Stress Intensity Factors for Internal Straight and Curved-Fronted Cracks in Thick Cylinders

2006 ◽  
Vol 128 (2) ◽  
pp. 227-232 ◽  
Author(s):  
Anthony P. Parker ◽  
Choon-Lai Tan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Surface Crack ◽  
Pressure Vessel ◽  
Worked Examples ◽  
Covering Radius ◽  
Intensity Factors ◽  
Thick Cylinder ◽  
Leak Before Break

Fatigue and leak-before-break calculations for a pressure vessel require knowledge of the stress intensity factor at the deepest point of a straight- or curved-fronted (semi-elliptical) surface crack emanating from the bore of an internally pressurized, autofrettaged thick cylinder. A limited number of available solutions is curve fitted. The concept of a tube equivalent plate (TEP), which exhibits crack-constraint characteristics matching those of a thick cylinder, is developed, and the resulting equations are curve fitted. Ratios of the TEP stress intensity factor results are then used to interpolate between certain existing solutions. This provides wide-ranging solutions covering radius ratios from 1.8 to 3.0, autofrettage overstrain from 0 to 100% and crack shapes from straight fronted to semi-circular. The calculation procedure is described using worked examples.

scholarly journals Calculation of Outer Crack Stress Intensity Factors for Nozzle Junctions in Cylindrical Pressure Vessels Using FCPAS

2021 ◽  
Author(s):  
Murat Bozkurt ◽  
David Nash ◽  
Asraf Uzzaman
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Pressure Vessel ◽  
Pressure Vessels ◽  
Stress System ◽  
Parameter Study ◽  
Intensity Factors

Abstract Pressure vessels can be subjected to various external local forces and moments acting in combination with main internal pressure. As a result of the stress system set up, and in the presence of attachment welds, surface cracks can occur on the interior and exterior walls. If these cracks cannot be detected at an early stage, there is a real potential for the vessel to rupture with obvious dangerous consequences. The behavior of fractured or geometric discontinuity structures can be investigated with linear elastic fracture mechanics (LEFM) parameters. The stress intensity factor (SIF) is the leading one, and with correct calculations, it can produce the stress intensity in the crack tip region. In cylinder-cylinder intersections subject to local loads, the maximum stress distribution occurs in and around these opening areas and failure in the system usually occurs in this region. Using this approach, the present study develops three-dimensional mixed mode stress intensity factor solutions on for external cracks on nozzle joints in cylindrical pressure vessels nozzle junctions for a variety of geometrical configurations. This was undertaken using a finite element approach and employing a bespoke software tool and solver, FCPAS - Fracture and Crack Propagation Analysis System — to create the finite element mesh and propagation characteristics. From this, a parameter study examining the influence of the crack shape, size and position was carried out with a fixed pressure vessel nozzle cylinder intersection geometry configuration and the appropriate stress intensity factors identified and reported. The FCPAS tool is shown to be an effective approach to modelling and characterizing cracks in pressure vessel nozzles.

Stress Intensity Factors for Complex-Cracked Pipes Based on Elastic Finite Element Analyses

2015 ◽  
Author(s):  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Intensity Factors ◽  
Integrity Assessment ◽  
Complex Crack ◽  
Leak Before Break

A complex crack is one of severe crack that can occur at the dissimilar metal weld of nuclear piping. A relevant fracture mechanics assessment for a pipe with a complex crack has become interested in structural integrity of nuclear piping. A stress intensity factor is not only an important parameter in the linear elastic fracture mechanics to predict the stress state at the crack tip, but also one of variables to calculate the J-integral in the elastic plastic fracture mechanics. The accurate calculation of stress intensity factor is required for integrity assessment of nuclear piping system based on Leak-Before-Break concept. In the present paper, stress intensity factors of complex-cracked pipes were calculated by using detailed 3-dimensional finite element analysis. As loading conditions, global bending, axial tension and internal pressure were considered. Based on the present FE works, the values of shape factors for stress intensity factor of complex-cracked pipes are suggested according to a variables change of complex crack geometries and pipes size. Furthermore, the closed-form expressions based on correction factor are newly suggested as a function of geometric variables. These new solutions can be used to Leak-Before-Break evaluation for complex-cracked pipes in the step of elastic J calculation.

Numerical Study on 3D Surface Crack Growth

2011 ◽  
Vol 90-93 ◽  
pp. 744-747
Author(s):  
Ming Tian Li ◽  
Shu Cai Li ◽  
Jun Lian He
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Inclination Angle ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Orientation Angle ◽  
Intensity Factors ◽  
Mode Stress ◽  
Surface Crack Growth

The inclined surface cracks are under the mixed mode I，II，III loading conditions. In order to study the surface crack growth the stress intensity factors of the front of half-circular surface crack are calculated according to fracture analysis code-3D(FRANC3D). And the influences of inclination angle of the surface crack and the orientation angle on I，II，III mode stress intensity factors were analyzed. I mode stress intensity factor increases along the crack front with increasing inclination angle. And I mode stress intensity factor of the same inclination angle is symmetrical with respect to the orientation angle of 90 degree. II，III mode stress intensity factors are the maximum when the inclination angle is equal to 45 degree. And the behavior of II，III mode stress intensity factors along crack front for the inclination angle of 15 and 30 degree is identical with that of inclination angle of 75 and 60 degree, respectively.

Comparison of Methods for Calculating Stress Intensity Factors for the Thread of a Pressure Vessel Closure and of a Gun Breech Ring

2003 ◽  
Vol 125 (3) ◽  
pp. 326-329 ◽  
Author(s):  
David P. Kendall
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Pressure Vessel ◽  
Continuous Distribution ◽  
Intensity Factors ◽  
Plane Normal ◽  
Proposed Modification ◽  
Distribution Of Stress

Non-mandatory Appendix D of Section VIII, Division 3 of the ASME Boiler and Pressure Vessel Code provides a method for calculating the stress intensity factors for the region of a thread root of a threaded closure. This method involves calculation of the distribution of stress acting on a plane normal to the axis of the thread. This distribution is fitted with several different cubic equations for different regions and the coefficients of these cubic equations are entered into an equation to calculate the distribution of stress intensity factor for each region. The values of stress intensity factor for each region after the first one are shifted to obtain a continuous distribution. In a paper to be presented at the August 2002 ASME Pressure Vessel and Piping Conference (Kendall 2002) the author compared the stress intensity factors calculated by the above Code method with those determined by Neubrand and Burns, 1999, using a weight function method. In Kendall, 2002, the stress intensity factors for this same closure design were calculated using the Code method and also calculated using a proposed modification of this method. The results showed slightly better agreement for the proposed modification of the Code method. This paper will report the details of these calculation methods and the results from Kendall, 2002. It will also give a comparison of the stress intensity factor results of these methods for a thread of a typical gun breech ring, and a comparison of the calculated fatigue crack growth lives.

Stress Intensity Factor Estimation for Embedded and Surface Cracks in an RPV Subjected to Yielding of Cladding

2006 ◽  
Author(s):  
Katsuyuki Shibata ◽  
Kunio Onizawa ◽  
Kazuhisa Tanaka ◽  
Masahide Suzuki
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Surface Crack ◽  
Pressure Vessel ◽  
Crack Tip ◽  
Estimation Scheme ◽  
Embedded Crack ◽  
Reactor Pressure ◽  
Factor Estimation

The cladding of an RPV (Reactor Pressure Vessel) at the inner surface may be subjected to a plastic yielding due to a high thermal stress under some severe overcooling events, while the stress in base metal remains elastic. The stress intensity factor estimation at the deepest crack tip of an embedded crack (EC) or a surface crack (SC) under such loadings is essential in the integrity assessment of an RPV. However, an elasto-plastic FE analysis is required to obtain the stress intensity factor on this problem generally. A solution for an under-clad crack (UCC) was developed by EDF based on numerous 2D FE computations. This paper proposes a simplified estimation scheme which takes the yielding of cladding into account. This scheme estimates the stress intensity factor at the deepest crack tip of an embedded crack or a surface crack. It is assumed that the stress singularity does not exist at the shallowest crack tip in the cladding. To estimate the stress intensity factor of an embedded crack, the crack shape is replaced by a semi-elliptical one to utilize existing solutions of SC. Case studies to examine the proposed estimation scheme were carried out for an UCC and SC subjected to the SBLOCA, SLB and PTS transients, which were defined by a international round robin PROSIR (Probabilistic Structural Integrity of a PWR Reactor Pressure Vessel) project being conducted by OECD/NEA/IAGE-WG. It was found that the proposed scheme gives a reasonable estimation of the stress intensity factor for an UCC and a SC.

Evaluation on an Internal Surface Crack in a Compound Tube

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
A. A. Ali ◽  
J. Purbolaksono ◽  
A. Khinani ◽  
A. Z. Rashid ◽  
F. Tarlochan
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Modulus Of Elasticity ◽  
Outer Part ◽  
Internal Surface ◽  
Intensity Factors ◽  
Inner Region

In this paper stress intensity factors of a longitudinal semielliptical surface crack on the inner surface in a compound tube subjected to internal pressure are presented. Variations of modulus of elasticity and thickness for the inner part of the tube are used in order to evaluate their effects on the normalized stress intensity factors. The boundary element method is used to analyze the problems. The increasing of thickness of the inner region causes decreasing values of the normalized stress intensity factor, as the modulus of elasticity for the inner part is greater than that of the outer part. Conversely, if the modulus of elasticity for the inner region is smaller, the increasing of thickness of the inner part would give increasing values of the normalized stress intensity factor. A larger inner radius and smaller thickness of the tube gives a higher normalized stress intensity factor.

The Effects of Residual Stress Distribution and Geometry of Component on the Stress Intensity Factor of Surface Crack

2005 ◽  
Author(s):  
Katsumasa Miyazaki ◽  
Masahito Mochizuki
Keyword(s):  
Residual Stress ◽  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Stress Distribution ◽  
Intensity Factor ◽  
Stress Field ◽  
Crack Growth ◽  
Surface Crack ◽  
Residual Stress Distribution ◽  
Intensity Factors

The stress intensity factor estimated by using the appropriate modeling of components is essential for evaluation of crack growth behavior in stress corrosion cracking. For the appropriate modeling of welded components with a crack, it is important to understand the effects of residual stress distribution and geometry of component on the stress intensity factor of surface crack. In this study, the stress intensity factors of surface crack under two assumed residual stress fields were calculated. As residual stress field, the bending type stress field (tension-compression) and the self-equilibrating stress field (tension-compression-tension) through the thickness were assumed. The geometries of components were plate and piping. The assumed surface cracks for evaluations were long crack in surface direction and semi-elliptical surface crack. Furthermore, the crack growth evaluations were conducted to understand the effects of residual stress distribution and geometry of component. Here, the crack growth evaluation means the simulation of increments of crack depth and length by using the crack growth property and stress intensity factors. From the comparison of stress intensity factors and crack growth evaluation for surface crack under residual stress field, the effects of residual stress distribution and geometry of component on the stress intensity factor of surface crack and appropriate modeling of cracked components were discussed.

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