Abstract
Fatigue crack growth tests under multiaxial stress conditions were conducted at elevated temperature. Cyclic tension and torsion were applied to the thin-walled cylindrical specimens of SUS 304 stainless steel. By using DC electrical potential drop (PD) method, fatigue crack growth rate was quantified. Under multiaxial stress conditions, two types of fatigue crack growth were observed; "tensile type" crack, which propagates along the direction, φ, perpendicular to the maximum principal stress, σ_1 and "shear type" crack, which propagates along the direction of maximum shear stress, τ_<max>. Using the crack length projected to the φ-direction and the direction of τ_<max>, fatigue crack growth rates were evaluated by the corresponding stress intensity ranges, ΔK_<Ib> and ΔK_<Iic>, respectively. The characteristics of both type of fatigue crack were discussed.
