Creep rupture life and damage evaluation under multiaxial stress state for type 304 stainless steel

The biaxial creep damage of type 304 stainless steel is studied at 973 K. Biaxial tension creep tests were carried out using cruciform specimens under the principal stress ratio (λ) of 0 ≦ λ ≦ 1, where the principal stress ratio is the ratio of y-directional principal stress to x-directional stress in the gage part of the specimen (λ = σy/σx). Creep rupture times under biaxial stress conditions were shorter than those in uniaxial conditions at the same von Mises equivalent stress. Earlier void nucleation and faster void growth were observed in creep tests at larger principal stress ratio tests. Creep rupture times in biaxial stress states were discussed in relation to the void observations.