fatigue analysis under variable amplitude loading using an energy parameter

An energy parameter accounting for normal and shear deformation is used to predict fatigue lives under variable amplitude multiaxial loading. Fatigue damage is computed as a function of orientation of the plane, and the maximum damage plane is considered as the critical plane. The linear damage rule is employed with rainflow cycle counting either on the shear or on the normal strain history depending on which gives more damage when evaluated individually. The method yields fatigue life correlations comparable to those by existing methods for materials failing in shear mode (S45C, SNCM439, SNCM630). However, a noticeable improvement is found for stainless steel 304 that exhibits a mixed normal and shear fracture behavior.