Near-Threshold Fatigue Crack Growth Behavior at High Temperature in a Vacuum in SUS304
Masahiro TSUJI, Akira SATO, Tokutsugu MINAMI, Kota IMANISHI and Shiro KUBO
Abstract:Fatigue crack growth tests were conducted for SUS304 stainless steel in the near-threshold region using single-edge-cracked (SEC) specimens at 350, 550 and 650 in a vacuum. Crack growth behaviors of SUS304 in a vacuum were compared with those in air to investigate the effect of the environment and oxidation on the behavior of fatigue crack growth in the near-threshold region. It was found that threshold value, ’Kth, was higher than that in air, and that ’Kth at high temperatures reached a maximum value at about 550. When the value of Kmax was increased in a threshold condition obtained by using the conventional ’K-decreasing test, crack growth was observed for ’K lower than the conventional threshold. Crack growth was also observed after successive increase in Kmax in the newly established subthreshold region in a vacuum as well as in air. In the region below a certain value of ’K, however, crack no longer grew even after the change of Kmax at 550. Discussion was made on the characteristics of the fatigue crack growth threshold. Key Words:Fatigue crack growth, Fatigue threshold, High temperature, In a vacuum, SUS304 stainless ste