Host: The Japan Society of Mechanical Engineers
Name : [in Japanese]
Date : September 08, 2024 - September 11, 2024
There have been many studies on low-cycle fatigue of steel under axial loading, such as quantitative studies on small crack propagation and studies on the effect of grain size on fatigue strength. However, in the case of low-cycle fatigue of steel in torsion, there are not many studies that quantitatively evaluates crack propagation and examines the effect of grain size, although there are some studies that continuously observe crack initiation and propagation. In this study, cyclic torsional low-cycle fatigue tests were performed on S10C specimens with different grain sizes, and the effect of grain size on small crack propagation and the validity of the small crack propagation law in torsional low-cycle fatigue were investigated, focusing on cracks with lengths up to 1 mm. Fatigue tests were conducted in a torsion testing machine (490 Nm capacity) at room temperature in air and controlled torsional angle for a given total strain range. Cracks were observed using the replica method, and replicas of the specimen surface were taken at regular intervals in each total strain range and observed with an optical microscope. The results showed that the small crack propagation law was established in torsional low-cycle fatigue, and that the larger the grain size, the shorter the crack propagation life.
