Fatigue life evaluation of metallic structures under multiaxial random loading

A frequency-domain critical-plane criterion is reformulated in order to improve its accuracy in terms of fatigue life estimation for smooth metallic structural components under multiaxial random loading. The criterion here proposed consists of three steps: (i) definition of the critical plane; (ii) Power Spectral Density (PSD) evaluation of an equivalent normal stress; (iii) estimation of fatigue life by implementing damage models different from that used in the original formulation. Such a reformulated criterion is numerically validated by employing experimental fatigue results for 18G2A and 10 HNAP structural steels, subjected to random combined bending and torsion. Further, the above theoretical results are also compared with those determined through a time-domain criterion proposed in the past by some of the present authors.