大型鍛鋼における集合微小欠陥の破壊力学的評価法の検討

概要

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In large forgings such as turbine rotors, it is often recognized that small clustered Laws or heavy sulfide inclusions are scattered in the center part. These flaws or inclusions are too small to be evaluated individually by the linear elastic fracture mechanics (LEFM) and their scattered area is too large to be evaluated for understanding unstable fracture of the forgings. The present study was made to and out a simple way to evaluate these flaws by using the fracture toughness of matrix (K_<Ic>, J_<Ic>) and simple bending fracture tests of smooth specimens containing flaws. An equivalent crack (A_<eq>) was calculated from these tests by different methods. The equivalent single crack calculated by using J-integral was the same order as individual small flaws, while that calculated by LEFM gave the same order as the sulfur segregation band width. J_<Ic> seemed to express the initiation of unstable fracture from individual small flaws. A simpler value "f"(=√<mA_<eq>>) instead of the equivalent crack (A_<eq>) was proposed for the evaluation of these clustered flaws.
社団法人日本材料学会の論文
1984-05-15