Verification of the Combination Rules of Multiple Flaws in ASME B&PV Code Section XI: A Case Study of Two Adjacent Surface Planar Flaws

2011 ◽  
Vol 133 (2) ◽  
Author(s):  
Toshihisa Nishioka ◽  
Guangqin Zhou ◽  
Takehiro Fujimoto
Keyword(s):  
Finite Element ◽  
Cost Effective ◽  
Pressure Vessels ◽  
Surface Cracks ◽  
Combination Rule ◽  
Combination Rules ◽  
Alternating Method ◽  
Vna Solution ◽  
Coplanar Cracks

In nuclear pressure vessels, multiple surface cracks are often found by regular inspection. In order to evaluate the integrity of the vessels, ASME B&PV Code Section XI provides the flaw combination rules; however, its accuracy has not been clarified yet. For the analyses of interacting multiple semi-elliptical surface cracks, in 1983 Nishioka and Atluri developed the Vijayakumar, Nishioka, and Atluri (VNA) solution-finite element alternating method which is highly accurate and cost effective. Using this highly accurate VNA-finite element alternating method, the case of extremely closely located two interacting coplanar cracks was analyzed. From the numerical results, it is found that the B&PV Code Section XI provides a conservative flaw combination rule. Therefore, the B&PV Code Section XI is precisely verified by modern and accurate computational technologies.

Analysis of Interaction Behavior of Surface Flaws in Pressure Vessels

1986 ◽  
Vol 108 (1) ◽  
pp. 24-32 ◽  
Author(s):  
P. E. O’Donoghue ◽  
T. Nishioka ◽  
S. N. Atluri
Keyword(s):  
Finite Element ◽  
Stress Intensity ◽  
Pressure Vessels ◽  
Influence Functions ◽  
Surface Cracks ◽  
Intensity Factors ◽  
Alternating Method ◽  
Circumferential Crack ◽  
Magnification Factors ◽  
Surface Flaws

The evaluation of stress intensity factors for surface flaw problems and, in particular, semi-elliptical surface cracks in cylindrical pressure vessels has been well developed using the finite element alternating method. Some of the examples presented here include the interaction effects due to multiple internal longitudinal surface cracks in cylinders as recommended for analysis in the ASME Boiler and Pressure Vessel Code (Section XI). For each crack geometry, several loading cases are considered including internal pressure and polynomial pressure loadings from constant to fourth order. By the method of superposition, the magnification factors for internally pressurized cylinders are rederived using the polynomial influence functions. These influence functions give useful information for design purposes such as in the analysis of a thermally shocked cylinder. The problem of a single circumferential crack in a cylinder is also investigated using the finite element alternating method, and a number of results for such problems are also presented here.

Finite Element Alternating Method for Interacting Surface Cracks

2007 ◽  
Vol 120 ◽  
pp. 147-153 ◽  
Author(s):  
Masayuki Kamaya ◽  
Toshihisa Nishioka
Keyword(s):  
Finite Element ◽  
Crack Size ◽  
Surface Cracks ◽  
Combination Rules ◽  
Element Analysis ◽  
Crack Face ◽  
Direct Evaluation ◽  
Alternating Method ◽  
The Finite Element Analysis ◽  
The Difference

The finite element alternating method (FEAM), in conjunction with the finite element analysis (FEA) and the analytical solution for an elliptical crack in an infinite solid subject to arbitrary crack-face traction, can derive the stress intensity factor (SIF) of surface cracks by using the FEA results for an uncracked body. In the present study, the FEAM was applied to evaluations of SIF for noncoplanar multiple surface cracks. The SIF was evaluated for two surface cracks of dissimilar size, and three crack of the same size. The results suggested that the interaction is greatly affected by the relative crack size and negligible when the difference in the crack size is large enough, and the interaction can be evaluated by taking into account the adjacent cracks even if there are many cracks around them. Finally, the crack growth simulations were conducted and a possibility of the direct evaluation of influence of interaction between adjacent crack without using the combination rules was revealed.

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.

Analysis of Surface Crack in Cylinder by Finite Element Alternating Method

2005 ◽  
Vol 127 (2) ◽  
pp. 165-172 ◽  
Author(s):  
Masayuki Kamaya ◽  
Toshihisa Nishioka
Keyword(s):  
Finite Element ◽  
Crack Growth ◽  
Surface Cracks ◽  
Inclined Crack ◽  
Element Analysis ◽  
Crack Face ◽  
Simple Method ◽  
Alternating Method ◽  
The Finite Element Analysis ◽  
Inclined Surface

The finite element alternating method (FEAM), in conjunction with the finite element analysis (FEA) and the analytical solution for an elliptical crack in an infinite solid subject to arbitrary crack-face traction, is used for evaluating the stress intensity factor (SIF) of surface cracks in a cylinder. The major advantage of this method is that the SIF can be calculated by using the FEA results for an uncracked body. A newly developed system allows the FEAM to be performed by a simple method, which consists of the conventional FEA for an uncracked body and a subroutine for the FEAM alternating procedure. It is shown that the system can derive the precise SIF of circumferential, longitudinal, and inclined surface cracks in a cylinder. The crack growth predictions are performed for an inclined crack and projected longitudinal and circumferential crack in a cylinder. The results suggests that the crack characterizing procedure prescribed in Sec. XI may cause an unconservative evaluation in the crack growth prediction, and that the FEAM is valid for complex problems, to which the SIF evaluation by the FEA cannot be adopted easily.

Constraint of Semi-Elliptical Surface Cracks in T and L-Joints

2006 ◽  
Vol 326-328 ◽  
pp. 939-944
Author(s):  
Hyung Yil Lee ◽  
Yun Jae Kim
Keyword(s):  
Finite Element ◽  
Structural Characteristics ◽  
Pressure Vessels ◽  
Surface Cracks ◽  
Spring Model ◽  
Constraint Effect ◽  
T Stress ◽  
Line Spring Model ◽  
Parameter Approach ◽  
Two Parameter

Critical defects in pressure vessels and pipes are generally found in the form of a semielliptical surface crack, and the analysis of which is consequently an important issue in engineering fracture mechanics. Furthermore, in addition to the traditional single parameter K or J-integral, the second parameter like T-stress should be measured to quantify the constraint effect. In this work, the validity of the line-spring model is investigated by comparing line-spring J-T solutions to the reference 3D finite element J-T solutions. A full 3D-mesh generating program for semi-elliptical surface cracks is employed to provide such reference 3D solutions. Then some structural characteristics of the surface-cracked T and L-joints are studied by mixed mode line-spring finite element. Negative T-stresses observed in T and L-joints indicate the necessity of J-T two parameter approach for analyses of surface-cracked T and L-joints.

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