Then, the variations of stress intensity factors of single and double surface cracks with different coatingsubstrate materials, different crack length. A uniform stress and a linear stress distribution were used as the two references to determine the weight functions. The stress intensity factor for a deep surface crack in a finite plate. Stressintensity factors for internal and external surface. Stressintensity factors for circumferential through cracks in hollow cylinders subjected to combined tension and bending loads. The only cracked body con guration which has been studied analytically for all types of. The new solution was compared with the earlier newmanraju equation. Stressintensity factors for small surface and corner cracks in plates. 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.
The aim of this study was to investigate the crack of a cylinder. N umerical evaluation of elastic stress intensity factors by the boundaryintegral equation method, the surface crack. With these influence coefficients, the stress intensity factor can be calculated for a wide range of surface crack geometries. Stress intensity factors for partthrough surface cracks. This work presents stressintensity factors for a wide range of semielliptical surface cracks on the inside of pressurized cylinders. The stress intensity factor solution developed here was incorporated into the fatigue crack growth program nasaflagro, which is widely used by the aerospace community. 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.
Region iii is characterized by rapid, unstable crack growth. The estimation of applied stress intensity factor, k i, and limit load, l r, for a given crackcomponent geometry are critical inputs to a fitnessforservice calculation. Surface crack propagation analysis under residual stress. Stress intensity factors for semielliptical surface. Stress intensity factors for a surface crack in a tubular. The effects of residual stress distribution and component. Pdf stressintensity factor equations for cracks in three. The stress intensity factor solutions for these crack cases are of great practical interest. Technical basis for the revised stress intensity factor. Stress intensity factor sif as a key conception of linear elastic fracture mechanics is proposed to describe the stress field of crack tip. Article pdf available december 1995 with 189 reads. For surface flaw problem, however, the stress intensity factors deviated. Stress intensity factor at the maximum penetration point.
The effect of corrosion patch geometry on stress intensity. 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. An investigation on the stress intensity factor of surface. Pdf this study attempts to provide complete solutions for the surface cracks and the effect of finite width using the weight function and other. When plates or shells are welded together, there is invariably some degree. Pdf stress intensity factors for internal surface cracks. Stressintensity factors for surface cracks in functionally graded materials under modei thermomechanical loading matthew c. The stress intensity factor describes the stress state at a crack tip, is related to the rate of crack growth, and is.
Stress intensity factors due to surface crack propagation were analysed by using the influence function method and inherent strain analysis of the residual stress fields caused by welding. Stress intensity factors and fatigue growth of a surface crack in a drill. Fonte md, ereitas md 1499 stress intensity factor for semielliptical sdce cracks in round has under bending and torsion. Several crack and tsection geometries are analysed, for both tension and bending, using the finite element method. Once the crack appeared, the conception of stress is no longer applicable because of the stress singularity at the crack tip. Fortunately, for simple crack geometries like elliptical and circular cracks, there exist analytical formulae for mode i stress intensity factor variation along the crack tip which help us to evaluate the accuracy of the numerical modeling and. Department of civil and environmental engineering, university of illinois at urbanachampaign. It is based on fitting the distribution of the stress normal to the plane of the crack in the uncracked body, over the depth of the crack, with a cubic equation. Stress intensity factor and load limit solutions for. The stressintensity factors used to develop the equation were obtained from a previous threedimensional, finiteelement analysis of semielliptical surface cracks in finite. Stress intensity factors for a semielliptical surface.
The stress intensity, k i, represents the level of stress at the tip of the crack and the fracture toughness, k ic, is the highest value of stress intensity that a material under very specific planestrain conditions that a material can withstand without fracture. The experimental stress intensity factors can be extracted from the well known paris equation 5 d a d n c. Stress intensity factors of surface cracks in coatingsubstrate system under cylindrical indenter is investigated. Evaluating stress intensity factors of a surface crack in lubricated. The crack growth rate accelerates as the maximum stress intensity factor approaches the fracture toughness of the material. 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 in a plate containing two collinear through cracks, ah 1, fig. The weight function method was applied and appropriate weight functions have been derived using the petroskiachenbach crack opening displacement expression. Stress intensity factors for surface cracks in round bar. An empirical stressintensity factor equation for the. Effect of weld residual stress fitting on stress intensity.
The derived weight functions account for both the global weldment geometry and the weld profile. The threedimensional finite element method and the leastsquares method were used to find the stress intensity factors sifs of a surface crack in a lubr. Fatigue, crack growth, stress intensity factor, circumferential semielliptical surface crack. Crack opening displacements and stress intensity factors are also obtained for a throughthickness, center cracked bar with variable thickness. The sif at the crack is presented by the influences of mechanical and geometrical characteristics. Stress intensity factor solutions for surface cracks in flat plates subjected to nonuniform stresses. Stress intensity factor of semielliptical surface crack in internally. Mode i stress intensity factors of sickleshaped surface. Many of these solutions are found in computer programs and handbooks. Then, the influence of the crack propagation angle on the stress intensity factors is determined, along the crack front, on 1200 chs tjoint with semielliptical surface crack. The y term allows the effects of finite width, crack shape, position along crack front, bulging, stress concentration factors, local stress concentration. Stress intensity factor investigation of critical surface. 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.
The coefficients of this equation are used with correction factors given in the code to calculate the stress intensity factors at the deepest point of the crack and near the free surface. An empirical stressintensity factor equation for the surface crack. Accurate stressintensity factor solutions for these components are needed for reliable prediction of crackgrowth rates and fracture strengths. A method for calculating stress intensity factors for edge and surface cracks in weldments has been presented. The finite element method 3d is used to determine stress intensity factor sif at critical positions. The reported results show a considerable potential for using this method in calculating stress intensity factors for commonly encountered surface crack geometries in finite solids. The problem is analyzed by determining displacement potentials that satisfy reduced wave equations and specified boundary conditions. The crack surfaces were subjected to four stress distributions. 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 damage tolerance. The new solution in tabular form was then used directly in the weightfunction method. At high stress intensities, crack growth rates are extremely high and little fatigue life is involved.
Shin cs, cai cq 2004 experimental and finite element analyses an stress intensity factors of an elliptical surface crack in. K m where dadn is the crack growth rate which is obtained from the experimental test. 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 the flange. The initial residual stress in a plate with a welded butt joint was calculated by using inherent strain analysis, and the redistribution of residual stress and the stress intensity factor due to crack. An empirical stressintensity factor equation for the surface crack developed by rawe and used in ref. Stress intensity factor of semielliptical surface crack in. Fourteen different solutions for the stressintensity factors are compared. K is the range of the stress intensity factor, c and m are material constants. This section will present a catalog of stressintensity factor solutions for some typical crack geometries.
Validation of surface crack stress intensity factors of a. The stress intensity factor is abbreviated sif and represented by the variable, \k\. Stress intensity factor at the maximum penetration point of a semielliptic surface crack in an infinite plate under pure bending. Stress intensity factor solutions for surface cracks in. Rice the partthrough surface crack in an elastic plate. It has been shown that using this new stress intensity factor solution it is possible to correlate fatigue crack growth data measured on surface cracked plate. Fatigue, crack growth, stress intensity factor, circumferential semi elliptical surface crack. Stressintensity factors for semielliptical surface. These four solutions can be superimposed to obtain stressintensity factor solutions for other stress distributions, such as those caused by internal pressure and by thermal shock. Stress intensity factor for a surface crack at the thread root of a pipe joint. Most practical crack con gurations are embedded and surface breaking planar cracks subjected to complex twodimensional stress elds.
It is one of the most fundamental and useful parameters in all of fracture mechanics. Stress intensity factor for a surface crack at the thread. The extended finite element method xfem alleviates these shortcomings. If the fatigue load is cyclic tension only, without bending, the crack front is perpendicular to the material surface. Abstract this paper presents an empirical stressintensity 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. The stress intensity factor is generally expressed in the form k y. These solutions have been obtained over the past 16 years using approximate analytical methods, experimental methods, and engineering estimates. Today, it is the critical stress intensity factor k ic, found in the plane strain condition, which is accepted as the defining property in linear elastic fracture mechanics. Stress intensity factors for semielliptical surface cracks in platetoplate butt welds with parallel misalignment of same thickness 1. Pdf stress intensity factor solutions for surface cracks in flat plates. This study investigates the stress intensity factor sif of. This report describes some recent efforts at improving the stress intensity factor solutions for cracks in such geometries with emphasis on hollow cylinders. Stress intensity factor of surface and interface cracks in. As the stress intensity factor reaches the k ic value, unstable fracture.
In this study, the stress intensity factors of surface cracks under two assumed residual stress fields were calculated. Recent studies have shown that the crack growth of pwscc is mainly driven by the weld residual stress wrs within the dissimilar metal weld the existing stress intensity factor k solutions for surface cracks in pipe typically require a polynomial stress distribution through the pipe wall thickness. Therefore, the purpose of this paper is to present and analyze the stress intensity factors sifs along the crack front for the sickleshaped surface crack in round bars. The stressintensity factors used to develop the equation were obtained from a previous threedimensional, finiteelement analysis of semielliptical surface cracks. In theory the stress at the crack tip where the radius is nearly zero, would tend to infinity. The solutions are categorized by the location of the crack, either embedded, in a plate surface or edge, or at a hole, in tables 11.
1391 656 522 843 1559 410 319 691 494 1178 614 124 425 539 62 664 1479 345 979 435 931 1374 806 674 822 1192 1247 1563 1136 714 258 438 1557 860 1584 1552 15 1165 280 389 169 1004 1465 851 1210 1355 68 975 933