Features of failure with cleavage after ctod tests of low-carbon microalloyed marine steel S460MLO during crack opening tests

Using results of testing industrial batches of 23 mm thick steel heavy plates after thermomechanical rolling and subsequent post-welding heat treatment, features are analyzed for fatigue crack formation within a specimen fracture during CTOD (Crack Tip Opening Displacement) testing for fracture toughness. Visual, microstructural, and fractographic studies are conducted on the nature of fracture formation and fatigue crack propagation mechanisms. Probable causes of a potential “pop-in” effect on load-displacement diagrams of notch opening displacement are described, as well as its potentially unfavourable effect on test result interpretation.