Multiaxial Low-Cycle Fatigue Damage Evaluation Using A. C. Potential Method for Alloy 738LC Superalloy

This paper studies tension/torsion multiaxial low-cycle fatigue lives and creep-fatigue damage evaluation for Alloy 738LC superalloy. Tension/torsion creep-fatigue tests were carried out using hollow cylinder specimens and multiaxial creep-fatigue lives were obtained. The Mises’ equivalent strain correlated the multiaxial low cycle fatigue lives within a factor of two scatter band. An a.c. potential method is developed to detect the creep-fatigue damage associated with crack nucleation and extension. A.c. potentials at high frequencies accurately detect the creep-fatigue damage from the early stage of life while those at low frequencies detect that in the final stage of life. A.c. potentials at high frequencies detect the crack density, defined as the total crack length per unit area, and maximum crack length more sensitively than those at low frequencies.