Stress intensity factor sif calculations for semielliptical surface crack in round bars subjected to a combined loading using a threedimensional finite element fe model was numerically presented. This weight function approach is applied to a semi elliptical crack at blade mounting locations by considering the stresses. The sif for deep semielliptical surface crack in finite thickness plates determined by. Loadcarrying cruciform fillet welded joint is commonly encountered in onshore and offshore structures. Calculation of the stress intensity factors for elliptical. The stress intensity factor ki is a key parameter used in the fracture. Estimation of stress intensity factors for semielliptical. Stress intensity factor, semielliptical surface crack, pressure vessel, stress concentration, finite element analysis solution of displacement field the integrity of major components of process equipment industry should be evaluated and maintained during operation. Fracture analysis of a semielliptical surface crack in.
It is supposed that the crack growth direction coincides with the jintegral vector. Influence of effective stress intensity factor range on mixed mode fatigue crack propagation. Stress intensity factors for elliptical and semielliptical cracks. Stress intensity factor, surface crack, crack propagation, fatigue, fracture mechanics. It is found that when the embedded depth is 4 times larger than the minor semiaxis of the ellipse, the weld surface effects on the crack can be. A weight function is proposed for the calculation of the stress intensity factors for the deepest point of the crack.
Comprehensive investigation of stress intensity factors in. 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. Fonte md, ereitas md 1499 stress intensity factor for semielliptical sdce cracks in round has under bending and torsion. Therefore, determination of fracture parameters under different working conditions is an essential issue. Stress intensity factor of semielliptical surface crack in internally. Computation of the stress intensity factor ki for external longitudinal. These have been derived by finite element analysis of the welded joint ignoring the presence of residual stresses. An effective and accurate process of computing closedform stress intensity factors is employed which. The engineering methods of the sif calculation can be efficient when the following. The behavior of semielliptical surface flaws in cylinders is of interest in the technology of pressure vessels. 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. Numerical and experimental investigation of mixedmode. The stress intensity factor sif for semielliptical surface cracks subjected to mode i and mode iii loading was found by using a three dimensional finite element method. The magnitudes of these stresses at a given point are entirely dependent on k.
Threedimensional analysis of a semielliptical crack. The most effective method of evaluating the stress intensity factor induced by an applied stress field is by using the weight function for a. 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. A zareei 2 calculated the stress intensity factor at the deepest point of the semielliptic crack and proposed the weighting function of the high aspect ratio semielliptical crack on the basis. In this paper, an embedded elliptical crack in a weld of pressure vessels under tension was taken into consideration, and stress intensity factors at the crack tip were calculated numerically with the emphasis on the influences of the weld 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 cracks dtic. Stress intensity factors for surface cracks in round bar. Some of these solutions are based on the use of thinshell theory18, which does not take into account the three dimensional nature. Pdf dynamic stress intensity factors for a longitudinal. 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. Different crack aspect ratio, ab ranging between 0. Stress intensity factors in a rotating impeller containing semielliptical.
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 stress intensity factor of semielliptical axial cracks. Prediction of stress intensity magnification factors of a. 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. Semielliptical surface crack an overview sciencedirect topics. Determination of weight functions for semielliptical surface cracks by direct adjustment to reference stress intensity factor solutions. The coefficients of these functions are determined assuming piece wise polynomial stress distribution along the crack. Since many rock types show brittle elastic behaviour under hydrocarbon reservoir. Because this stress field is asymptotic dominant or singular, it is characterized by the stress intensity factor sif.
For an arbitrary threedimensional crack the effective stress intensity factor is calculated through the value of the jintegral. Influence of effective stress intensity factor range on. Kassir and sih determined the stress incensity factor of an elliptical crack. Deepdyve is the easiest way to get instant access to the academic journals you need.
Approximative twoterms weight function derived from one reference case. Dynamic stress intensity factors for a longitudinal semielliptical. A semielliptical crack modeling and fracture constraint. Stress intensity factor analysis for partelliptical cracks in structures. Read local thermal stress intensity factors for an axial semielliptical crack in a hollow cylinder using the finite element method, strength, fracture and complexity on deepdyve, the largest online rental service for scholarly research with thousands of academic publications available at. However, in most practical cases the deepest point a fig. The dynamic stress intensity factors are derived for an internal longitudinal semielliptical crack in a thickwalled cylinder subjected to transient dynamic stresses. Stress intensity factor for a semielliptical crack subjected to an. Department of mechanical engineering, the university of hong kong, pokfulam road, hong kong. The weight function was then applied to a wide range of semielliptical surface cracks subjected to nonlinear loadings. Lets say we have within a structural member an elliptical hole of major axis 2a with radius of curvat.
Due to the nonpenetrating fillet welds at the intersection of the main plate and transverse. Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in. Results of scc crack growth for threedimensional semielliptical cracks are presented. Dotfaaar95111 stressintensity factors for elliptical.
The relative difference for shorter cracks depths was between 2 to 5% if compared to the literature value. Analysis of internal circumferential semielliptical cracks with high aspect ratio in pipes. K is not to be confused with the elastic stress concentration factor k t. 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. K is called a stress field parameter, or stress intensity factor. Finally, the dynamic stress intensity factors are extracted for both the deepest and surface points of the semielliptical crack using the weight function method. Stress intensity factor of a wide range of semielliptical. To determine the stress intensity factors for a semielliptical crack in a plate. An effective method for computing the elastic field in a finite cracked disk. Calculation of stress intensity factors and crack opening.
Stress intensity factors and weight functions for longitudinal semielliptical surface cracks inside thickwalled cylinders using highlyrefined finiteelement models. This revised cefm accurately predicted the dependence of crack growth rates on the stress intensity factor and offers an. Stress intensity factor for a semielliptical crack subjected to an arbitrary. Calculation of stress intensity factors for elliptical. The effect of various erosion configurations on the mode i stress intensity factor sif distribution along the front of a semielliptical crack, emanating from the deepest line of the erosion surface dles at the bore of an autofrettaged, pressurized thickwalled cylinder of outer to inner radius ratio, r o r i 2, is investigated. Stress intensity factors for surface cracks in round bars. Stress intensity factor k stresses in the vicinity of the crack tip are dependent on r, and k. The problem is, from a diagram i have, it seems the first one is the quarterelliptical corner crack and the latter is the edge. Pdf stress intensity factor for a semielliptical crack subjected to. In addition, some new solutions for stress intensity factors for pressurised thin outer to inner radii. Stress intensity factors for semielliptical surface cracks under arbitrary stress distributions are hardly available for surface cracks with aspect ratios of ac1. First consider a conventional strength of materials approach. Stress intensity factors of semielliptical surface cracks in pressure.
In this paper, a comprehensive study of stress intensity factors sifs in rotating disks containing threedimensional 3d semielliptical cracks subjected to different working conditions is carried out. Dynamic stress intensity factors for a longitudinal semi. In this investigation, the weight function method was employed to calculate the stress intensity factors for semielliptical surface crack in a hollow cylinder. Comprehensive investigation of stress intensity factors in rotating. Stressintensity factors for semielliptical surface. There are various stress intensity factor solutions, particularly for flat plates and pressure vessels with various cracked geometries. An effective and accurate process of computing closedform stress intensity factors is employed which can be used for any kind of boundary conditions. Stress intensity factors of semielliptical surface cracks in pressure vessels by.
Comparison of the fatigue behaviour of the semielliptical. Stress intensity factors for a semielliptical surface crack. Stressintensity factor for a wide range of semielliptical surface cracks in finite thickness plates. Therefore, the weight functions for the point a and b have been derived analogously to. Modified stress intensity factor equations for semielliptical surface. 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. Nomenclature a semielliptical crack depth b semielliptical crack semiwidth b disc specimen thickness c disc halfwidth c v distance from centre of indent to crack tip d disc specimen width e youngs modulus h hardness k c fracture toughness k i openingmode stress intensity factor k ii slidingmode stress intensity. Solutions are known for pure tension and bending as proposed by newman and raju.
Stress intensity factors for elliptical and semielliptical cracks subjected to an arbitrary mode i loading. Deepdyve is the largest online rental service for scholarly research with thousands of academic publications available at your fingertips. An effective closed form expression is proposed to evaluate the stress intensity factors. Stress intensity factor determination plays a central role in linearly elastic fracture mechanics lefm problems. Stress intensity factor for elliptical cracks physics forums. Normalised stress intensity factors for surface crack at centre of hole in a plate. Semielliptical surface cracks at the centre of a hole in a finite plate subjected to. A wellknown procedure for the estimation of stress intensity factors for arbitrary stresses is the evaluation of an upper and a. Modeling of 3d scc crack growth with sgbemfem alternating. 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.
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