A computational tool for estimating stress fields along a surface crack front

2014 ◽  
Vol 38 (2) ◽  
pp. 180-189 ◽  
Author(s):  
A. S. Chernyatin ◽  
Y. G. Matvienko ◽  
I. A. Razumovsky
Keyword(s):  
Crack Front ◽  
Surface Crack ◽  
Stress Fields ◽  
Computational Tool

scholarly journals Combining experimental and numerical analysis to estimate stress fields along the surface crack front

2013 ◽  
Vol 7 (25) ◽  
pp. 15-19 ◽  
Author(s):  
A.S. Chernyatin ◽  
Yu.G. Matvienko ◽  
I.A. Razumovsky
Keyword(s):  
Numerical Analysis ◽  
Crack Front ◽  
Surface Crack ◽  
Stress Fields

scholarly journals Universal characterization of three-dimensional creeping crack-front stress fields

2018 ◽  
Vol 152-153 ◽  
pp. 104-117 ◽  
Author(s):  
Wanlin Guo ◽  
Zhiyuan Chen ◽  
Chongmin She
Keyword(s):  
Crack Front ◽  
Three Dimensional ◽  
Stress Fields

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.

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]

Closure Effect on Interaction of Two Surface Cracks Under Cyclic Bending

2010 ◽  
Author(s):  
Masanori Kikuchi ◽  
Yoshitaka Wada ◽  
Maigefeireti Maitireyimu ◽  
Hirotaka Sano
Keyword(s):  
Crack Growth ◽  
Crack Closure ◽  
Crack Front ◽  
Surface Crack ◽  
Specimen Surface ◽  
Surface Cracks ◽  
Paris Law ◽  
C Value ◽  
Closure Effect ◽  
Surface Crack Growth

Crack closure effect on interaction of two surface crack growth processes by fatigue is studied. At first, change of C value in Paris’ law along crack front of single surface crack is measured experimentally. It is shown that C value decreases near specimen surface. Crack closure effect is studied numerically for a surface crack by elastic-plastic cyclic analyses. It is found that closure effect appears more strongly near specimen surface than the maximum-depth point. By determining effective stress intensity factor including closure effect, it is shown that change of C value is equal to the change of closure effect along crack front. Using new C value considering closure effect, fatigue crack growth is predicted using S-FEM. It is shown that fatigue life and crack configuration agree well with experimental ones. Finally, interaction of two surface cracks is evaluated numerically, and it is shown that crack closure plays important role on the interaction of two cracks.

Residual Stress Effects on the Crack-Front Constraints for Surface Cracks in Pipes

2010 ◽  
Author(s):  
Xudong Qian ◽  
Tieping Li
Keyword(s):  
Residual Stress ◽  
Residual Stresses ◽  
Wall Thickness ◽  
Crack Front ◽  
Heat Input ◽  
Crack Depth ◽  
Geometric Parameters ◽  
Stress Fields ◽  
Surface Cracks ◽  
Linear Elastic

This paper investigates the effect of residual stresses on the linear-elastic KI-T fields along the front of circumferential surface cracks in pipelines. The numerical procedure simulates three typical patterns of residual stresses through a modified eigenstrain approach, which combines a thermal loading with a mechanical traction imposed on the heat-affected zone. The three residual stress profiles considered correspond to the high-heat input, the medium-heat input and the low heat input welding processes for circumferential butt welds in pipes outlined in BS 7910. The linear-elastic KI-T stresses, computed from the interaction-integral approach, characterize the constraints along the front of the circumferential flaw. The numerical investigation, covering a comprehensive matrix of geometric parameters, shows that different residual stress fields impose substantial effects on the KI-T stresses along the front of the surface crack in the wall of a pipeline. The deepest point along the crack-front often experiences low crack-front constraints characterized by the computed negative T-stresses for all three residual stress fields considered. The magnitudes of the KI-values and T-stresses show pronounced variations with the change in the ratio of the crack depth over the wall thickness of the pipe (a/t). The variation in the crack aspect ratio (the crack depth over the crack length, a/c) introduces marginal variation in the computed T stresses. The ratio of the outer diameter to the wall thickness of pipe imposes very little effect on the linear-elastic crack-front constraints for the geometric parameters considered.

Nonidealized Surface to Through-Wall Crack Transition Model for Axial Cracks in Cylinders

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Do-Jun Shim ◽  
Jeong-Soon Park ◽  
David Rudland
Keyword(s):  
Crack Front ◽  
Surface Crack ◽  
Crack Opening ◽  
Crack Depth ◽  
Outer Diameter ◽  
Transition Model ◽  
Opening Displacement ◽  
Proposed Model ◽  
Primary Water ◽  
Crack Transition

Recent studies have shown that a subcritical surface crack, due to primary water stress corrosion cracking (PWSCC), can transition to a through-wall crack (TWC) with significant differences between the inner diameter (ID) and outer diameter (OD) crack lengths. This behavior has been observed for both circumferential and axial cracks. Recently, a surface to TWC transition model has been developed for circumferential cracks using existing K and COD (crack opening displacement) solutions for nonidealized circumferential TWCs. In this paper, a similar crack transition model (CTM) was developed for axial cracks. As a first step, a study was conducted to define the appropriate crack front shape for nonidealized axial TWCs. Then, elastic finite element analyses were carried out to develop K and COD solutions using these crack front shapes. The newly developed solutions were utilized for the CTM. The present CTM includes a criterion for transitioning the final surface crack to the initial nonidealized TWC. This criterion determines when the transition should occur (based on surface crack depth) and determines the two crack lengths (at ID and OD surfaces) of the initial nonidealized TWC. Furthermore, nonidealized TWC growth calculation can be conducted using the proposed model. Example results (crack length and COD) obtained from the proposed model were compared to those obtained from the natural crack growth simulations. Results presented in this paper demonstrated the applicability of the proposed model for simulating axial crack transition.

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