Strength Characteristic of SUS316 and STPT410 Steels under Cyclic Overloading with Pre-Cracked in Non-Proportional Multiaxial Fatigue

Abstract

The actual structures receive not only proportional loading (tension and compression loading) but also non-proportional loading in which principal directions of stress and strain are changed depending on time. In the researches for multiaxial non-proportional cyclic loading tests, it has been reported that number of crack initiation cycles is decreased and number of cracks is also significantly increased under multiaxial non-proportional loading compared with those in proportional loading. It also has been reported that an additional hardening occurs due to the non-proportional loading which leads to additional interaction between slip systems resulted from increase in active slip systems under non-proportional loading. In the present study, cyclic overloading tests were carried out on SUS316 and STPT410 steels, in which the cyclic overloads were applied after pre-crack fatigue tests under proportional and non-proportional loading. The effects of pre-crack loading under non-proportional loading on the deformation and fracture characteristics under cyclic overloading are discussed.