The Effect of Inclusions on the Torsional Fatigue of Anisotropic Rolled Steel : Examinations Based on Successive Observation of Specimen Surface

摘要: Torsional fatigue tests were carried out, after electropolishing the specimens cut out of a rolled steel in rolling, thickness and 45° directions. The processes observed successively by metallurgical microscope. main results obtained are as follows : 1) torsional limit each directional specimen is always controlled limiting conditions for propagation cracks occurring from inclusions. 2) inclusions initiated within first 5 % lifetime specimen. 3) In both bending fatigues, effect on strength small bar-shaped inclusions, but large circular-plate shaped 4) When stress repeated specimen, length non-propagating reaches saturated value before approximately 2×106 cycle repetitions.