| 摘要 |
PROBLEM TO BE SOLVED: To provide a method by which the fatigue crack developing speed of a steel product can be evaluated quickly and efficiently. SOLUTION: The ductile crack development resistance of the steel product after a prestrain of±ε% is loaded N cycles to the product is evaluated on an R curve which is expressed by the CTOD specified by the formula of (CTOD)=C×(Δa)<n> . In the formula, the CTOD andΔa respectively denote the crack tip opening displacement (mm) and the grown length of a ductile crack (mm) and C and n respectively denote a coefficient and an index. Theε, N, and n can be set at 2, 20, and 0.7, respectively.
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