Several of the structural components in the superconducting magnet system for the International Thermonuclear Experimental Reactor (ITER) experience pulsed, multiaxial loading during operation. For components, such as the conductor conduits, with a large population of initial flaws, fatigue crack growth analysis (FCGR) is used to evaluate failure. For other, simpler, unwelded components, such as pins and bolts in the Central Solenoid assembly, in which flaw crack initiation is a dominant factor, S/N data can be used. However, since S/N data is available only for uniaxial load conditions, a reliable design code for multiaxial fatigue is necessary. The problem is that none of the existing design codes gives a complete definition for the equivalent mean stress in multiaxial fatigue. This paper reviews the existing theories and design codes in multiaxial fatigue, and proposes a general definition of equivalent mean stress for multiaxial fatigue for the design of ITER and other pulsed structures with multiaxial loads
