115 MPa水素ガス中におけるSCM435の水素誘起き裂進展下限界<i>K</i>_I,Hを求める試験方法

<p>To establish the test methods for obtaining threshold of hydrogen-induced crack growth, <i>K</i>_I,H, constant load, constant displacement and <i>J</i>_IC tests, and <i>J</i>_IC test without unloading were conducted on SCM435 in 115 MPa hydrogen gas. Constant load and constant displacement tests are standardized by ASME KD-10. Especially, the test duration of ferritic steels such as SCM435 is at least 1000 hr. <i>J</i>_IC test is standardized by ASTM E1820. <i>J</i>_IC test without unloading is monotonically-rising-displacement test where unloading processes are eliminated in <i>J</i>_IC test. All four tests were done under the small scale yielding in 115 MPa hydrogen gas. However, <i>J</i>_IC test was not realized, because CT specimen failured before the first unloading process. <i>K</i>_I,H of other three tests was almost the same. From viewpoints of test duration and number of specimens, <i>J</i>_IC test without loading was the best test method for <i>K</i>_I,H in 115 MPa hydrogen gas. On the other hand, <i>J</i>_IC test was the only test method for fracture toughness, KIC, in air , because KIC was obtained under the large scale yielding.</p>