Evaluation of the stress-strain state at the crack tip in casing pipes based on numerical simulation

The distribution of local stresses and strains in a specimen in the vicinity of the crack tip in 50G and 32G2 casing pipe steels with different microstructure is obtained by simulating the stress-strain state at the crack tip and using numerical calculations. Steels are distinguished by atypical mechanical behavior: lower-strength 50G steel with a coarse-grained ferrite-pearlite structure is characterized by lower resistance to brittle fracture compared to 32G2 steel with a fine-grained bainite structure. The finite element method is used to simulate the specimen with a crack, and for calculations the true stress-strain curves of the steels are used. The calculation results confirm a higher susceptibility of the coarsegrained steel to crack propagation by brittle fracture.