Fracture toughness analysis of a ductile steel by means of 3D surface displacements

► Standard fracture toughness tests were done on a ductile steel. ► In situ monitoring of 3D surface displacements was done using DIC technique. ► The onset of stable crack growth was inferred from out-of-plane displacements. ► New approach to fracture toughness testing of ductile materials was investigated.