An Engineering Fracture Mechanics Analysis of the Pilgrim I Nozzle-to-Pressure Vessel Weld Discontinuities.

摘要

The influence function (IF) method of calculation of stress intensity factor (K sub I)(a) is applied to the case of a semicircular surface crack,of radius a,used to model a discontinuity revealed by in-service inspection of a nozzle-to-shell weld in Pilgrim I pressure vessel. The (K sub I) calculations obtained in Section 2for two complex thermal stress distributions and a combined stress distribution encountered in the nozzle weld,are compared with previous calculations based upon the 'Evaluation of Flaw Indications'method described in the ASME Boiler and Pressure Vessel Code. It is shown that a substantial difference exists between the (K sub I)(a) values calculated by the Code method and the IF method,except, coincidentally,in the vicinity of the specific flaw size (a = 0.9in.) revealed by inspection of the Pilgrim vessel. For crack sizes substantially greater than 1.0in., (K sub I)(a) values calculated by the Code method are significantly larger than those calculated by the IF method. The IF method has the potential to improve and affect the conclusions of future analyses of structures with imperfections.