Stress concentrations occur when there are irregularities in the geometry or material of a structural component that. Constant amplitude crack growth technical background. The stress intensity factor of a semi elliptical crack in a tshaped welded joint. Ghazali, effect of crack faces opening mechanisms on the combined stress intensity. The stress intensity factor ki which is called the modei stress intensity factor and. The behavior of semielliptical surface flaws in cylinders is of interest in the technology of pressure vessels. Maximum stress intensity factors of a surface crack usually appear at the deepest point of the crack, or a certain point along the crack front near the free surface depending on the aspect ratio of the crack. 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 critical stress intensity factors k c for some engineering materials are grouped in the. For several metals, including carbon steels, aluminum alloys, brass, and. India abstract a semielliptical crack in a thick walled cylinder has been considered for the analysis.
The aim of this article is to calculate stress intensity factors ki, kii and kiii along the semielliptical crack front using the ansys code. The distribution of the values of sif along the crack front, obtained using the empirical. 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. Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in.
For both the semi circular and semi elliptical surface crack the stress intensity factors were larger for larger values of crack depthtoplate thickness ratio. 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. Computation of the stress intensity factor ki for external. The general form of the stress intensity solution for any crack can be described as. This page provides stress intensity factor solutions for common cases. Closed form stress intensity factors for a semielliptical crack in a thickwalled cylinder under thermal stress, international journal of fatigue 28. The problem is, from a diagram i have, it seems the first one is the quarterelliptical corner crack and the latter is the edge. 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. Deepdyve is the easiest way to get instant access to the academic journals you need.
Variations of stress intensity factors of a semielliptical. Engineering methods for deformation, fracture, and fatigue, 3rd edition elliptical surface crack in plate. Effect of crack shape on fatigue crack growth fatigue and. The stressintensity factor for the circumferential semielliptical surface cracks in a hollow cylinders cross section under torsion is calculated using a finiteelement technique. Stressintensity factors for semielliptical surface cracks. These cracks then grow into semielliptical shapes while extending into the shaft. Stress intensity factor for an elliptical crack approaching. The object of this study is to determine the stress intensity factor distribution around the crack front under arbitrary loading conditions for a longitudinal semielliptical flaw with ac and rit 10. Stress intensity factors for elliptical and semielliptical cracks subjected to an arbitrary mode i loading. 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. Stressintensity factors for semielliptical surface. In this investigation, the weight function method was employed to calculate stress intensity factors for semi elliptical surface crack in a hollow cylinder.
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. Stress concentrations occur when there are irregularities in the geometry or material of a structural component that cause an interruption to the flow of. The variation of stressintensity factor sif at the surface kc and at the depth. In fact, over 30 years ago a national academy of sciences. Transient stress intensity factors of functionally graded. Stress intensity factors for surface semielliptical crack. Unlike kirschs solution, it is applicable to an infinite number of different scenarios. The author proposes an equation for calculating the stress intensity factor sif for a semielliptical surface crack for uniform, linear, and quadratic laws of variation of the load applied to its edges. In the present work the exact analytical sif solution has been obtained for an elliptical crack embedded in an infinite elastic body and subjected to an arbitrary applied normal stress field mode i. However, it has long been recognised that a semielliptical weld toe crack cannot be accurately represented by a 2d approximation due to the 3d nature. A semielliptical surface crack is assumed having the initial crack depth a0.
Stress intensity factor for an embedded elliptical crack approaching the free surface of a semi infinite solid and subjected to a linearly varying pressure is presented in a nondimensional form as a function of position around the crack periphery, crack aspect ratio, and crack distance from the free surface. Analysis of semielliptical crack in a thick walled cylinder using fem yugal kishor sahu1, s. Hence it was necessary to fit a 5 th order polynominal. Traditionally, the weld magnification factor has been determined from 2d plane strain models containing edge cracks. Accurate critical stress intensity factor griffith crack. Like kirschs solution for the circular hole 2, it applies to an infinite isotropic plate in uniaxial tension. Comprehensive investigation of stress intensity factors in rotating disks containing threedimensional semi elliptical cracks m. They were evaluated using a solution from the sintap stress intensity factor handbook 4 for a semielliptical surface crack in a plate subject to throughwall stress profile expressed as a 5 th order polynominal. Finite element method analysis of stress intensity factor. I am using abaqus to model a 3d circular crack to calculate stress intensity factor. Fonte md, ereitas md 1499 stress intensity factor for semi elliptical sdce cracks in round has under bending and torsion. Weld toe magnification factors are widely used in the evaluation of stress intensity factors for cracks in welded structures. The problem is, from a diagram i have, it seems the first one is the quarter elliptical corner crack and the latter is the edge.
Download limit exceeded you have exceeded your daily download allowance. Stress intensity factor determination for threedimensional. Figure 3 presents data on an aluminum alloy and 7030 brass in addition to. In addition, a recent threedimensional fe study on the sif of a tshaped welded joint was reported in reference. 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. Stress intensity factor for a semi elliptical crack. Moulick2 address for correspondence 1research scholar, b. Semielliptical surface crack an overview sciencedirect.
Determination of stress intensity factor and interaction. Approximate stress intensity factor solutions for semi. Weld joint stress intensity and residual stress profiles twi. Fonte md, ereitas md 1499 stress intensity factor for semielliptical sdce cracks in round has under bending and torsion. Applied mathematics and mechanics, volume 38, issue 11. Early theoretical solutionsfor surface flaw problems usually involved the discussion of semicircular or semielliptical cracks in semiinfinite solids refs. Stress intensity factors for surface cracks in round bar. There are various stress intensity factor solutions, particularly for flat plates and pressure vessels with various cracked geometries. Calculation of stress intensity factors and crack opening a. Deepdyve is the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Lets say we have within a structural member an elliptical hole of major axis 2a with radius of curvat. On the other hand, the max stress is predicted to go to infinity as the ellipse flattens to form a crack \b \rightarrow 0\.
Pearson1 has recently discussed the problem of the rate of growth of a fatigue crack. First consider a conventional strength of materials approach. Hi, i just wanted some clarification with respect to a few equations relating stress intensity factor to semielliptical and quarterelliptical cracks in solids. I have already partitioned the model well and used fine mesh around the crack tip region. The stress intensity factors k i and k ii for an inclined central crack on a plate subjected to uniform tensile loading were calculated for different crack orientations angles using finite element fe analysis, which was carried out in abaqus. 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. Stress intensity factors and fatigue growth of a surface. Calculating stress intensity factors for a semielliptical.
Therefore, the weight functions for the point a and b have been derived analogously to. It is a theoretical construct usually applied to a homogeneous, linear elastic material and is useful for providing a failure criterion for brittle materials. Stress intensity factors determination for an inclined. However, in most practical cases the deepest point a fig. Stress intensity factors for semielliptical surface cracks in platetoplate butt welds with parallel misalignment of same thickness. Stress intensity factor solutions for semielliptical weld. Stress intensity factors for elliptical and semielliptical. Stress intensity factors of semi elliptical surface cracks in finitethickness plates 823 1.
Stressintensity factors for a wide range of semielliptical. A list of the critical stress intensity factors fracture toughness for common materials. Stress intensity factors for semielliptical surface. A uniform stress and a linear stress distribution were used as the two references to determine the weight functions. 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. Early theoretical solutionsfor surface flaw problems usually involved the discussion of semi circular or semi elliptical cracks in semi infinite solids refs. Stress intensity factor of a wide range of semielliptical. Stress intensity factor for a semi elliptical crack subjected to an arbitrary mode i loading. Because this stress field is asymptotic dominant or singular, it is characterized by the stress intensity factor sif.
Fracture propagation is controlled by the stress field near the crack tip. Critical stress intensity factor k ic has been an approximation for fracture toughness using only loadcell measurements. Stress intensity factors for elliptical and semielliptical cracks subjected to an arbitrary mode l. 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. It is mostly accepted that the stress intensity factor sif is calculated in the. 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. However, it has long been recognised that a semi elliptical weld toe crack cannot be accurately represented by a 2d approximation due to the 3d nature of the geometry. Kassir and sih determined the stress incensity factor of an elliptical crack. For both the semicircular and semielliptical surface crack the stressintensity factors were larger for. The exact analytical sif solutions for an elliptical crack were obtained only for some particular cases of polynomial applied stress fields. Finite element investigation of stress intensity factors. He tabulated values of the stress intensity factor k necessary to cause a crack to grow under a repeated.
The sif values of circular crack are higher at the crack surface. Proceedings of bitcon2015 research paper analysis of. Stress intensity factors for elliptical and semi elliptical cracks subjected to an arbitrary mode i loading. This transformation is convenient for generating the mesh, and it has. However, generally it has been difficult to obtain smooth distributions of stress intensity factors along the crack front accurately due to the effect of a corner point singularity. Fatigue cracks nucleate at the surface of the shaft operating under cyclic load.
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. Improved formula for the stress intensity factor of semi. Effect of brace wall thickness and weld size on stress intensity factors for. Stress intensity factor for an embedded elliptical crack approaching the free surface of a semiinfinite solid and subjected to a linearly varying pressure is presented in a nondimensional form as a function of position around the crack periphery, crack aspect ratio, and crack distance from the free surface. Mechanisms of stresscorrosion cracking asm international. For an elliptical crack in an infinite body under uniaxial tension the maximum. How can i calculate the stress intensity factor of semi. The derivation of the equation is based on the wellknown newmanraju solution for a bent plate. For plates with semi elliptical surface crack, newman, raju and kou have reported the stress intensity factor. 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.
The problem is solved for a semicircular crack front and various crack inclination angles. For the tensile tests the bars were glued in brass cylinders with an epoxy resin. Stress intensity factors and weight functions for a void with an annular crack chapter 19 displacements. The defect studied in this survey has a form of a longitudinal semi elliptic crack, located on. For this reason, results for finite geometry stress intensity factors are usually reported in terms of. Stress intensity factor determination plays a central role in linearly elastic fracture mechanics lefm problems. The critical stress intensity factors k c for some engineering materials are grouped in the following categories toughness of metals. The stress intensity factors were obtained using the j integral method. Pdf stress intensity factors for circumferential semi. Hereafter, the term equilibrium crack shape means either semielliptical or semicircular. This study attempts to analyze the stress intensity factor in various edge cracks along the length of a finite plate which is under a uniform tension. Stress intensity factors for surface semielliptical crack in. The sif results in reference were used to further validate the accuracy of the modified formula.
Stress intensity factor solutions for internal longitudinal. Stress intensity factor for elliptical cracks physics forums. 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. The results reveal that the compressive loading cannot eliminate the branching process. Finite element investigation of stress intensity factors of. Calculation of stress intensity factors and crack opening. Therefore, an evaluation based on the threshold stress intensity factor range. Two cracks with the same stress intensity will have the same behavior. Some of these solutions are based on the use of thinshell theory18, which does not take into account the three dimensional nature.
He tabulated values of the stress intensity factor k necessary to cause a crack to grow. The behavior of semi elliptical surface flaws in cylinders is of interest in the technology of pressure vessels. 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. On the other hand, for the semielliptical surface crack crack depthtocrack half length ratio of 0. Dotfaaar95111 stressintensity factors for elliptical. However, artificial manmade cracks several orders of magnitude longer and wider than natural flaws have required a correction factor term y that can be up to about 3 times the recorded experimental value. The weight function represents the sif induced by a unit concentrated load.
The geometry factor y depends only on the geometry of the specimen and the geometry of the crack front. Jul 01, 2004 read variations of stress intensity factors of a semi elliptical surface crack subjected to mode i, ii, iii loading, international journal of pressure vessels and piping on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. Since many rock types show brittle elastic behaviour under hydrocarbon reservoir. To obtain similar ke values for brass and aluminium alloy, for which he. Stress intensity factors for elliptical cracks dtic. In this report, we emplo the domain integy ral method to obtain the mode i stress intensity factor distributions for elliptical and straight cracks emanating from a centrall located countersunk y rivet hole in a square plate subjected to remote tension. Calculation of stress intensity factors for elliptical crack. On the other hand, for the semi elliptical surface crack crack depthto crack half length ratio of 0. Improved formula for the stress intensity factor of semielliptical.