DAMAGE ACCUMULATION MODE FATIGUE CRACK PROPAGATION AND PROPAGATION BEHAVIOR PREDICTION METHOD
Shigeru HamadaGrand Ballroom B
To achieve high-strength steels, their microstructures are complicated. However, with effort, these high-strength steels do not exhibit the fatigue limits expected from their hardness or tensile strength. The low fatigue limit due to inclusions in the steels can be predicted as a fatigue limit problem for metallic materials with small defects. However, the threshold stress intensity factor range of high-strength steel of a long crack is still not as high as expected from the hardness. Currently, there is no clear explanation for this reason. Therefore, the material cannot be used with confidence. The authors propose that this is due to a different crack extension mechanism. In other words, the authors point out the existence of a different mechanism of fatigue crack extension from the generally accepted mechanism of fatigue crack extension due to plastic deformation by alternating slip. Based on the mechanism, the mode of fatigue crack extension is called damage accumulation mode fatigue crack propagation. This name differs from the conventional name focusing on the loading mode, i.e., Modes I, II, and III, and is focused on the extension mechanism. This study discusses a method to predict the fatigue crack propagation behavior.