The objective of this study is to determine the stress intensity factor for cracks emanating from a shaft by using finite element method and also to verify the finite element results with those obtained semianalytically. S szngularity element i isoparametrlc element y x b element pattern around crack front on the ith plane. Stress intensity factors for inclined external surface. Semielliptical surface crack an overview sciencedirect topics. From semielliptical shaped flaw tests with a2c ratios between 0. Stress intensity factor, surface crack, crack propagation, fatigue, fracture. K is not to be confused with the elastic stress concentration factor k t. Improved formula for the stress intensity factor of semi. Modified stress intensity factor equations for semielliptical surface. An uniform stress and a linear stress distributions were used as the two references to determine the weight function. Stress intensity factors for elliptical and semielliptical cracks subjected to an arbitrary mode l. The magnitudes of these stresses at a given point are entirely dependent on k.
In this investigation, the weight function method was employed to calculate stress intensity factors for semielliptical surface crack in a hollow cylinder. Stress intensity factors for elliptical and semielliptical cracks. The most effective method of evaluating the stress intensity factor induced by an applied stress field is by using the weight function for a given cracked body. Stress intensity factors for a wide range of longdeep. A stress intensity factor sif which includes this effect increases the accuracy of fatigue lives prediction. The smith theory will be compared with the theories of. K is called a stress field parameter, or stress intensity factor. The weight functions were then applied to a wide range of semielliptical surface crack subjected to nonlinear loadings. The plates were subjected to either remote tension or bending loads. The problem is solved for a semicircular crack front and various crack inclination angles. The stress intensity factor, is used in fracture mechanics to predict the stress state stress intensity near the tip of a crack or notch caused by a remote load or residual stresses. These unknown parameters can be determined from reference stress intensity factor and t. Brief note on the stress intensity factor of elliptical cracks.
However, for plates with partly throughwall cracks, namely an semi elliptical crack with an imaginary crack depth a which is greater than the thickness t of the plate, the stress intensity factor was not reported. Stressintensity factors of semielliptical surface cracks in finitethickness plates 819 this model idealizes one eight of. Evaluation of the formula of stress intensity factor k i. However, when calculating the sif of a semielliptical crack, this. The expense of replacement and time out of service have made repairing policy more attractiv. Their solution is applicable to a wide range of crack and plate. Stress intensity factors of eccentric cracks in bi. For cracked pipes, the equation for mode i stress intensity factor at any point along an elliptical or semielliptical crack in raju and newman 1982 can be extended for the stre ss intensity factors with mixed modes for an inclined crack with the consideration of the inclination angles as follows. Stress intensity factors for a wide range of semi elliptical surface cracks in.
Stress intensity factor for cracks emanating from a shaft. A semielliptical crack modeling and fracture constraint on failure diagram. Pdf we use the weight function for an elliptical crack embedded in an infinite elastic media in conjunction with the alternating method to. For plates with semi elliptical surface crack, newman, raju and kou have reported the stress intensity factor. Stress intensity factors for surface cracks in round bar. This method is used to derive the weight functions for both k and t for semi. Accurate stress analyses of surfacecracked components are. The purpose of this paper is to present stressintensity factors for a wide range of nearly semielliptical surface cracks in pipes and rods. Improved formula for the stress intensity factor of semielliptical. Parametric equations for the stress intensity factor are used to obtain the generalized stress parameter. Hence, there is a great need to determine the stress intensity factor in cracked shafts by using finite element method. In these equations, the newman and raju equation for a semi elliptical surface crack in a plain plate is chosen as the base stress intensity equation.
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. A semielliptical crack modeling and fracture constraint. The allowable stress of a part can be calculated with the stress intensity factor. In this investigation, the weight function method was employed to calculate the stress intensity factors for semielliptical surface crack in a hollow cylinder. Stress intensity interaction between dissimilar semi. The stress intensity factor for cracks emanating from a notchtip, fig. This paper presents stress intensityfactor influence coefficients sifics for axially and circumferentially oriented finitelength semielliptical innersurface flaws with aspect ratios total.
In this report, we emplo the domain integy ral method to obtain the mode i stressintensity factor distributions for elliptical and straight cracks emanating from a centrall located countersunk y rivet hole in a. The effect of the weld toes in welded joints is considered using a weld toe magnification factor m k, and the scf equations are taken into account for misalignment. Fonte md, ereitas md 1499 stress intensity factor for semielliptical sdce cracks in round has under bending and torsion. The y term allows the effects of finite width, crack shape, position along crack front, bulging, stress concentration factors, local stress concentration. Stressintensity factor influence coefficients for a wide range of semielliptical surface cracks on the inside or outside of a cylinder are presented. Stress intensity factors of a semielliptical crack in a hollow cylinder. The sif results in reference were used to further validate the. In this investigation, the weight function method was employed to calculate stress intensity factors for semi elliptical surface crack in a hollow cylinder. The stress intensity factor solution given by isida et al. Some of these solutions are based on the use of thinshell theory18, which does not take into account the three dimensional nature. The mode 1 stress intensity factor sif distribution for numerous configurations of combined semicircular and semielliptical crackmore. For plates with semielliptical surface crack, newman, raju and kou have reported the stress intensity factor. In chapter 3, different solution approaches to the stress intensity factor for a semielliptical. Pdf stress intensity factors and weight functions for.
The relation between m f and the semielliptical shape ac, the relative crack depth ab, the variation of angle. There are various stress intensity factor solutions, particularly for flat plates and pressure vessels with various cracked geometries. A uniform stress and a linear stress distribution were used as the two references to determine the weight functions. The stress intensity factor of a semielliptical crack in a tshaped welded joint. Stress intensity factor of a wide range of semielliptical partly throughwall crack in a finitethickness plate. Stressintensity factors for a wide range of semielliptical surface. Numerical results of these coefficients are obtained for a wide range of geometric parameters. Figure 11 shows the results for a surface stress intensity factors of semi elliptical surface cracks in finitethickness plates 825 2,0 1. Stressintensity factors for a wide range of semielliptical surface cracks in.
Stress intensity factors for elliptical and semielliptical cracks subjected to an arbitrary mode i loading. It presented simple study on comparison between linearelastic stress intensity factor, k and elasticplastic jintegral in order to divined their character and accuracy. Weight functions for the determination of stress intensity. From the study of the experimental data, a general fatigue crack growth law is developed for the calculations of the fatigue life of the pipeline. The purpose of this research is to compare both british standard bs 7910 20 and american standard api 579asme ffs1 2016 stress intensity factor sif solutions by considering a series of semielliptical surface cracks located in the external surface of a pressurized hollow cylinder in the axial direction. Stress intensity factor of semielliptical surface crack in internally. Keywords crack length,fatigue crack growth, pressure vessel,stress intensity factor, semielliptical crack. Stress intensity factors for semielliptical surface cracks in a plate. Fracture analysis of a semielliptical surface crack in.
The stress intensity factors are presented for the deepest and surface points for semi elliptic cracks with aspect ratios of 005 and 01, and values of 02, 05, and 08. The overestimated y values for the entire range of crack depth are expected. This is also case in the asme xi appendix a where stress intensity factors k i formulations are given for a large range of crack depths and for a flaw aspect ratio al between 0 and 0. The similitude concept states that if the stress intensity k for a crack in the actual component and in the test specimen are the same, then the. The correction factor m f of sif at different point along the front of the crack is determined. Stress intensity factors for semielliptical surface cracks in platetoplate butt welds with parallel misalignment of same thickness. The 3d analysis is performed by the finite element fe method and the submodeling technique, employing singular elements along the crack front. Modified stress intensity factor equations for semi. The weight function was then applied to a wide range of semielliptical surface cracks subjected to nonlinear loadings. Surface cracks are among the more common flaws in aircraft and pressure vessel components. A series of detailed dimensional finite element two. Stress intensity factors for a wide range of longdeep semi elliptical surface cracks, partly throughwall cracks and fully throughwall cracks in tubular members author links open overlay panel k. 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 semielliptical surface crack in. Stress intensity factors for surface semielliptical crack.
The f factor is defined in equation 5, which reflects the growth range from. Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in. The stressintensity factor sif of the semielliptical surface crack in the finite body under extensional stress is sclculated by using the fem software ansys release 5. Pdf stressintensity factors for semielliptical surface cracks in.
Stress intensity factors for semi elliptical surface cracks ac 0. Pdf stressintensity factors for internal and external. Therefore, an evaluation based on the threshold stress intensity factor range. Stressintensity factors for semielliptical surface cracks in welded joints. Analysis of stress intensity factor along semielliptical. Stressintensity factors for semielliptical surface cracks under tension or bending. The paper concludes with a parametric study that provides a set of stressintensity factors for semielliptical surface cracks covering a practical range of crack sizes, aspect ratios and material property gradations under tension, bending. 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 stressintensity factors along the crack front. Determining stress intensity factor means in essence the derivation of the function.
A magnification factor is commonly used to multiply the sif of semielliptical surface cracks to account for the stress concentration effect in welded connections. Semielliptical surface cracks are one of the most frequent cracks found in many structures in service, such as offshore structures and aircraft components. Based on the data, a new correlation has been evolved to evaluate the stress intensity factor range. The stress intensity factor is generally expressed in the form k y. The stress intensity factors k 1 calculated by extrapolation from stresses and displacements and by the energy release rate agree well within a tolerance of about 10%. Read stress intensity factors for a wide range of longdeep semielliptical surface cracks, partly throughwall cracks and fully throughwall cracks in tubular members, engineering fracture mechanics on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Stress intensity factors for a semielliptical surface. Pdf stress intensity factors for circumferential surface.
Stress intensity factor of a wide range of semielliptical. Stressintensity factors for semielliptical surface cracks under. The aim of this article is to calculate stress intensity factors ki, kii and kiii along the semielliptical crack front using the ansys code. Dotfaaar95111 stressintensity factors for elliptical. However, for plates with partly throughwall cracks, namely an semielliptical crack with an imaginary crack depth a which is greater than the thickness t of the plate, the stress intensity factor was not reported. 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 configurations were subjected to either remote. Pdf stress intensity factor for a semielliptical crack subjected to.
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. Stress intensity factors for semielliptical surface. Fracture mechanics analysis of a pressure vessel with a. Mode i stress intensity factor on crack 2 when it is in proximity to the other crack. Finiteelement idealization for an embedded circular pennyshaped crack. Read stress intensity factor of semielliptical surface crack in a cylinder with hoop wrapped composite layer, international journal of pressure vessels and piping on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. Stress intensity factor of semielliptical surface crack. Stress intensity factor k stresses in the vicinity of the crack tip are dependent on r, and k. The weight function represents the sif induced by a unit concentrated load. This high stress concentration reduces fatigue lives of welded structures. Stress intensity factor interaction semielliptical crack structural integrity assessment.
The variations of the stress intensity factor k of the jintegral and of the crack tip opening displacement ctod along the crack front are presented and discussed. Stress intensity factor of semielliptical surface crack in. A generalized stress parameter approach for fatigue life. It is a theoretical construct usually applied to a homogeneous, linear elastic material and is useful for providing a failure criterion for brittle materials, and is a critical technique in the discipline of. Figures 11 and 12 shows stress intensity factors obtained by several investigators for a semi elliptical surface crack in a finitethickness plate. Fatigue crack growth prediction of a semielliptical. Stressintensity factor equations for cracks in three. The boundary element method is employed to determine polynomial influence coefficients of stress intensity factors, k i, for a semielliptical crack in internally pressurized thickwalled curved tubing. In addition, a recent threedimensional fe study on the sif of a tshaped welded joint was reported in reference. Influence coefficients of stress intensity factors for.
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