Investigation on micromechanism and stress state effects on cleavage fracture of ferritic-pearlitic steel at-196 °C

Mechanical tests of a ferritic-pearlitic steel were conducted at -196 degrees C with various specimen geometries resulting in different stress states. Elastic-plastic finite element method (FEM) simulations were used to analyze the local stress and strain distributions of the studied steel. It is found that cementite lamellae are the initiation sites for cleavage fracture. In addition, the cleavage fracture critical stage and the local equivalent plastic strain at initiation site varies with stress triaxiality and Lode angle.