VERIFICATION OF FAT VALUES FOR THE APPLICATION OF THE NOTCH STRESS CONCEPT WITH THE REFERENCE RADII rref=1.00 AND 0.05 mm

For the verification of the FAT225 value suggested in the IIW Recommendations for the notch stress concept with the reference radius r(ref) = 1.00 mm and of FAT630 for r(ref) = 0.05 mm, investigations were carried out with fully and non-fully penetrated welds, and with non-fully penetrated welds with circular and long holes. The FAT values were confirmed by fatigue tests carried out under the stress ratio R = 0.5. However, in the case of low stress concentrations, e.g. weld toes of butt welds, when r(ref) = 0.05 mm is applied, the FAT class should be downgraded from 630 to 400 MPa to account for the size effect of larger maximum stressed material volumes.