Elasto-plastic fracture mechanics is commonly used for defect assessments in Nuclear Industry. Most of the approaches are based on the crack driving force J which is compared to a fracture resistance parameter. This fracture resistance parameter cannot be measured directly, but requires either J engineering formulae or Finite Element computations. The η(Eta) factor approach  is the most popular method allowing deriving fracture resistance from test records. One of the issue is the dependency of this factor to strain-hardening, namely for the shallow cracks.
This paper analyzes the effect of strain hardening on Eta factor solutions for two types of loading. Detailed Finite Element results are provided for Single Edge Cracked specimens under bending or tension. The results are compared to other formulae from the literature and new formulae are proposed.