Creep-fatigue evaluation of stainless steel welded joints in FBR class 1 components

This paper describes a creep-fatigue evaluation method of 316FR welded joints proposed for the design of large-scale Japanese fast breeder reactors. The mechanism that cause the life reduction of welded joints were assumed to be stress/strain concentration due to the discontinuity of inelastic deformation properties within welded joints and the weaker strength of weld metal. This was verified by FE-analyses that simulated uniaxial fatigue/creep-fatigue tests of 316FR welded joints. A creep-fatigue evaluation method for 316FR welded joints was consequently proposed. The method was based on the elastic follow-up concept and gave strain concentration factors as a function of strain range, which methodology was an extension of the one previously proposed for the SUS304 welded joint. The method predicted the uniaxial creep-fatigue life of 316FR welded joints with reasonable margins of safety.