引張－ねじり型多軸負荷におけるSUS304 鋼のクリープ変形 およびクリープ破断寿命評価

抄録

This study investigates the multiaxial creep rupture life and creep properties of Type 304 austenitic stainless steel by conducting multiaxial creep tests at 923 K. As a multiaxial testing method, axial load and torsional torque were applied to a hollow cylindrical specimen using a combined tension-torsion testing machine. The time-strain curve was consistent up to about 10%, using the equivalent von Mises strain, independently of the difference in the multiaxial stress conditions. The creep rupture life in the pure torsion was longer than that in tensile testing, which may be because the specimen cross-sectional area remained almost unchanged in the pure torsion. The multiaxial creep rupture lives are evaluated to be within a factor of 2 scatter band using the equivalent von Mises stress which has the lowest scatter among the stress parameters. The observations of the longitudinal microstructure after the creep test showed that the crystal grains were deformed in the principal stress direction with the creep duration. In this experimental condition, the fracture was dominated by stress deformation, and the equivalent von Mises type would have been appropriate for creep deformation analysis.