Evaluation of high temperature multiaxial fatigue behavior of 304 steel (2nd Reprot.)

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The authors have conducted a series of axial and torsional biaxial fatigue/creep-fatigue tests with :304 stainless steel at 550 C and obtained the following conclusions, (1)A fatigue life under nonproportional loading reduces to 1/2-1/3 of that under proportional loading. (2)The life reduction under nonproportional loading can be accouted for by path-dependent Mises type equivalent strain range. In this report, the results of creep-fatigue tests under proportional and nonproportional loading are examined. The following results were obtained. (1)A creep-fatigue life under nonproportional loading reduces to 1/2-1/5 of that under proportional loading. (2)Stress relaxation occurs towards origin proportionally (to the point where axial and torsional loads are zero) even under nonproportional creep-fatigue loading. (3)A creep-fatigue life under nonproportional loading can resonably be evaluated based on the fatigue properties and the creep properties obtained under uniaxial loading conditions, using the path dependent Mises type equivalent strain range and Mises equivalent stress.