Stress Intensity Factor and Crack Opening Area of Circumferentially-Cracked Pipe Under Torsion Moment

2020 ◽  
Author(s):  
Yifan Huang ◽  
Xinjian Duan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Opening ◽  
Three Dimensional ◽  
Bending Moment ◽  
Torsion Moment ◽  
Dimensional Finite Element ◽  
3D Fea ◽  
Three Dimensional Finite Element

Abstract The deterministic leak-before-break (LBB) analysis and probabilistic fracture mechanics (PFM) assessment are two primary approaches for demonstrating extremely low probability of rupture of pressurized piping in the nuclear energy industry. Both stress intensity factor (SIF) and crack opening area (COA) are key components to the LBB and PFM assessments. Most of the studies and engineering practices focus on the SIF and COA due to axial tension, bending moment and internal pressure while limited investigations target on these parameters caused by torsion moment. The objective of this study is to perform three-dimensional finite element analyses (3D FEA) to determine both SIF and COA for through-wall circumferential cracks in the pipe under bending or torsion moment. A range of normalized crack lengths (i.e. θ/π = 1/18 to 4/9) and three pipe radius over thickness ratios (i.e. Rm/t = 5, 10 and 25) are considered. Empirical solutions of the SIF for torsion loading as functions of crack geometry are developed. Comparisons for SIF regarding combined bending and torsion moments evaluated using code-specified solutions are presented. Finally, the COAs regarding the two loading modes are discussed. Such study is expected to be useful for both deterministic LBB analysis and PFM assessment of pressurized pipes.

Stress Intensity Factor for Repaired Circumferential Cracks in Pipe With Bonded Composite Wrap

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Benyahia ◽  
A. Albedah ◽  
B. Bachir Bouiadjra
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Fracture Criterion ◽  
Three Dimensional ◽  
Element Analysis ◽  
Composite Systems ◽  
Bonded Composite ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The use of composite systems as a repair methodology in the pipeline industry has grown in recent years. In this study, the analysis of the behavior of circumferential through cracks in repaired pipe with bonded composite wrap subjected to internal pressure is performed using three-dimensional finite element analysis. The fracture criterion used in the analysis is the stress intensity factor (SIF). The obtained results show that the bonded composite repair reduces significantly the stress intensity factor at the tip of repaired cracks in the steel pipe, which can improve the residual lifespan of the pipe.

Stress Intensity Factor of an Elliptical Crack With a Wavy Crack Front

2016 ◽  
Author(s):  
Masayuki Arai
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Front ◽  
Perturbation Technique ◽  
Three Dimensional ◽  
Elastic Field ◽  
Element Analysis ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

In this paper, the stress intensity factor KI for the crack front line a − ε(1 + cosmθ), which is slightly perturbed from a complete circular line with a radius of a, is determined. The method used in this study is based upon the perturbation technique developed by Rice for solving the elastic field of a crack whose front slightly deviates from some reference geometry. It is finally shown that the solution for the stress intensity factor matches the results of a three-dimensional finite element analysis.

Three-dimensional Finite Element Analysis of a Semi-Elliptical Circumferential Surface Crack in a Carbon Steel Pipe Subjected to a Bending Moment

2005 ◽  
Vol 40 (6) ◽  
pp. 525-533 ◽  
Author(s):  
S. A Ligoria ◽  
G. M. S Knight ◽  
D. S Ramachandra Murthy
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Fatigue Life ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Surface Crack ◽  
Three Dimensional ◽  
Experimental Results ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element

The study of crack growth is important to evaluate the structural integrity of nuclear power plant piping from the viewpoint of the leak-before-break concept. A thick-walled pipe with a semi-elliptical circumferential surface crack of different initial crack sizes subjected to a bending load is considered for the analysis. A three-dimensional finite element code using ANSYS (Version 8) has been developed with the capability to handle singularity and to evaluate the mode I stress intensity factor based (SIF) on the displacement extrapolation method. The crack growth rate has been calculated by applying the Paris law. The fatigue life predicted for crack penetration through the wall thickness has been compared with that of experimental results in published literature. The deviation is found to be within 17 per cent. Using the finite element model, data in respect of the stress intensity factor for different stresses, thicknesses, crack depths, and half-crack-length conditions have been predicted. Based on the data, a new correlation has been evolved to evaluate the stress intensity factor range in the depth and surface directions. The stress intensity factor has also been calculated by the empirical relations given in the ASM Handbook. The predicted fatigue life using the plate equation deviates from experimental results by a maximum of 77 per cent while the deviation of the prediction using the pipe equation is more than 100 per cent in many cases. The predictions with the proposed correlation give better results that fall within 21 per cent deviation from the experimental results.

scholarly journals Numerical analysis of surface cracks repaired with single and double patches of composites

2017 ◽  
Vol 52 (8) ◽  
pp. 1113-1120 ◽  
Author(s):  
Inés Iváñez ◽  
Matías Braun
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Depth ◽  
Three Dimensional ◽  
Composite Patch ◽  
Dimensional Finite Element ◽  
Patch Repairs ◽  
Maximum Stress Intensity ◽  
Three Dimensional Finite Element

In this work, the performances of circular single- and double-sided composite patch repairs are compared by computing the maximum stress intensity factor of a repaired surface crack. The three-dimensional finite-element method is used to calculate the stress intensity factor along the crack. The effects of the crack depth, composite patch thickness and patch material on the stress intensity factor variation are highlighted. The obtained results show that the selection of single- or double-sided patches depends on both the crack depth and patch thickness.

The Effect of Flaw Shape on the Fracture Propensity of Nozzle Corner Flaws

1988 ◽  
Vol 110 (1) ◽  
pp. 59-63 ◽  
Author(s):  
E. Friedman ◽  
D. P. Jones
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Growth ◽  
Three Dimensional ◽  
Stable Crack Growth ◽  
Asme Code ◽  
Simplified Procedure ◽  
Three Dimensional Finite Element ◽  
Flaw Shape

Three-dimensional finite element models were formulated to evaluate the distribution of the elastic stress intensity factor around the periphery of cracklike flaws postulated to exist at the corners of nozzles intersecting cylindrical shells. The effect of the assumed shape of the nozzle corner flaw on the distribution of the stress intensity factor along the crack front was determined in order to indicate where initiation of crack growth is most likely to occur and what shape the crack is most likely to take subsequent to stable crack growth. This is important because of the uncertainty associated with the flaw shape and its effect on crack growth in the nozzle corner region. Stress intensity factors computed from the nozzle corner flaw models were also compared with solutions evaluated using 1) a simplified procedure similar to that given in Section XI of the ASME Boiler and Pressure Vessel Code that makes use of the stresses calculated in the absence of the flaw, 2) the method recommended specifically for nozzle corner flaws in Section III of the ASME Code, and 3) a previously published empirical formula. The results of this paper confirm the adequacy of the simplified procedure for the analysis of nozzle corner flaws of different shapes.

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