Novel non-linear relationship to evaluate the critical plane orientation

Damage in offshore structures is mainly due to fatigue multiaxial stress state at structural joints, and fatigue strength assessment of such joints through the critical-plane criterion is well-accepted by the scientific community. A novel relationship to estimate the critical plane orientation is proposed in the present paper. Such a relationship is implemented in the stress-based critical-plane criterion by Carpinteri et al., which is applicable to any metallic material under multiaxial constant amplitude fatigue loading. Fatigue life of specimens made of different metallic materials is herein evaluated by using such a criterion. The experimental fatigue life of each specimen examined is compared with the analytical one. The relationship above seems to be a useful tool for estimations of fatigue life under multiaxial loading.