Numerical study of the applicability of the η-factor method to J-resistance curve determination of steam generator tubes using non-standard specimens

• Non-standard fracture specimens obtained from steam generator tubes are proposed.
• The suitability of the η-factor method for estimating the J-integral is addressed.
• η-factor values are estimated using elastoplastic finite element analysis.
• High constraint conditions favor the validity of the η-factor method.
• η-factors based on CMOD are more valid than the η-factors derived from LLD.

The suitability of the η-factor method for the determination of J-resistance curves of thin walled steam generator tubes was evaluated using elastoplastic finite element analysis. Different candidate non-standard specimens’ geometries were considered. It was shown how high constraint conditions associated with deep cracks geometries and prevailing bending loads favor the η-factor validity while low constraint configurations resulted in a η-factors exhibiting a higher dependence on the applied load. It was also verified that η-factors based on the crack mouth opening displacement (CMOD) showed much less dependency on the loading level than η-factors derived from load line displacement (LLD).