A new multiaxial fatigue model considering the influence of tensile dwell time

The influence of tensile dwell time on fatigue was usedto define a CFI (Creep -Fatigue Interaction) factor, that characterizesthe nonlinear interaction of creep damage and fatigue damage. A hightemperature multiaxial fatigue model with energy-type parameters based on thecritical plane approach was proposed. The model considers both theexperimentalobservation of fatigue fracture and the tensile dominant effects of crackinitiation, propagation and fracture under biaxial fatigue loading. Themodel has a ``unified'' ability of modeling the multiaxial fatigue lifeunder different temperatures, various loading properties and dwell time. Thematerial life constants in the model are temperature-independent andloading-independent, and the method may be generalized to other dominanteffects of fatigue to build multiaxial fatigue models. The constantsfor Udimet720 Li, a superalloy used for turbine disc, were obtained byfitting the test data under uniaxial low cycle fatigue loading with dwelltime. The model was applied to predict the fatigue life of cruciform underbiaxial cyclic loading with dwell time at elevated temperatures based on thestress-strain results by a viscoplastic finite element analysis method.Errors are within a factor of 2, that is, within the engineeringrequirement margins. The validity and accuracy of the model were verified.