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Finite element analysis (FEA) has been undertaken to calculate the stress intensity factor (K) of cracks emerging from a corrosion pit in a martensitic stainless steel cylinder stressed remotely. The corrosion pit was in the form of a truncated spheroid with depth equal to the full mouth opening. This geometry reflects the configuration found in laboratory testing and in service in low chloride solution, albeit the pit is considered ideally smooth. The pit depth was fixed at 150 µm. A semi-circular crack was adopted with depths ranging from 25 µm to 250 µm. Computations were performed assuming purely elastic condition in most cases but the impact of plasticity around the pit was evaluated for selected crack depths. A key observation of this investigation is that cracks on either side of the pit that are small compared to the pit depth act independently with K values unaffected by the presence of the other crack. However, as the cracks on either side of the pit grow to a depth approaching the pit depth the K value is mutually increased. For cracks with depth close to that of the pit depth the stress intensity factor is increased due to the presence of the pit such that the expected increase of K with increasing crack size does not immediately materialise due to the decreasing stress gradient away from the pit. Elastic plastic analysis in discreet cases confirms these trends but highlights the need to avoid simple comparison of K values that may not be applicable because of plasticity around the pit.
Stress intensity factors for cracks in grooved rolls used for hot-rolling
Stress intensity factors for cracks in grooved rolls used for hot-rolling
57Weight functions and stress intensity factors for internal surface semi-elliptical crack in thick-walled cylinder
Weight functions and stress intensity factors for internal surface semi-elliptical crack in thick-walled cylinder
11On the calculation of stress intensity factors for surface cracks in welded pipe–plate and tubular joints
On the calculation of stress intensity factors for surface cracks in welded pipe–plate and tubular joints
88Effect of residual stress around cold worked holes on fracture under superimposed mechanical load
Effect of residual stress around cold worked holes on fracture under superimposed mechanical load
38Calculation of stress intensity factors for interlaminar cracks in composite laminates
Calculation of stress intensity factors for interlaminar cracks in composite laminates
3Simple Stress Substitution Approach for Computation of Stress Intensity Factors of Face-Loaded Cracks
The accurate computation of stress intensity factors (SIFs) of face-loaded cracks is of significant importance for engineering practices. Based on the analytical stress field of a central c...
Read more219Rapid Calculation of Stress Intensity Factors
A method for computing stress intensity factors for cracks embedded in structural details is described. It consists of adding to accepted solutions for cracks in finite plates and bodies of uniform contour a geometry correction factor which accounts for the stress gradient produced by the geometric discontinuity of the detail. This correction factor is determined by integrating away the stresses normal to the line where the crack is to be inserted. The method is applied to the case of a crack emanating from a circular hole in a plate, and the results are found to be in good agreement with Bowie's numerical solution. Values of the stress intensity factor for cracks emanating from spherical weld porosities, and part-through cracks at stiffeners and cover plate ends are computed.
Read more10Size effects on spheroidal voids by Finite Fracture Mechanics and application to corrosion pits
The present work aims at investigating the failure size effect of a spheroidal void in an infinite linear elastic solid under remote tension by means of the coupled Finite Fracture Mechanics (FFM) approach. The opening stress field and the stress intensity factor (SIF) of an annular crack surrounding the cavity —necessary for the FFM implementation— are obtained numerically through parametric axisymmetric finite element analyses (FEAs): The spheroid aspect ratio is varied between 0.1 and 10 and Poisson's ratio between 0.1 and 0.5. Accordingly, semi‐analytical functions approximating the stress concentration factor and the SIF are put forward. Finally, the failure size effect on spheroidal voids is reported, and FFM predictions are compared with experimental results on the fatigue limit arising from corrosion pits, showing a fairly good agreement.
Read more2Calculation of Stress Intensity Factors for Elliptical Cracks in Finite Bodies by Using the Boundary Weight Function Method
In this study, mode I stress intensity factors for a three-dimensional finite cracked body with arbitrary shape and subjected to arbitrary loading is presented by using the boundary weight function method. The weight function is a universal function for a given cracked body and can be obtained from any arbitrary loading system. A numerical finite element method for the determination of weight function relevant to cracked bodies with finite dimensions is used. Explicit boundary weight functions are successfully demonstrated by using the least-squares fitting procedure for elliptical quarter-corner crack and embedded elliptical crack in parallelepipedic finite bodies. If the stress distribution of a cut-out parallelepipedic cracked body from any arbitrary shape of cracked body subjected to arbitrary loading is determined, the mode I stress intensity factors for the cracked body can be obtained from the predetermined boundary weight functions by a simple surface integration. Comparison of the calculated results with some available solutions in the published literature confirms the efficiency and accuracy of the proposed boundary weight function method.
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4Analysis of the stress intensity factor of welded joints under prior corrosion and complex stress fields
Taking cruciform welded joints under different corrosion degrees, together with 45° inclined angle and full penetration load-carrying fillet, as the research object, the stress intensity factor of a quarter-circular corner crack of welded joints is calculated based on FRANC3D with ABAQUS. Effects of different corrosion pit sizes, crack aspect ratios, and crack depths on stress intensity factor are analyzed. The results show that pit depth plays a major role in stress intensity factor, while the effect of pit radius is relatively small. The cracking modes of the surface and the deepest point are mode I, and mixed modes I and II, respectively. Effects of pit depths, crack aspect ratios, and crack depths on the stress intensity factor at the surface point are greater than at the deepest point.
Read more10Stress Intensity Factor Solution for Subsurface Flaw Estimated by Influence Function Method
The flaw evaluation procedure in ASME Boiler and Pressure Vessel Code Section XI Appendix A is based on the linear elastic fracture mechanics, where the stress intensity factor for the given flaw geometry and applied stress is used to evaluate fatigue crack growth and unstable brittle fracture. The current original procedure for calculation of stress intensity factor for elliptical subsurface crack was based on a linearization method to have conservative estimation for nonlinear stress fields. To improve this current approach, the stress intensity factor solution for subsurface flaw was discussed to allow for the stress variation at the crack location to be represented by a forth order polynomial function. The use of a forth order polynomial fit to represent the actual stress distribution will greatly improve the accuracy of the method for nonlinear stress fields such as those caused by thermal transient loadings and residual stresses caused by weld. The coefficients of stress intensity factor for elliptical subsurface flaw for polynomial fit were estimated by the influence function method. These coefficients were verified by the comparison of stress intensity factor calculated by other similar solutions.
Read more32Computation of stress intensity factors for interfacial cracks
Computation of stress intensity factors for interfacial cracks
72Computation of Mixed-Mode Stress Intensity Factors for Cracks in Three-Dimensional Functionally Graded Solids
This work applies a two-state interaction integral to obtain stress intensity factors along cracks in three-dimensional functionally graded materials. The procedures are applicable to planar cracks with curved fronts under mechanical loading, including crack-face tractions. Interaction-integral terms necessary to capture the effects of material nonhomogeneity are identical in form to terms that arise due to crack-front curvature. A discussion reviews the origin and effects of these terms, and an approximate interaction-integral expression that omits terms arising due to curvature is used in this work to compute stress intensity factors. The selection of terms is driven by requirements imposed by material nonhomogeneity in conjunction with appropriate mesh discretization along the crack front. Aspects of the numerical implementation with (isoparametric) graded finite elements are addressed, and examples demonstrate the accuracy of the proposed method.
Read more20Computations of stress intensity factors for semi-elliptical cracks with high aspect ratios by using the tetrahedral finite element (fully automated parametric study)
Computations of stress intensity factors for semi-elliptical cracks with high aspect ratios by using the tetrahedral finite element (fully automated parametric study)
Read more가중함수법에 의한 볼트 체결부 균열의 임계 경사각 결정에 관한 연구
Mechanical joints such as bolted or riveted joints are widely used in mechanical components. The reliable determination of the stress intensity factors for cracks in bolted joints is needed to evaluate the safety and fatigue life of them. The weight function method is an efficient technique to calculate the stress intensity factors for various loading conditions because only the stress analysis of an uncracked model is required. In this paper the mixed-mode stress intensity factors for cracks in bolted joints are obtained by weight function method, in which the coefficients of weight function are determined by finite element analyses for reference loadings. Critical inclined angle that mode I stress intensity factor becomes maximum is determined and the effects of crack length and the magnitude of clearance on critical inclined angle are investigated.
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