Ratcheting Behavior of Inconel 718 at 649°C under Multiaxial Loading

Abstract

Ratcheting behavior has been investigated on Inconel 718 at 649°C under axial-torsional loading with load control. Ratcheting strain was measured to near failure cycles. The effects of loading path, magnitude of stress amplitude and mean stress on the development of ratcheting strain over the life have been studied by comparing the equivalent ratcheting strain. Ratcheting strain is found to increase with cycles in the manner similar to the creep strain under static load. Ratcheting rates are found higher for circular paths than for linear paths. More ratcheting occurs when the cyclic stress and mean stress are in the same direction. No clear relation is found between the ratcheting strain at failure and fatigue life, however fatigue life decreases as the ratcheting rate increases under the same applied stress.