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.

The Singularity of Stress near the Tip of a Crack Perpendicular to an Elastically Mismatched Bimaterial Interface

2014 ◽  
Vol 574 ◽  
pp. 48-52
Author(s):  
Ming Song ◽  
Hao Yong Li ◽  
You Tang Li ◽  
Min Zheng
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Finite Element Methods ◽  
Stress Intensity Factors ◽  
Bimaterial Interface ◽  
Intensity Factors ◽  
Material Combination ◽  
Single Material

This Based on the elastic theory of a crack perpendicular to and terminating at bimaterial interface, a generalized expression of the stress intensity factor is provided for a crack in single material and a crack perpendicular to bimaterial interface, finite element methods are used to calculate the stress intensity factors. The influences of the material combination and crack length on the the stress intensity factors were investigated. Results show that when the crack terminates at bimaterial interface, singular order ofKIis different from that of single material, and the values ofKIincrease with increasingE1/E2andμ1/μ2.

Stress Intensity Factors for Unequal Longitudinal-Radial Cracks in Thick-Walled Cylinders

1991 ◽  
Vol 113 (1) ◽  
pp. 22-27 ◽  
Author(s):  
J. L. Desjardins ◽  
D. J. Burns ◽  
R. Bell ◽  
J. C. Thompson
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Finite Elements ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Two Dimensional ◽  
Intensity Factors ◽  
Radial Cracks ◽  
Good Agreement

Finite elements and two-dimensional photoelasticity have been used to analyze thick-walled cylinders which contain arrays of straight-fronted, longitudinal-radial cracks of unequal depth. The stress intensity factor K1 has been computed for the dominant crack and for some of the surrounding cracks. Cylinders with 2, 4, 6, 8, 16, 36 and 40 cracks have been considered. Good agreement has been obtained between the experimental and the numerical results and, for cylinders with 2 or 4 cracks, with previously published predictions. The results for all of the foregoing cases are used to develop simple, approximate techniques for estimating K1 for the dominant crack, when the total number of cracks is different from those that have been considered herein. Estimates of K1 obtained by these techniques agree well with corresponding finite element results.

Study on Stress Intensity Factors for Circumferential Cracked Elliptical Pipes under Tension

2011 ◽  
Vol 299-300 ◽  
pp. 912-916
Author(s):  
W. Wang ◽  
Y. M. Cai ◽  
Y.J. Xie
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Virtual Work ◽  
Principle Of Virtual Work ◽  
Intensity Factors

Stress intensity factor is one of the most important parameters in fracture mechanics. Based on the principle of virtual work and bending theory, this paper proposes a method to estimate the stress intensity factor for circumferential cracked elliptical pipes and derive the expression of the stress intensity factor for circumferential cracked elliptical pipes under tension. The compare of the result of this method and finite element method shows this method is credible and convenient.

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.

Numerical Determination of Stress Intensity Factors Using ABAQUS

2014 ◽  
Author(s):  
Xian-Kui Zhu
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Three Dimensional ◽  
Pressure Vessels ◽  
Intensity Factors ◽  
Element Analysis ◽  
Linear Elastic ◽  
Displacement Extrapolation Method

Crack assessments for pressure vessels often need to quantify the crack driving force — stress intensity factor K with the linear-elastic fracture mechanics methods. Different numerical methods have been developed to calculate the stress intensity factors for complex cracks. Of which, four typical methods, i.e., the displacement extrapolation method, the virtual crack closure technique (VCCT), the J-integral conversion method, and the direct K output method are selected and evaluated in this paper using the finite element analysis (FEA) and ABAQUS software. The evaluations are performed based on the benchmark FEA calculations in the linear-elastic conditions for the central-cracked panel (CCP) specimen in the two-dimensional (2D) plane strain conditions. The “best method” is then determined and used to calculate the stress intensity factor for the CCP specimen with a through-thickness crack in the three-dimensional (3D) conditions. The results show that ABAQUS can simply determine very accurate K values for both 2D and 3D cracks.

Stress-Intensity Factors for Internal and External Surface Cracks in Cylindrical Vessels

1982 ◽  
Vol 104 (4) ◽  
pp. 293-298 ◽  
Author(s):  
I. S. Raju ◽  
J. C. Newman
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Internal Pressure ◽  
Stress Intensity Factors ◽  
Crack Depth ◽  
Surface Cracks ◽  
Stress Distributions ◽  
Intensity Factors

The purpose of this paper is to present stress-intensity factor influence coefficients for a wide range of semi-elliptical surface cracks on the inside or outside of a cylinder. The crack surfaces were subjected to four stress distributions: uniform, linear, quadratic, and cubic. These four solutions can be superimposed to obtain stress-intensity factor solutions for other stress distributions, such as those caused by internal pressure and by thermal shock. The results for internal pressure are given herein. The ratio of crack depth to crack length from 0.2 to 1; the ratio of crack depth to wall thickness ranged from 0.2 to 0.8; and the ratio of wall thickness to vessel radius was 0.1 or 0.25. The stress-intensity factors were calculated by a three-dimensional finite-element method. The finite-element models employ singularity elements along the crack front and linear-strain elements elsewhere. The models had about 6500 degrees of freedom. The stress-intensity factors were evaluated from a nodal-force method. The present results were also compared to other analyses of surface cracks in cylinders. The results from a boundary-integral equation method agreed well (±2 percent), and those from other finite-element methods agreed fairly well (±10 percent) with the present results.

Computations of Stress Intensity Factors for Deep Cracks in Plates by Using the Tetrahedral Finite Element

2012 ◽  
Author(s):  
Hiroshi Okada ◽  
Hirohito Koya ◽  
Hiroshi Kawai ◽  
Yinsheng Li
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Stress Intensity Factors ◽  
Structural Integrity ◽  
Intensity Factors ◽  
Welded Structures ◽  
Elliptical Cracks

In this paper, stress intensity factor solutions for deep half-elliptical cracks that are applicable to the structural integrity evaluations of welded structures are presented. Welded structures generally have some weld residual stresses resulting in stress corrosion crackings (SCCs). This paper describes a simple way to compute the stress intensity factors under the weld-residual stresses and the mode I stress intensity factor solutions for deep half-elliptical cracks. The residual stresses are set to vary proportional to the constant, the linear, the quadratic and the cubic functions of x which is the distance from the plate surface. Although we use a straightforward finite element method to perform the computations, we can quickly generate the stress intensity factor solutions as we make use of automatic mesh generation program for the tetrahedral finite element. Thus, it is very tractable to generate the finite element models with cracks. Furthermore, present solutions can be compared with those of Li et al. which are also presented in PVP 2012. We conclude that present method is useful for the evaluations of SIFs of cracks under the residual stresses.

Analysis of Surface Flaw in Pressure Vessels by a New 3-Dimensional Alternating Method

1982 ◽  
Vol 104 (4) ◽  
pp. 299-307 ◽  
Author(s):  
T. Nishioka ◽  
S. N. Atluri
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Surface Crack ◽  
Crack Surface ◽  
Pressure Vessels ◽  
Pressure Loading ◽  
Intensity Factors ◽  
Alternating Method ◽  
Magnification Factors

An alternating method, in conjunction with the finite element method and a newly developed analytical solution for an elliptical crack in an infinite solid, is used to determine stress intensity factors for semi-elliptical surface flaws in cylindrical pressure vessels. The present finite element alternating method leads to a very inexpensive procedure for routine evaluation of accurate stress intensity factors for flawed pressure vessels. The problems considered in the present paper are: (i) an outer semi-elliptical surface crack in a thick cylinder, and (ii) inner semi-elliptical surface cracks in a thin cylinder which were recommended for analysis by the ASME Boiler and Pressure Vessel Code (Section III, App. G, 1977). For each crack geometry of an inner surface crack, seven independent loadings, such as internal pressure loading on the cylinder surface and polynomial pressure loadings from constant to fifth order on the crack surface, are considered. From the analyses of these loadings, the magnification factors for the internal pressure loading and the polynomial influence functions for the polynomial crack surface loadings are determined. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived by using the polynomial influence functions to check the internal consistency of the present analysis. These values agree excellently with the magnification factors obtained directly. The present results are also compared with the results available in literature.

Stress Intensity Factors for Circular-Arc Cracks in Plates

2018 ◽  
Author(s):  
D. J. Shim ◽  
S. Tang ◽  
T. J. Kim ◽  
N. S. Huh
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Stress Intensity Factors ◽  
Crack Model ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Element Analysis ◽  
Crack Face ◽  
Circular Arc

Stress intensity factor solutions are readily available for flaws found in pipe to pipe welds or shell to shell welds (i.e., circumferential/axial crack in cylinder). In some situations, flaws can be detected in locations where an appropriate crack model is not readily available. For instance, there are no practical stress intensity factor solutions for circular-arc cracks which can form in circular welds (e.g., nozzle to vessel shell welds and storage cask closure welds). In this paper, stress intensity factors for circular-arc cracks in finite plates were calculated using finite element analysis. As a first step, stress intensity factors for circular-arc through-wall crack under uniform tension and crack face pressure were calculated. These results were compared with the analytical solutions which showed reasonable agreement. Then, stress intensity factors were calculated for circular-arc semi-elliptical surface cracks under the lateral and crack face pressure loading conditions. Lastly, to investigate the applicability of straight crack solutions for circular-arc cracks, stress intensity factors for circular-arc and straight cracks (both through-wall and surface cracks) were compared.

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