Analysis of the fracture kinetics and mechanisms of 20GL steel having different strengths using the acoustic emission parameters

A joint analysis of acoustic emission pulse amplitudes, deformation diagrams, and fracture surfaces is used to study the fracture kinetics and mechanisms of 20GL steel specimens having different hardnesses and cut from the upper fragment of a freight bogie solebar. The fracture of the steel specimens subjected to normalizing and having a uniform strength and ductility over the entire cross section proceeds continuously. The crack that nucleated in the specimens with a gradient strength distribution over the cross section after volume–surface quenching slows down in a layer of a variable strength and ductility and stops in a ductile core. The crack sizes are determined from the measured peak amplitudes of acoustic emission.