MIXED MODE (I + III) FATIGUE THRESHOLDS IN A FORGING STEEL

Abstract

Abstract— The results of mixed mode (I + III) fatigue tests on a low pressure steam turbine rotor steel are presented. Tests were performed on a uniaxial servohydraulic fatigue machine fitted with a torsion‐bending loading frame. The onset of failure was marked by fatigue facets which grew perpendicular to the maximum principal stress direction. A criterion for mixed mode (I + III) fatigue thresholds based on the orientation and the crack opening displacement of fatigue cracks is proposed.