SIF Calculation for Two Cracks Emanating From the Internal Boundary of a Tube

1990 ◽  
Vol 112 (4) ◽  
pp. 374-377
Author(s):  
Y. H. Wang ◽  
C. Z. Li
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Internal Pressure ◽  
Crack Length ◽  
Collocation Method ◽  
Outer Boundary ◽  
Internal Boundary ◽  
Collinear Cracks ◽  
Boundary Collocation Method

The stress intensity factor (SIF) corresponding to two collinear cracks emanating from the internal boundary of a tube is calculated by boundary collocation method (BCM). Uniform internal pressure acts in the cylinder and on the crack surfaces or a uniform external tension on the outer boundary. For different ratios of the internal to the external radius, Ri/Re, and different ratios of the crack length to the cylinder thickness, 1/(Re−Ri), SIF values have been obtained. At the same time, the calculation shows that the convergence of the method is satisfactory.

Stress Intensity Factor and Elastic COD for Circumferential Through-Wall Cracks in the Interface Between an Elbow and a Straight Pipe Under Internal Pressure

2015 ◽  
Author(s):  
Youn-Young Jang ◽  
Nam-Su Huh ◽  
Jae-Uk Jeong ◽  
Ki-Seok Kim ◽  
Woo-Yeon Cho
Keyword(s):  
Stress Intensity Factor ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Internal Pressure ◽  
Crack Length ◽  
Crack Opening ◽  
Radius Of Curvature ◽  
Piping System ◽  
Straight Pipe ◽  
Geometric Variables

Leak-Before-Break (LBB) is one of important approaches applied to nuclear piping design. In the LBB assessment, it is important to evaluate crack instability and to predict leak rate based on a fracture mechanics concept, in which an idealized straight pipes with through-wall cracks (TWCs) are generally considered in the typical LBB analysis. On the other hand, in nuclear piping system, elbows are often connected with straight pipes by welding, in which cracks could occur as well known. Hence, accurate assessment needs to be performed for cracks in weldments joining an elbow and attached straight pipe. In the previous study, it has been revealed that crack instability of a TWC in the interface between an elbow and a straight pipe under bending moment could be different with that of a straight pipe with a TWC depending on a change of pipe thickness, radius of curvature and crack length. Especially, elbows attached to a pipe were more severe than straight pipes for relatively shorter crack length. Thus, a need of engineering solutions for cracks in the interface between an elbow and a pipe is raised for accurate LBB analysis on nuclear piping system. In this present study, stress intensity factor (SIF) and crack opening displacement (COD) are estimated via detailed 3-dimensional finite element (FE) elastic analyses for circumferential TWCs in the interface between an elbow and a straight pipe subjected to internal pressure. The geometric variables (pipe thickness, radius of curvature and crack length) affecting SIFs and CODs were systematically considered in order to cover actual ranges of geometric variables. Also, the effect of elbow on elastic fracture parameters was investigated by comparing the present results with the results from the previous straight pipe solution. Moreover, based on the present FE results, the shape factors (F, V) used for calculating SIFs and CODs are proposed for circumferential TWCs in the interface between an elbow and a pipe. The present results can be used to perform the accurate LBB assessment for nuclear piping system including elbows welded to a straight pipe.

scholarly journals Soil Load on Plastic Pipe and its Influence on Lifetime

2019 ◽  
Vol 69 (3) ◽  
pp. 101-106
Author(s):  
Jan Poduška ◽  
Pavel Hutař ◽  
Andreas Frank ◽  
Jaroslav Kučera ◽  
Jiří Sadílek ◽  
...  
Keyword(s):  
Finite Element Method ◽  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Residual Stresses ◽  
Internal Pressure ◽  
Crack Length ◽  
Power Law ◽  
Lifetime Estimation

AbstractLifetime of plastic pipes can be estimated by integration of a power law describing the crack kinetics. However, this procedure requires an FEM (finite element method) calculation of the possible crack propagation in the pipe to obtain stress intensity factor dependency on the crack length. It is very important for the simulation to consider every possible load that is acting on the pipe. This contribution deals with FEM modelling of a pipe that is loaded by internal pressure, residual stresses and soil loads. Comparison of the factors and pipe lifetime estimation is carried out.

Effect of specimen crack lengths on stress intensity factor for Al6061-TiC composites using experimental and 3D numerical methods

2017 ◽  
Vol 8 (5) ◽  
pp. 506-515 ◽  
Author(s):  
Raviraj M.S. ◽  
Sharanaprabhu C.M. ◽  
Mohankumar G.C.
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
Crack Length ◽  
Finite Element Simulations ◽  
Experimental Results ◽  
Crack Mouth Opening Displacement ◽  
3D Finite Element ◽  
Content Type

Purpose The purpose of this paper is to present the determination of critical stress intensity factor (KC) both by experimental method and three-dimensional (3D) finite element simulations. Design/methodology/approach CT specimens of different compositions of Al6061-TiC composites (3wt%, 5wt% and 7wt% TiC) with variable crack length to width (a/W=0.3-0.6) ratios are machined from as-cast composite block. After fatigue pre-cracking the specimens to a required crack length, experimental load vs crack mouth opening displacement data are plotted to calculate the KC value. Elastic 3D finite element simulations have been conducted for CT specimens of various compositions and a/W ratios to compute KC. The experimental results indicate that the magnitude of KC depends on a/W ratios, and significantly decreases with increase in a/W ratios of the specimen. Findings From 3D finite element simulation, the KC results at the centre of CT specimens for various Al6061-TiC composites and a/W ratios show satisfactory agreement with experimental results compared to the surface. Originality/value The research work contained in this manuscript was conducted during 2015-2016. It is original work except where due reference is made. The authors confirm that the research in their work is original, and that all the data given in the article are real and authentic. If necessary, the paper can be recalled, and errors corrected.

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