Since fast reactors are designed with thin-walled structures and the operating temperature exceeds the creep temperature, it is important to understand the creep characteristics. The rules on Fitness-for-Service of the JSME specify criteria for coalescence of multiple proximate cracks in fatigue and stress corrosion cracking environments. However, the coalescence behavior of crack growth in a creep environment is not clear. Therefore, fatigue and creep crack growth tests were conducted using SUS304 flat plates with through-wall cracks introduced in several different planes. Fatigue crack growth tests showed that the cracks grew horizontally, overlapped, and then began to grow toward the other crack. In the creep crack growth test, the crack grew horizontally as in the fatigue crack growth test, but they fractured due to plastic collapse before the cracks overlapped. The propagation behavior of fatigue cracks and creep cracks showed the same uncoalescing behavior for both, as far as could be confirmed.
HORIO et al. (Wed,) studied this question.