| 摘要 |
PROBLEM TO BE SOLVED: To provide a method which evaluates whether a member composed of a high-hardness steel generates a delayed fracture or not under a usage condition. SOLUTION: Regarding n pieces of test pieces, the minimum value of X found by Expression (1) is used as a fracture limit parameter, and it is evaluated that the delayed fracture is not generated when the value of X under the usage condition is less than the fracture limit parameter. In the expression,σeff, V0 Vf , m, Have.,γ,σh, V, R and T respectively represent a maximum main stress, the basic volume of a fracture, the process zone of the fracture, a constant, a diffusible hydrogen concentration in the steel, the ratio of hydrogen to the effect of a stress with reference to the fracture, a hydrostatic pressure stress, the molar volume of the hydrogen, a gas constant and an absolute temperature.
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