抄録
The microcrack growth law-oriented approach developed in a previous paper is applied to examine the fatigue strength and mechanism of 200 mm and 100 mm thick forged steel plates. Low-cycle fatigue tests are conducted on specimens sliced in the transverse (T) and thickness (S) directions of the plates. Through continual observation of the fatigue process, the effect of elongated inclusions on microcrack initiation and propagation behaviors is elucidated. The fatigue life is shorter in the S than in the T direction. The fatigue lives in both directions are evaluated on the basis of the microcrack propagation law. The elongated inclusions hardly affect the fatigue process in the T direction, while they show a strong influence in the S direction. The fatigue process is dominated by a monotonous growth of a leading crack in the T direction. On the contrary, the leading crack growth in the S direction is governed by a joining of subcracks.
