Abstract
This paper presents the notch effect in low cycle fatigue of Mod.9Cr-1Mo steel under multiaxial loading. Tension–torsion multiaxial low cycle fatigue tests were performed using three types of circumferential notched specimens of the steel and crack initiation, failure and propagation lives were experimentally obtained. Two proportional and nine nonproportional strain waveforms were used in low cycle fatigue tests. The superposition of torsion loading on tension loading reduced the three lives but they little decreased with elastic stress concentration factor. The three lives in nonproportional loading were smaller than those in proportional loading but showed smaller reduction with elastic stress concentration factor. Local strains at the notch root were estimated by finite element analyses and Neuber's rule. Mises strain range and maximum principal strain range conservatively estimated the crack initiation lives of the notched specimens.