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In this paper, the crack propagation behavior of naturally initiated small crack in in low-carbon/medium-nitrogen 316 stainless steel under thermo-mechanical fatigue loading was investigated. The experimental results indicated that the importance of the investigation of small crack propagation behavior because the information on the basis of physically long crack growth rate provides a dangerous evaluation on reliability to actual components. The small crack exhibits high growth rate under the In-phase TMF loading because of irreversible creep and plastic strains. However, the growth rates of small crack under the Out-of-phase TMF loading were lower because the effect of creep deformation became negligible in such condition.

Structural materials employed for high-temperature and high-hydrogen-pressure service require excellent strength, and 2.25Cr-1Mo steel is widely used for such purposes. For instance, it is used in pressure vessels employed for hydro desulfurization, hydrocracking, and coal-liquefaction units. However, instances of hydrogen-related cracks occurring during a shutdown period have been reported when 2.25Cr-1Mo steel is used for long periods at high temperatures and high hydrogen pressures. As the risk of internal hydrogen embrittlement during shutdown, along with the detrimental effect of long-term temper-embrittlement, is a particular concern for the integrity and safe operation of pressure vessels, the combined effect of temper-embrittlement and hydrogen embrittlement in Cr-Mo steels was previously investigated using a step-cooling treatment, which is an accelerated temper-embrittlement treatment. In practical usage, it is important to ascertain the threshold stress-intensity factor at the onset of hydrogen-enhanced crack growth, KIH, of the material following long-term use. In the present study, we employed the offset potential-drop method to clarify the threshold stress-intensity factor, KIH for 2.25Cr-1Mo steel that had been used in actual equipment for a period of approximately 64,000 h at service temperatures (360–440 °C).

The seven-band grouper, Epinephelus septemfasciatus (Thunberg), is currently recognized as a potential new species for aquaculture in Japan. This study describes normal and abnormal skeletal development of the jaw and vertebrae in cultured larvae and early juveniles of E. septemfasciatus. The ontogenetic stages at which skeletal deformities of jaw and vertebra developed were also described for this species. Osteological observations were made using a clearing and staining method for larvae and soft X-ray photographs for juveniles. A high incidence of skeletal deformities was observed in the jaws and vertebral column during the larval and juvenile stages. Most of the jaw deformities were explained by an abnormal maxilla curvature. Jaw deformities were visually evident from flexion stage after ossification of the deformed elements. Deformities in the vertebral column (mostly lordosis) were observed from the post-larval stage and became more evident as growth proceeded. The lordosis generally occurred on the positions of the 8–11th vertebra. These types of deformities are compared with those of other species, and possible causative factors of the skeletal deformities are discussed.