A SIMPLIFIED EVALUATION OF STRESS INTENSITY FACTORS FOR A SMALL DIAMETER PIPE PENETRATING A THICK PLATE

a/c –aspect ratio Recent trouble with stress corrosion cracking in the internal parts of boiling water reactors and similar issues found in pressurized water reactors has prompted interest in developing simplified methods to determine stress intensity factors for such cracks. Currently, there are many practical and accurate simplified methods to calculate stress intensity factors for a surface crack in plates and pipes. However, there are none that deal with the complex geometry that can arise within the reactors. The complex geometry found within the vessels often entails reentrant corners, welds, holes, and other stress amplifiers. This paper sets forth a means by which some commonly known and accepted simplified solutions to cracks in pipes and plates can be slightly modified to improve the accuracy of stress intensity factors when applied to this complex geometry. The effort to do so included numerical modeling in two and three dimensions of both the cracked and uncracked body with a variety of assumed surface flaws. From this, it was confirmed that the simplified methods lead to exceedingly conservative estimates for the stress intensity factors of the complex geometry. Finally, a ratio of the axisymmetric fracture analyses was applied to the simplified three dimensional results which serves as a correction factor to improve the accuracy of the simplified method. a/t – normalized crack depth t – material thicknes