Crack Opening Areas During High Temperature Operation

2002 ◽  
Author(s):  
S. F. Yellowlees ◽  
D. G. Hooton ◽  
J. K. Sharples ◽  
P. J. Budden ◽  
D. W. Dean
Keyword(s):  
Finite Element ◽  
Strain Field ◽  
Crack Opening ◽  
Rate Of Change ◽  
Secondary Creep ◽  
Stationary Crack ◽  
Transient Period ◽  
Dimensional Finite Element ◽  
Elastic Crack ◽  
High Temperature Operation

This paper presents results from two-dimensional finite element analyses of a centre cracked plate under both plane stress and plane strain conditions. The plate has been loaded in tension and secondary creep conditions have been assumed. The variation of the crack opening area with time has been calculated. It has been shown that the rate of change of the crack opening areas reduces with time up to the redistribution time which approximates the time to achieve steady creep conditions. Thereafter, the rate of change of crack opening area is constant. From curve fits to finite element results, a simplified expression for the rate of change of crack opening area of a stationary crack has been derived in terms of the elastic crack opening area, the creep strain rate, the elastic strain and two characteristic crack lengths (one for a strain field dominated by elastic strains and one for a strain field dominated by creep strains). This expression predicts the rate of change of the crack opening area both during the transient period up to the redistribution time and at all times thereafter.

Stress Intensity Factor and Elastic Crack Opening Displacement Solutions of Complex Cracks in Pipe Using Elastic Finite-Element Analyses

2015 ◽  
Vol 138 (1) ◽  
Author(s):  
Jae-Uk Jeong ◽  
Jae-Boong Choi ◽  
Nam-Su Huh ◽  
Yun-Jae Kim
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Internal Pressure ◽  
Closed Form ◽  
Crack Opening ◽  
Crack Depth ◽  
Loading Conditions ◽  
Axial Tension ◽  
Elastic Crack ◽  
Geometric Variables

In the present paper, the closed-form expressions for the stress intensity factors (SIFs) and the elastic crack opening displacements (CODs) of complex-cracked pipes are derived based on the systematic three-dimensional (3D) elastic finite-element (FE) analyses. The loading conditions that are evaluated include global bending moment, axial tension, and internal pressure. In terms of geometries, the geometric variables affecting the SIFs and the elastic CODs of complex-cracked pipes, i.e., the crack angle of through-wall cracks (TWCs), the crack depth of fully circumferential, internal surface cracks in the inner surface of pipe, and the ratio of pipe mean radius to thickness, are systematically considered in the present FE analyses. The FE analysis procedure employed in the present study has been validated against the existing solutions for the circumferential TWC pipes. Using the present FE results, the shape factors of SIF and elastic COD for complex-cracked pipes are tabulated as a function of geometric variables. The results are applied for closed-form expressions of SIF and elastic COD when the pipe is subjected to simple loading conditions of bending, axial tension, or internal pressure. The proposed closed-form expressions can estimate SIF and elastic COD of complex-cracked pipes within maximum differences of 2.4% and 5.9% with FE results, respectively.

Estimation of Elastic Crack Opening Displacement for Thin Elbows With Circumferential Through-Wall Cracks

2015 ◽  
Author(s):  
Min-Kyu Kim ◽  
Han-Bum Surh ◽  
Min-Gu Won ◽  
Nam-Su Huh ◽  
Moon-Ki Kim ◽  
...  
Keyword(s):  
Crack Opening Displacement ◽  
Nuclear Power ◽  
Crack Opening ◽  
Three Dimensional ◽  
Opening Displacement ◽  
Dimensional Finite Element ◽  
Elastic Crack ◽  
Thin Walled ◽  
Three Dimensional Finite Element ◽  
Leak Before Break

Leak-before-break (LBB) is an important concept that could confirm design and integrity evaluation of nuclear power plant piping. For the LBB analysis, the detective leakage rate should be calculated for a through-wall cracked pipes. For this calculation, the crack opening displacement (COD) calculation is essential. Recently, sodium faster reactor (SFR) which has thin-walled pipes with Rm/t ranged 30–40 was introduced and then the investigation of these thin walled pipes and elbows has received great attention in the LBB evaluation. In this context, the three-dimensional finite element (FE) analyses for thin elbows with circumferential crack under in-plane bending are carried out to investigate the elastic COD values. Finally, the solution for elastic COD which can cover sufficiently thin elbow is successfully addressed.

Estimates of Elastic Crack Opening Displacements of Slanted Through-Wall Cracks in Plate and Cylinder

2010 ◽  
Vol 132 (2) ◽  
Author(s):  
Nam-Su Huh ◽  
Do-Jun Shim ◽  
Yeon-Sik Yoo ◽  
Suhn Choi ◽  
Keun-Bae Park
Keyword(s):  
Finite Element ◽  
Crack Opening ◽  
Three Dimensional ◽  
Bending Moment ◽  
Element Model ◽  
Finite Element Analyses ◽  
Opening Displacement ◽  
Elastic Crack ◽  
Leak Before Break ◽  
The Finite Element Model

This paper provides tractable solutions for elastic crack opening displacement (COD) of slanted through-wall cracks in plates and cylinders. The solutions were developed via detailed three dimensional elastic finite element analyses. The COD values were calculated along the thickness at the center of the crack. As for the loading conditions, only remote tension was considered for the plates, whereas remote tension, global bending moment, and internal pressure were considered for the cylinders. The finite element model employed in the present analysis was verified by using existing solutions for a cylinder with an idealized circumferential through-wall crack. The present results can be used to evaluate leak rates of slanted through-wall cracks, which can be used as a part of a detailed leak-before-break analysis considering more realistic crack shape development.

Closure and Growth of Fatigue Cracks at Notches

1992 ◽  
Vol 114 (1) ◽  
pp. 1-7 ◽  
Author(s):  
R. C. McClung ◽  
H. Sehitoglu
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Fatigue Cracks ◽  
Crack Opening ◽  
Local Stress ◽  
Element Model ◽  
Rate Of Change ◽  
Growth Effect ◽  
Growth Data ◽  
Stress Ratios

The closure behavior of fatigue cracks growing out of notches is studied with an elastic-plastic finite element model. Crack opening stresses are shown to change significantly as the crack extends. Opening stresses are low at first and then gradually rise to stable values as the crack tip moves away from the notch field. These transient changes are not limited to the region of the original inelastic notch field. The rate of change of opening stresses with increasing crack length is a function of both nominal maximum stress and nominal stress ratio. Stable levels are reached more quickly at higher stress ratios and lower maximum stresses. These transient changes in Sopen have been emulated with a simple model which considers only changes in Sopen due to changes in the local stress field. The numerical results are quantitatively consistent with observed trends in experimental crack growth data, which show that accelerated crack growth can occur beyond the original notch plastic boundary. Finite element results and experimental data also both suggest that the accelerated short crack growth effect for cracks near notches is much less pronounced at higher stress ratios.

Three-Dimensional Finite Element Simulations of Elastic and Elastic-Plastic Crack Growth Using Automated Re-Meshing Techniques

2014 ◽  
Author(s):  
Tyler London ◽  
Simon D. Smith ◽  
Şefika Elvin Eren
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Three Dimensional ◽  
Offshore Structures ◽  
Element Analysis ◽  
Elastic Plastic ◽  
Dimensional Finite Element ◽  
Elastic Crack ◽  
Stability And Accuracy ◽  
Three Dimensional Finite Element

This paper concerns the numerical simulation of elastic and elastic-plastic crack growth in welded components. Three-dimensional, spline-based, automatic crack re-meshing algorithms have been developed at TWI to simulate crack propagation using the commercial finite element analysis software ABAQUS. These methods allow for fatigue crack growth simulations employing the Paris law, mean stress effects and more advanced elastic crack growth laws, and incorporate nodal release techniques or iterative stationary crack methods coupled with experimentally measured tearing resistance curves for elastic-plastic crack growth. The flexibility, stability and accuracy of these numerical methods are demonstrated through several examples. The application of the crack growth simulations to full-life engineering critical assessments (ECA) of offshore structures is also described and demonstrated.

Measurement of Work of Adhesion on Wafers for Direct Bonding

2003 ◽  
Vol 782 ◽  
Author(s):  
Kevin T. Turner ◽  
S. Mark Spearing
Keyword(s):  
Finite Element ◽  
Crack Front ◽  
Crack Opening ◽  
Three Dimensional ◽  
Strain Energy Release ◽  
Element Model ◽  
Work Of Adhesion ◽  
Dimensional Finite Element ◽  
Three Dimensional Finite Element ◽  
Opening Method

ABSTRACTThe displacement loaded double cantilever beam (DCB), often referred to as the blade-insertion test or crack-opening method by the wafer bonding community, has become a common method for evaluating the work of adhesion of bonded wafer pairs. The test, while easy to perform, often yields results with large scatter and questionable accuracy. The mechanics of the specimen are investigated in detail in the current work. Expressions that demonstrate how wafer bow may lead to residual stresses that result in large errors in the calculated work of adhesion are developed. A three-dimensional finite element model is used to show that due to the circular wafer geometry and silicon anisotropy there is a large variation of the strain energy release rate across a straight crack front. The model is used to predict the actual crack front shape and shows good agreement with experiments. The results of the finite element simulations are compared to the traditional expression used for data reduction and implications of the model highlighted.

Numerical Investigation to Examine the Effect of Introducing a Crack in a Residual Stress Field

2008 ◽  
Author(s):  
Simon Kamel ◽  
Noel P. O’Dowd ◽  
Kamran M. Nikbin
Keyword(s):  
Residual Stress ◽  
Finite Element ◽  
Stress Field ◽  
Crack Opening ◽  
Crack Tip ◽  
Residual Stress Field ◽  
Element Mesh ◽  
Crack Tip Fields ◽  
Dimensional Finite Element ◽  
Definition Of

This paper presents a detailed two dimensional finite-element study to examine the effect of introducing a crack either progressively or instantaneously into a residual stress field. A progressive crack is defined as a crack which is introduced in fixed increments of crack extension until the desired crack length is achieved. An instantaneous crack is one in which a crack of the required length is introduced instantaneously into the finite-element mesh. Inspection is made of the crack tip fields and the crack opening displacements. A modified definition of the J-integral, which accounts for the initial plastic strain due to residual stress, is assessed, in order to examine its ability to characterise the intensity of the near crack tip fields. The implications of the results on fracture assessment of structural components are discussed.

Finite Element Analysis of Nonuniformity of Tires with Imperfections5

2007 ◽  
Vol 35 (3) ◽  
pp. 226-238 ◽  
Author(s):  
K. M. Jeong ◽  
K. W. Kim ◽  
H. G. Beom ◽  
J. U. Park
Keyword(s):  
Finite Element Analysis ◽  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Radial Force ◽  
Element Analysis ◽  
The Finite Element Analysis ◽  
Dimensional Finite Element ◽  
Force Variation ◽  
Three Dimensional Finite Element

Abstract The effects of variations in stiffness and geometry on the nonuniformity of tires are investigated by using the finite element analysis. In order to evaluate tire uniformity, a three-dimensional finite element model of the tire with imperfections is developed. This paper considers how imperfections, such as variations in stiffness or geometry and run-out, contribute to detrimental effects on tire nonuniformity. It is found that the radial force variation of a tire with imperfections depends strongly on the geometrical variations of the tire.

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