A New Multiaxial Fatigue Life and Crack Growth Rate Model for Various In-Phase and Out-of-Phase Strain Paths

摘要

A new multiaxial fatigue parameter for in-phase and out-of-phase straining is proposed. The parameter proposed is the sum of the normal energy range and the shear energy range calculated for the critical plane on which the stress and strain Mohr's circles are the largest during the loading and unloading parts of a cycle. The normal and shear energies used in this parameter are divided by the tensile and shear fatigue properties, respectively. The proposed parameter, unlike many other parameters, does not use an empirical fitting factor. The proposed parameter successfully correlates multiaxial fatigue lives for: (a) various in-phase and out-of-phase multiaxial fatigue straining conditions, (b) tests in which a mean stress was applied normal to the maximum shear plane, and (c) out-of-phase tests in which there was additional hardening. An effective (closure free) intensity factor range, ΔK_(eff), was derived based on the proposed parameter. This effective intensity factor successfully correlated the closure-free crack growth rates for straining of various biaxial strain ratios.