Effect of loading rate on fracture morphology in a high strength ductile steel

Fracture experiments in a high-strength ductile steel (2.3Ni-1.3Cr=0.17C) w ere conducted under static and dynamic loading conditions in a three-point bend and a one-point bend configurations. A qualitative description of the influence of loading rate on the microscopic features of the fracture surfa ces and their role in the fracture initiation process was considered. The f racture surfaces consist of tunneled region and shear lips. The size of the shear lips increases wit increasing loading rate and is characterized by m icrovoids and cell structures. The tunneled region consists of large voids and micro-voids that coalesce by impingement. At high loading rates, locali zed molten zones are observed at the tunnel-shear lip interface.