Experimental determination of J-resistance curves of nuclear steam generator tubes

The experimental determination of room temperature J-resistance curves of thin walled Incoloy 800 nuclear steam generator tubes was studied. Different non-standard specimens' geometries were considered, including circumferential and longitudinal trough-wall cracks. J-integral values were estimated using the η-factor method from the experimental load vs. LLD and CMOD displacement records. Circumferential cracks led to higher J-resistance curves than longitudinal cracks indicating a degree of anisotropy in the fracture properties. Low constraint conditions promoted by predominant tensile loadings gave higher J-resistance curves than bending configurations. Details associated with the fatigue pre-cracking procedure and crack length monitoring along the tests are presented.