Calculation of the Stress Intensity Factors for Elliptical Cracks Embedded in a Weld under Tensile Loading I：Single Crack

2011 ◽  
Vol 217-218 ◽  
pp. 1419-1424 ◽  
Author(s):  
Xiao Yu Liu ◽  
Cai Fu Qian ◽  
Hui Fang Li ◽  
Hui Zheng
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Maximum Stress ◽  
Numerical Solutions ◽  
Pressure Vessels ◽  
Intensity Factors ◽  
Maximum Stress Intensity ◽  
Embedded Crack ◽  
Elliptical Cracks ◽  
Maximum Stress Intensity Factor

In this paper, an embedded elliptical crack in a weld of pressure vessels under tension was taken into consideration, and stress intensity factors at the crack tip were calculated numerically with the emphasis on the influences of the weld surface. It is found that when the embedded depth is 4 times larger than the minor semi-axis of the ellipse, the weld surface effects on the crack can be neglected and the numerical solutions for the stress intensity factors well agree with the analytical ones. This result can be used to distinguish a shallow embedded crack from a deep embedded crack. It is also found that the point with maximum stress intensity factor is always located at the end of minor axis of the ellipse no mater the shape of the ellipse is and how deep it was embedded.

Calculation of the Stress Intensity Factors for Elliptical Cracks Embedded in a Weld under Tensile Loading II：Double Cracks

2011 ◽  
Vol 217-218 ◽  
pp. 1425-1429
Author(s):  
Xiao Yu Liu ◽  
Cai Fu Qian ◽  
Hui Fang Li ◽  
Hui Zheng
Keyword(s):  
Stress Intensity ◽  
Stress Intensity Factors ◽  
Major Axis ◽  
Pressure Vessels ◽  
Intensity Factors ◽  
Major Semi Axis ◽  
Crack Interactions ◽  
Maximum Stress Intensity ◽  
Embedded Crack ◽  
Elliptical Cracks

In this paper, double embedded elliptical cracks in a weld of pressure vessels under tension was taken into consideration, and stress intensity factors at the crack tip were calculated with the emphasis on the interaction between cracks. It is found that when the distance between the double embedded elliptical cracks is larger than the major semi-axis of the ellipse, influence between the cracks can be neglected. Unlike the single embedded crack, owing to the crack interactions, the point with maximum stress intensity factor is not always at the end of the minor axis of the ellipse, it may swift to the end of major axis, especially when the ellipse is close to a circle.

Observation of Crack Growth Behavior of 400μm Cracks in 4.762mm Silicon Nitride Balls under Cyclic Compressive Load

2019 ◽  
Vol 814 ◽  
pp. 335-339
Author(s):  
Takumi Toriki ◽  
Tomoya Matsui ◽  
Katsuyuki Kida
Keyword(s):  
Stress Intensity ◽  
Silicon Nitride ◽  
Stress Intensity Factors ◽  
Maximum Stress ◽  
Compressive Load ◽  
Growth Behavior ◽  
Crack Growth Behavior ◽  
Intensity Factors ◽  
Cyclic Pressure ◽  
Maximum Stress Intensity

In order to investigate the effect of pre-crack lengths on silicon nitride balls under cyclic pressure loads, the pre-crack lengths ranging from 400μm to 500μm were observed. Their growth behavior was compared to that of 200μm to 300μm pre-cracks. Furthermore, the initial threshold limits of their maximum stress intensity factors were measured.

Determination of Stress Intensity Factors for Gradient Stress Fields

1977 ◽  
Vol 99 (3) ◽  
pp. 477-484 ◽  
Author(s):  
J. M. Bloom ◽  
W. A. Van Der Sluys
Keyword(s):  
Stress Intensity ◽  
Crack Length ◽  
Stress Intensity Factors ◽  
Maximum Stress ◽  
Nuclear Industry ◽  
Stress Fields ◽  
Polynomial Method ◽  
Intensity Factors ◽  
Asme Code ◽  
Linear Envelope

This paper evaluates eight different analytical procedures used in determining elastic stress intensity factors for gradient or nonlinear stress fields. From a fracture viewpoint, the main interest in this problem comes from the nuclear industry where the safety of the nuclear system is of concern. A fracture mechanics analysis is then required to demonstrate the vessel integrity under these postulated accident conditions. The geometry chosen for his study is that of a 10-in. thick flawed plate with nonuniform stress distribution through the thickness. Two loading conditions are evaluated, both nonlinear and both defined by polynomials. The assumed cracks are infinitely long surface defects. Eight methods are used to find the stress intensity factor: 1–maximum stress, 2–linear envelope, 3–linearization over the crack length from ASME Code, Section XI, 4–equivalent linear moment from ASME Code, Section III, Appendix G for thermal loadings, 5–integration method from WRC 175, Appendix 4 for thermal loadings, 6–8-node singularity (quarter-point) isoparametric element in conjunction with the displacement method, 7–polynomial method, and 8–semi-infinite edge crack linear distribution over crack. Comparisons are made between all eight procedures with the finding that the methods can be ranked in order of decreasing conservatism and ease of application as follows: 1–maximum stress, 2–linear envelope, 3–linearization over the crack length, 4–polynomial method, and 5–singularity element method. Good agreement is found between the last three of these methods. The remaining three methods produce nonconservative results.

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.

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