A New Stress-Intensity Factor Solution for an External Surface Crack in Spheres

2021 ◽  
Author(s):  
James C. Sobotka ◽  
Yi-Der Lee ◽  
Joseph W. Cardinal ◽  
R. Craig McClung
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Crack Front ◽  
Surface Crack ◽  
Degrees Of Freedom ◽  
External Surface ◽  
Crack Plane ◽  
Finite Element Analyses ◽  
Stress Variations ◽  
Geometric Formulation

Abstract This paper describes a new stress-intensity factor (SIF) solution for an external surface crack in a sphere that expands capabilities previously available for this common pressure vessel geometry. The SIF solution employs the weight function (WF) methodology that enables rapid calculations of SIF values. The WF methodology determines SIF values from the nonlinear stress variations computed for the uncracked geometry, e.g., from service stresses and/or residual stresses. The current approach supports two degrees of freedom that denote the two crack tips located normal to the surface and the surface of the sphere. The geometric formulation of this solution enforces an elliptical crack front, maintains normality of the crack front with the free surface, and supports two degrees of freedom for fatigue crack growth from an internal crack tip and a surface crack tip. The new SIF solution accommodates spherical geometries with an exterior diameter greater than or equal to four times the thickness. This WF SIF solution has been combined with stress variations common for spherical pressure vessels: uniform internal pressure on the interior surface, uniform tension on the crack plane, and uniform bending on the crack plane. This paper provides a complete overview of this solution. We present for the first time the geometric formulation of the crack front that enables the new functionality and set the geometric limits of the solution, e.g., the maximum size and shape of the crack front. The paper discusses the bivariant WF formulation used to define the SIF solution and details the finite element analyses employed to calibrate terms in the WF formulation. A summary of preliminary verification efforts demonstrates the credibility of this solution against independent results from finite element analyses. We also compare results of this new solution against independent SIFs computed by finite element analyses, legacy SIF solutions, API 579, and FITNET. These comparisons indicate that the new WF solution compares favorably with results from finite element analyses. This paper summarizes ongoing efforts to improve and extend this solution, including formal verification and development of an internal surface crack model. Finally, we discuss the capabilities of this solution’s implementation in NASGRO® v10.0.

Finite Element Analyses of Modified Compact Tension Shear (MCTS)-Specimens under Mixed-Mode Loading Conditions

2010 ◽  
Vol 29-32 ◽  
pp. 1334-1338
Author(s):  
Gui Ying Qi ◽  
Qing Fen Li
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Mixed Mode ◽  
Compact Tension ◽  
Crack Plane ◽  
Initial Growth ◽  
Loading Conditions ◽  
Finite Element Analyses ◽  
Mixed Mode Loading ◽  
Inclined Crack

In this paper a detailed 3D-finite element analyses results of modified compact tension shear (MCTS)-specimens with an inclined crack plane or crack front under mixed-mode loading conditions are presented. It is found that under mixed-mode loading, a superposition of all fracture modes I, II and III can be generated along the straight crack front of MCTS-specimens, and the maximum of the total SERR along the crack front of two different MCTS-specimens is found at right hand side of crack front corner，where the risk of crack initial growth is highest. The computational fracture analysis is based on the calculation of separated energy release rates GI, GII and GIII along the crack front by the numerically highly effective modified virtual crack closure integral(MVCCI)-method.

Application of Extended Finite Element Method (XFEM) to Stress Intensity Factor Calculations

2015 ◽  
Author(s):  
Do-Jun Shim ◽  
Mohammed Uddin ◽  
Sureshkumar Kalyanam ◽  
Frederick Brust ◽  
Bruce Young
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Degrees Of Freedom ◽  
Extended Finite Element Method ◽  
Partition Of Unity ◽  
Extended Finite Element ◽  
Element Method

The extended finite element method (XFEM) is an extension of the conventional finite element method based on the concept of partition of unity. In this method, the presence of a crack is ensured by the special enriched functions in conjunction with additional degrees of freedom. This approach also removes the requirement for explicitly defining the crack front or specifying the virtual crack extension direction when evaluating the contour integral. In this paper, stress intensity factors (SIF) for various crack types in plates and pipes were calculated using the XFEM embedded in ABAQUS. These results were compared against handbook solutions, results from conventional finite element method, and results obtained from finite element alternating method (FEAM). Based on these results, applicability of the ABAQUS XFEM to stress intensity factor calculations was investigated. Discussions are provided on the advantages and limitations of the XFEM.

Reliability of Welded Structures Containing Cracks in Heat-Affected Zones

2000 ◽  
Vol 122 (4) ◽  
pp. 225-232 ◽  
Author(s):  
David B. Lanning ◽  
M.-H. Herman Shen
Keyword(s):  
Fracture Toughness ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Crack Front ◽  
Surface Crack ◽  
Material Properties ◽  
Coarse Grained ◽  
Welded Structures ◽  
Weakest Link ◽  
Link Model

This study investigates the reliability of a plate containing a semi-elliptical surface crack intersecting regions of dissimilar material properties. A weakest-link model is developed to express fracture toughness distributions in terms of effective crack lengths that account for the varying stress intensity factor along the crack front. The model is intended to aid in the development of fracture toughness distributions for cracks encountering local brittle zones (LBZ) in the heat-affected zones (HAZ) of welded joints, where lower-bound fracture toughness values have been measured in the laboratory when a significant portion of the crack front is intersecting the coarse-grained LBZs. An example reliability analysis is presented for a surface crack in a material containing alternating bands of two Weibull-distributed toughnesses. [S0892-7219(00)01203-6]

Finite Element Fracture Mechanics Study of Pre-Northridge Connections

2006 ◽  
Vol 324-325 ◽  
pp. 1007-1010 ◽  
Author(s):  
Hong Bo Liu ◽  
Chang Hai Zhai ◽  
Yong Song Shao ◽  
Li Li Xie
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Behavior ◽  
Integral Approach ◽  
J Integral ◽  
Finite Element Analyses ◽  
Element Analysis ◽  
Weld Root

The objective was to quantify the variation of stress intensity factor to weld root flaw sizes in steel frame connections. Finite-element analyses were used to study fracture toughness in welded beam-column connections. Investigations of fracture behavior mainly focused on the standard pre-Northridge connection geometry. Finite element analysis was performed using the ANSYS computer program. Stress intensity factor was calculated through a J-integral approach. Results show that stress intensity factor is not uniform and is largest in the middle of beam flange. Stress intensity factor increases nearly linear with the increase of flaw size. Backing bars have little effect on weld fractures.

Finite Element Analysis of Polyethylene Pipe Butt Fusion Joints with Circumferential Surface Cracks

2013 ◽  
Vol 785-786 ◽  
pp. 1151-1158
Author(s):  
Zhi Bin Zhu ◽  
Xiao Xiang Yang ◽  
Li Jing Chen ◽  
Nai Chang Lin ◽  
Zhi Tuo Wang ◽  
...  
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Viscoelastic Material ◽  
Surface Crack ◽  
Crack Depth ◽  
Surface Cracks ◽  
Element Analysis ◽  
Polyethylene Pipe

Based on the viscoelastic material property of polyethylene pipe, software ANSYS was used to simulate and analyze the mechanical property of polyethylene pipe butt fusion joints with circumferential surface crack defects. The viscoelastic material creep parameters were characterized as Prony series and 1/4 node singular element was selected for meshing along the boundaries of the crack, then the stress intensity factor of polyethylene pipe butt fusion joints with circumferential surface crack was calculated under the uniform internal pressure. Through the finite element simulation, the result showed that polyethylene pipe were most likely to fracture failure when crack initiated. Thus the viscoelasticity of materials can be ignored when analyzing the stress intensity factor of circumferential surface cracks of polyethylene pipe. the main influencing factor of the circumferential crack defects was the ratio of the crack depth to the thickness of polyethylene pipe.

Failure Assessment Diagrams of Semi-Elliptical Surface Crack with Constraint Effect

2007 ◽  
Vol 353-358 ◽  
pp. 1952-1955
Author(s):  
Hyung Yil Lee ◽  
Jin Haeng Lee ◽  
Tae Hyung Kim
Keyword(s):  
Finite Element ◽  
Finite Element Modeling ◽  
Surface Crack ◽  
J Integral ◽  
Finite Element Analyses ◽  
Constraint Effect ◽  
Failure Assessment ◽  
T Stress ◽  
Cracked Structures ◽  
Constraint Effects

For accurate failure assessment, a second parameter like T-stress describing the constraint is needed in addition to the single parameter J-integral. In this work, selecting the structures of surface-cracked plate and pipe, we perform line-spring finite element modeling, and accompanying elastic-plastic finite element analyses. We then present a framework, which includes the constraint effects in the R6 FAD approach for failure assessment of cracked-structures.

Construction of a Dynamic Weight Function From a Finite-Element Solution for a Cracked Beam

1980 ◽  
Vol 47 (1) ◽  
pp. 51-56 ◽  
Author(s):  
H. J. Petroski ◽  
J. L. Glazik ◽  
J. D. Achenbach
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Weight Function ◽  
Crack Plane ◽  
Cracked Beam ◽  
Crack Face ◽  
Dynamic Weight ◽  
Dynamic Loadings

An elastodynamic weight function for a cracked beam is shown to be determined by the elastodynamic stress intensity factor corresponding to a single crack-face loading of the beam. This weight function suffices to determine the time-dependent stress intensity factor corresponding to other dynamic loadings of the same cracked beam. The example of a center-cracked pinned-pinned beam serves to illustrate and verify the technique. The weight function is constructed from finite element results for the case of a step pressure distributed uniformly along the beam, and the case of a step load concentrated at the crack plane serves as an illustration of the efficacy of the weight function so constructed.

Computational Fracture Analyses of a Compact Tension Shear (CTS) Specimen with an Inclined Crack Plane

2008 ◽  
Vol 385-387 ◽  
pp. 741-744 ◽  
Author(s):  
Qing Fen Li ◽  
Gui Ying Qi ◽  
Sheng Yuan Yan ◽  
Friedrich G. Buchholz
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Compact Tension ◽  
Shear Loading ◽  
Crack Plane ◽  
Inclined Crack ◽  
Fe Modelling ◽  
Straight Crack ◽  
Energy Release Rates ◽  
Tension Loading

In this paper some results of 3D-finite element analyses of a modified CTS-specimen with an inclined crack plane are presented. It will be shown, that through the inclination of the crack plane, even under pure tension loading of the specimen, a superposition of all fracture modes I, II and III can be generated along the straight crack front of the inclined crack plane. Furthermore, mixed-mode I, II and III loading conditions can also be generated if this modified CTS-specimen is subject to an in-plane tension/shear loading. The computational fracture analysis is based on the calculation of separated energy release rates GI, GII and GIII along the crack front by the numerically highly effective modified virtual crack closure integral(MVCCI)-method and for the finite element(FE)-modelling the commercially available FE-code ANSYS is utilized.

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