Spectral fatigue life estimation for non-proportional multiaxial random loading

• A frequency-domain High-Cycle Fatigue critical plane-based criterion is presented.
• Fatigue life of smooth structures under multiaxial random loading is estimated.
• The PSD function of an equivalent normal stress quantifies the fatigue damage.
• Influence of the critical plane orientation on fatigue life estimation is evaluated.
• Multiaxial random fatigue test data are compared with the theoretical results.

A frequency-domain High-Cycle Fatigue (HCF) criterion based on the critical plane approach is here proposed to estimate fatigue life of smooth metallic structural components under multiaxial random loading. The procedure consists of the following three steps: (a) definition of the critical plane; (b) PSD evaluation of an equivalent normal stress; and (c) computation of the fatigue life. A new formulation to define the critical plane is adopted in order to improve the lifetime estimation. The criterion is validated through comparison of the obtained numerical results with experimental fatigue data available in the literature for structural steel specimens subjected to a combination of random non-proportional bending and torsion.