Multiaxial life predictions in absence of any fatigue properties

Abstract

The aim of this study is to estimate fatigue life of steels and super alloys under multiaxial loading based on commonly available tensile properties. The state of loading for most components and structures is multiaxial resulting from multidirectional loading or stress concentrations. Multiaxial fatigue models have been developed to predict fatigue behavior under multiaxial loading. These models relate multiaxial stress/strain components to uniaxial fatigue properties in order to predict fatigue life. In this study, Muralidharan–Manson, Bäumel–Seeger, and Roessle–Fatemi prediction methods are employed to predict uniaxial fatigue properties based on simple tensile properties in the absence of any fatigue data. Appropriate multiaxial fatigue models representing the damage mechanism are then used along with the estimated uniaxial fatigue properties to predict fatigue lives under in-phase and out-of-phase multiaxial loading. Predictions are compared with experimental multiaxial data for sixteen different steels and super alloys from literature. Some approximation techniques to predict stress response for in-phase and out-of-phase loading based on simple tensile properties are also reviewed. Stress estimated based on these approximation techniques are then used in multiaxial fatigue life predictions and results are compared with experimental observations. It is concluded that fatigue life of steels and super alloys under multiaxial loading may be predicted reasonably well using appropriate damage models only requiring monotonic properties.