Fatigue Crack Propagation under Biaxial Cyclic Loading Condition Containing Phase Differences

Fatigue crack propagation under biaxial tensile loading containing phase differences is highlighted in this study. Ships and offshore structures are subjected to many types of loading, e.g. wave induced forces, gravity, and inertia forces. Generally, these loadings have different axial components with different phases. However, the structural integrities of structures and vessels are evaluated according to design codes based on theoretical and experimental investigations under a uniaxial loading condition. Most of these codes are based on the S-N curves approach. An approach that does not use S-N curves has been favored by researchers, with the fracture mechanics approach preferred for evaluating the fatigue life of structures. An advanced fracture mechanics approach was developed based on the Re-tensile Plastic zone Generating (RPG) stress criterion for fatigue crack propagation. In this study, fatigue crack propagation tests under biaxial loading with four different phase conditions and two different loading components are performed and the effect of the phase difference under biaxial loading is evaluated. We present a numerical simulation method of fatigue crack propagation based on the RPG stress criterion under different biaxial loading phase conditions and the validity of our proposed method is confirmed by comparing the estimated fatigue crack propagation histories with measured data.