Jsub(Ic) calculations for pressure vessel steel from microvoid kinetics

The tensile fracture process in A533B steel at 366 K was studied at the microlevel and found to consist of the nucleation, growth, and coalescence of voids. A computational model of the process was constructed, and the void size distributions, measured in the necked regions of tensile bars, were used to quantify the model. The model was then incorporated into a finite-difference Lagrangian stress wave code to simulate the fracture toughness testing of a hypothetical center-cracked panel. Calculated values for Jsub(Ic), the critical crack opening angle, and the critical crack opening displacement only slightly exceeded values typically measured, demonstrating that a route now exists for calculating fracture toughness from microvoid kinetics data. Potential applications of such models include monitoring radiation embrittlement in nuclear reactor components from tests on small surveillance specimens, predicting failure in structural elements that do not already contain a macrocrack, and explaining variations in toughness and strength caused by variations in inclusion size distribution. (Auth.)