Biaxial Fatigue of A533B Pressure Vessel Steel

The low-to-intermediate cycle fatigue behavior of A533B steel is investigated using solid round bar specimens tested in combined bending and torsion. Loadings are applied in-phase and 90 deg out-of-phase to produce cases of proportional and nonproportional biaxial fatigue. Out-of-phase loadings are found to be more damaging than in-phase loadings. Two equivalent strain criteria similar to those in the ASME Boiler and Pressure Vessel Code and a newer approach based on cyclic plastic work are used to correlate fatigue lives. The equivalent strain criteria are found to underestimate the fatigue damage in out-of-phase tests, but to provide reasonably good correlations overall. The plastic work approach provides a conservative treatment of the out-of-phase data and somewhat better overall correlation. Cracking behavior observed during the tests is also summarized.