Application of Surface Crack Analysis System ‘SCAN’ to Cracks at Hole

2002 ◽  
Author(s):  
Nagatoshi Seki ◽  
Masaki Shiratori ◽  
Toshiro Miyoshi ◽  
Youichi Yamashita ◽  
Kenji Sakano
Keyword(s):  
Surface Crack ◽  
Notch Root ◽  
Fem Analysis ◽  
Radius Of Curvature ◽  
Surface Cracks ◽  
Finite Element Analyses ◽  
Influence Function Method ◽  
Influence Coefficients ◽  
Enormous Amount ◽  
Analysis System

The authors have proposed an influence function method by which stress intensity factor, K, of surface cracks can be calculated easily for arbitrarily distributed surface stresses. They have developed the database of influence coefficients, Kij, for various types of surface cracks through a series of finite element analyses. And they also have developed a software system “SCAN”, based upon the above developed database, by which K-values of surface cracks can be evaluated promptly, and further, fatigue crack propagation can be simulated easily by a personal computer. In this paper the authors have studied how they can apply the SCAN system to the problem of the surface cracks initiated from the edge of a circular hole of a rectangular plate. Since circular notches have various radiuses of curvature, the concentrated stress distribution at the notch root is different depending upon the radius of curvature. Therefore, strictly speaking, K-values have to be evaluated for each case, one by one, which means enormous amount of FEM analysis are necessary. But the authors have found that the database of a surface crack in a flat plate already installed in the SCAN system can be applied to this problem with satisfactory accuracy, which means the K-values of this problem can be evaluated promptly by the SCAN system.

Prediction of Fatigue Crack Propagation of Sub-Surface Cracks by “SCAN”

2004 ◽  
Author(s):  
Masaki Shiratori ◽  
Naoki Yoshikawa ◽  
Fuminori Iwamatsu ◽  
Hisao Matsushita ◽  
Shigeo Omata ◽  
...  
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Crack ◽  
Influence Function ◽  
Surface Cracks ◽  
Finite Element Analyses ◽  
Influence Function Method ◽  
Influence Coefficients ◽  
Asme Code

The authors have proposed an influence function method by which stress intensity factor, K, of surface cracks can be calculated easily for arbitrarily distributed surface stresses. They have developed the database of influence coefficients, Kij, for various types of surface cracks through a series of finite element analyses [1]. And they also have developed a software system “SCAN”, based upon the above developed database, by which K-values of surface cracks can be evaluated promptly, and further, fatigue crack propagation can be simulated easily by a personal computer. In this paper the authors have studied how they can apply the SCAN system to the problem of the sub-surface cracks. They have developed “SCAN Sub-Surface Crack Version”, where SCAN is improved by newly analyzed influence coefficients for a series of sub-surface cracks, and by following the scenario described in ASME CODE, SECTION XI [2]. They have found that the database of a surface crack in a flat plate already installed in the SCAN system, with the above described Kij database for sub-surface cracks, can be applied to this problem with satisfactory accuracy, which means the K-values of this problem can be evaluated promptly by the SCAN system, and the propagation of small sub-surface cracks can be simulated easily.

Estimation of Fatigue Crack Propagation of Subsurface Cracks by “SCAN”

2006 ◽  
Author(s):  
Shin Nakanishi ◽  
Fuminori Iwamatsu ◽  
Masaki Shiratori ◽  
Hisao Matsushita
Keyword(s):  
Fatigue Crack ◽  
Fatigue Life ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Surface Crack ◽  
Surface Cracks ◽  
Subsurface Crack ◽  
Subsurface Cracks ◽  
Influence Coefficients ◽  
Asme Code

The authors have proposed an influence function method to calculate stress intensity factor, K, of the surface cracks. This method makes the calculating task easier for arbitrarily distributed surface stresses. They have developed the database of influence coefficients, Kij, for various types of surface cracks through a series of finite element analyses.[1] They also have developed a software system “SCAN” (Surface Crack Analysis), from the database. The K values of surface cracks can be evaluated immediately, and further, fatigue crack propagation can be simulated easily with a personal computer. A fatigue crack often initiates from a defect located at the subsurface of a structural member. In this case, it is important to account for the fatigue life from the initiation of a subsurface crack to its propagation into a surface crack. However, since it is difficult to simulate this process precisely, the authors have proposed a simple model about the transition from a subsurface crack into a surface crack based upon ASME CODE SECTION XI [2] and WES 2805 STANDARD. [3] They have developed a SCAN system – Subsurface Crack Version-. They calculated the fatigue life for some models of subsurface cracks and compared the quantitative differences between two standards.

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.

Predicting the Brittle-to-Ductile Transition Temperatures for Surface Cracks in Pipeline Girth Welds: It’s Better Than You Thought

2008 ◽  
Author(s):  
Gery Wilkowski ◽  
David Rudland ◽  
Do-Jun Shim ◽  
David Horsley
Keyword(s):  
Transition Temperature ◽  
Surface Crack ◽  
Master Curve ◽  
Crack Depth ◽  
Temperature Shift ◽  
Transition Temperatures ◽  
Surface Cracks ◽  
Line Pipe ◽  
Brittle To Ductile Transition ◽  
Girth Welds

A methodology to predict the brittle-to-ductile transition temperature for sharp or blunt surface-breaking defects in base metals was developed and presented at IPC 2006. The method involved applying a series of transition temperature shifts due to loading rate, thickness, and constraint differences between bending versus tension loading, as well as a function of surface-crack depth. The result was a master curve of transition temperatures that could predict dynamic or static transition temperatures of through-wall cracks or surface cracks in pipes. The surface-crack brittle-to-ductile transition temperature could be predicted from either Charpy or CTOD bend-bar specimen transition temperature information. The surface crack in the pipe has much lower crack-tip constraint, and therefore a much lower brittle-to-ductile transition temperature than either the Charpy or CTOD bend-bar specimen transition temperature. This paper extends the prior work by presenting past and recent data on cracks in line-pipe girth welds. The data developed for one X100 weld metal shows that the same base-metal master curve for transition temperatures works well for line-pipe girth welds. The experimental results show that the transition temperature shift for the surface-crack constraint condition in the weld was about 30C lower than the transition temperature from standard CTOD bend-bar tests, and that transition temperature difference was predicted well. Hence surface cracks in girth welds may exhibit higher fracture resistance in full-scale behavior than might be predicted from CTOD bend-bar specimen testing. These limited tests show that with additional validation efforts the FITT Master Curve is appropriate for implementation to codes and standards for girth-weld defect stress-based criteria. For strain-based criteria or leak-before-break behavior, the pipeline would have to operate at some additional temperature above the FITT of the surface crack to ensure sufficient ductile fracture behavior.

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