Influences of some materials on J-estimation methods for pipes with circumferential surface cracks

The approximate calculation methods (SC.ENG1 and SC.ENG2) for the J-integra l for pipes with circumferential surface cracks are discussed and three-dim ensional elastic-plastic finite element models for circumferentially surfac e-cracked pipe are conducted to evaluate the accuracy of these methods for different pipe materials used in China. The numerical studies verify that t he SC.ENG2 method provides more accurate estimates of J than SC.ENG1 Based on three-dimensional elastic-plastic fracture analysis, the distribution of the local J-integral along the front of a circumferential constant-depth i nternal surface crack is investigated and the influences of different pipe materials with different yield plateaux on J-integral values are discussed. The validity of SC.ENG1 and SC.ENG2 J-integral estimation methods for pipe steel materials with different yield plateaux used in China are examined i n detail and the SC.ENG2 method is found to provide reasonable estimates of J for materials with yield plateaux. (C) 2001 Elsevier Science Ltd. All ri ghts reserved.