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

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.

2014 ◽  
Vol 136 (4) ◽  
Author(s):  
F. Benyahia ◽  
A. Albedah ◽  
B. Bachir Bouiadjra

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.


Author(s):  
Masayuki Arai

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.


Author(s):  
Yifan Huang ◽  
Xinjian Duan

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.


2017 ◽  
Vol 52 (8) ◽  
pp. 1113-1120 ◽  
Author(s):  
Inés Iváñez ◽  
Matías Braun

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.


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