A new multiaxial fatigue model considering the influence of tensile dwell time
一种考虑拉伸保持效应的多轴疲劳寿命模型

The influence of tensile dwell time on fatigue was used to define a CFI (Creep -Fatigue Interaction) factor, that characterizes the nonlinear interaction of creep damage and fatigue damage. A high temperature multiaxial fatigue model with energy-type parameters based on the critical plane approach was proposed. The model considers both the experimental observation of fatigue fracture and the tensile dominant effects of crack initiation, propagation and fracture under biaxial fatigue loading. The model has a "unified" ability of modeling the multiaxial fatigue life under different temperatures, various loading properties and dwell time. The material life constants in the model are temperature-independent and loading-independent, and the method may be generalized to other dominant effects of fatigue to build multiaxial fatigue models. The constants for Udimet720 Li, a superalloy used for turbine disc, were obtained by fitting the test data under uniaxial low cycle fatigue loading with dwell time. The model was applied to predict the fatigue life of cruciform under biaxial cyclic loading with dwell time at elevated temperatures based on the stress-strain results by a viscoplastic finite element analysis method. Errors are within a factor of 2, that is, within the engineering requirement margins. The validity and accuracy of the model were verified.