intensity factor, approximate method, semi elliptical cracks, multiple site damage 1. 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. The object of this study is to determine the stress intensity factor distribution around the crack front under arbitrary loading conditions for a longitudinal semi elliptical flaw with ac and rit 10. The semielliptical surface crack a solution by the alternating method. In order to calculate the fatigue life of cylinders subjected to internal pressure using the fracture mechanics approach, the stress intensity factors sifs for internal semi elliptical cracks are needed. Mixedmode stress intensity factors at the surface and deepest points of quarter elliptical corner cracks in mechanical joints such as bolted or riveted joints are analyzed by weight function method.
Calculation of stress intensity factors and crack opening a. 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. Stress intensity factors for circumferential semielliptical. Stress intensity factor for a semielliptical crack subjected. Includes solutions for tension and bending around both major. Nov 01, 2001 stress intensity factor solutions for semi elliptical surface cracks in finite thickness plates were obtained using the fem by newman and raju, shiratori et al.
Mar 29, 2019 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. This paper presents stress intensity factor influence coefficients sifics for axially and circumferentially oriented finitelength semielliptical innersurface flaws with aspect ratios total. Approximate stress intensity factor solutions for semielliptical cracks with large aw and cb. Calculation of stress intensity factors for a crack subjected to a complex stress. Development of stress intensity factor solutions for. However, in most practical cases the deepest point a fig. If the crack is located centrally in a finite plate of width and height, an approximate relation for the stress intensity factor is.
Stress intensity factors for elliptical and semielliptical. Comparison of stress intensity solutions for a crack at an edge notch in a semiinfinite plate a ab 12, b ab 1 and c ab 2. The paper includes an initial parametric study and discussion of k ivalues calculated for a number of semielliptical, surfacecrack geometries in. The second solution is for the stress eld in a semiin nite or nite body subjected to the. Prediction of stress intensity factors in semielliptical weld toe cracks in offshore tubular joints, proceedings of the 10 th international symposium and euroconference on tubular structures, april, dusseldorf, germany, pp. Stress intensity factor solutions for semielliptical weldtoe cracks in tubular kjoints s. Stress intensity factor of semielliptical surface crack in. In this investigation, the weight function method was employed to calculate stress intensity factors for semi elliptical surface crack in a hollow cylinder.
Stress intensity factors for an elliptical crack approaching the surface. These unknown parameters can be determined from reference stress intensity factor and t. In addition, a recent threedimensional fe study on the sif of a tshaped welded joint was reported in reference. Semielliptical cracks at notches the fatigue cracks emanating from notches are most often semielliptical. Instead, investigators have had to use approximate analytical methods, experimental methods, or engineering estimates to obtain the stress intensity factors. Includes solutions for tension and bending around both major axes detailed assessment of the predictive accuracy of the approximate solutions. Stress intensity factor solutions for internal longitudinal. Semi elliptical cracks at notches the fatigue cracks emanating from notches are most often semi elliptical.
Introduction three dimensional cracks such as a surface or. This method is used to derive the weight functions for both k and t for semi. Raju proposed an empirical stress intensity factor equation for a semielliptical surface crack in a finite plate under tensile stress 22 in the following form. 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. This page provides stress intensity factor solutions for common cases. The stress intensity factor solution given by isida et al. Stress intensity factor solutions for semielliptical weld. The weight function for an elliptical crack was subsequently employed in the alternating method to obtain the unique sif solution for a surface breaking semi. Some of these solutions are based on the use of thinshell theory18, which does not take into account the three dimensional nature of the highly localised stresses in the vicinity of the crack front.