Special Features of Strain and Fracture in Steels under Impact Fatigue Loading

Processes of carbon steels fracture under their repetitive dynamic loading according to the compression scheme have been studied. It has been ascertained that the main cause of fracture of cyclically compressed specimens is crack initiation and propagation on exposure to tensile internal stresses forming at the crack tip during the external load removal stages. The crack growth rate is maximal at the initial stage of its advancement near the notch. When the crack propagates depthward the specimen, its rate decelerates and weakly depends on the current specimen cross section. A model of the steels fatigue fracture process under repetitive dynamic loading has been proposed. It has been revealed that medium- and high-carbon steels quenched and tempered at 300 degrees C have long life duration.