Fatigue crack growth under mixed mode I-II loading with a single tensile overload at negative load ratios

Fatigue crack growth (FCG) behavior under mixed mode loading has been received extensive attention, including overload condition. The mixed mode I-II fatigue crack growth behavior of commercial pure titanium (CP-Ti) with tensile overload at negative load ratios was investigated by experiment and finite element method (FEM). The effects of loading angle, load ratio and overload on mixed mode I-II fatigue crack growth were discussed with a modified compact-tensile-shear (CTS) specimen. The mechanism of mixed mode crack growth with overload was revealed. Fatigue crack growth path and fatigue crack growth rate (FCGR) with/without overload were compared experimentally, and overload retardation effect was investigated. The variation of plastic zone and the distribution of stress and strain were simulated through finite element method. The mechanism of overload retardation effect of mixed mode I-II crack growth under compressive load was illustrated by microscopic perspective, crack closure and residual compressive stress at crack tip, and the weakening effect of mode II shear component and compressive load effect on overload retardation effect was demonstrated.

Automated summary

This study investigated the mixed mode I-II fatigue crack growth behavior of commercial pure titanium (CP-Ti) under tensile overload at negative load ratios using experiments and finite element method (FEM). The effects of loading angle, load ratio, and overload on crack growth were discussed, and the mechanism of crack growth under overload was revealed. The experimentally compared fatigue crack growth path and rate with/without overload, and investigated the overload retardation effect. The variation of plastic zone and the distribution of stress and strain were simulated through FEM. The microscopic perspective, crack closure, residual compressive stress at crack tip, mode II shear component, and compressive load effect on overload retardation effect were demonstrated.