Relationship Between Small Crack Propagation Properties and Manson-Coffin's Rule in Low Cycle Torsional Fatigue

Abstract

A low cycle torsional fatigue test of carbon steel S10C for machine structural use was performed with strain control. Using a mechanism that applied Martens's mirror device, the scale was read, and the torsional torque was increased or decreased to achieve a predetermined torsional angle, and experiments were performed with total strain widths γ = 1.0%, 1.5%, and 2.0%. As a result, the propagation behavior of cracks in low cycle torsional fatigue was connected and propagated by innumerable microcracks. The fatigue life calculated by the small crack propagation law, focusing on the main crack that caused the fracture, was equivalent to the fatigue life of the Manson-Coffin’s law.