Effect of prior ductile tearing on cleavage assessment for high-strength steel under mixed-mode I and II conditions

This paper calibrates the Weibull stress parameters in mixed-mode cleavage fracture for four-point bend and shear fracture specimens. The calibration approximates the prior ductile tearing in the Weibull stress without the need to simulate crack extensions in numerical analyses. This work develops the cumulative Weibull stress by assuming a steady-state fracture process zone along the experimentally measured tearing angle. The calibrated Weibull stress model, using the coplanar energy release rate criterion and the maximum principal stress criterion, leads to close estimation of the failure probability for the high-strength steel S550 under a mixed-mode I and II condition at −90 °C.