Pressure vessel steels crack driving force assessment using different models

Fracture behavior of two pressure vessel steels, 20MnMoNi55 and 50CrMo4, was numerically investigated in this work. The research was conducted using numerical models of single-edge notched bend (SENB) and disk compact type (DCT) specimens. J-integral, an important fracture mechanics parameter, was chosen as a criterion for the fracture behavior comparison of two mentioned steels. J-integral values were determined using newly developed numerical algorithm coupled with finite element (FE) analysis. Numerically obtained J-integral values are presented as a measure of crack driving force versus crack growth size (Δa) for a range of initial crack sizes (a/W = 0.25, 0.375, 0.5, 0.625). Fracture behavior of two steels was investigated using numerical models of pressure vessels containing also inner axial crack of different sizes (a/t = 0.25, 0.375, 0.5, 0.625). Although J-integral values cannot be transferred from specimens to real structures, results obtained on pressure vessels have proved useful in engineering assessment of fracture behavior of such structures.

► Pressure vessel materials (20MnMoNi55, 50CrMo4) fracture behavior comparison. ► Algorithm for J-integral calculation. ► FE analysis of SENB specimen. ► FE analysis of uncracked and cracked pressure vessels. ► Strain measurements of uncracked and cracked pressure vessels.