限界ストレッチゾーン幅と引張特性を用いたオーステナイト系ステンレス鋼の破壊じん性評価

概要

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Austenitic stainless steel has high fracture toughness. Generally, large CT specimen over 1.5TCT is needed to obtain valid elastic-plastic fracture toughness, JIC, due to the high toughness. The good relationship between JIC and stretched zone width was reported, however, the application was considered to be restricted to the case of large specimen which satisfied plane strain condition. In this study, in order to obtain the similar value of JIC in the case of small CT specimen which was judged invalid in ASTM E1820, adding the tensile properties as parameter to JIC estimation was tried. JIC tests of SUS304 and SUS316L were performed according to ASTM E1820-06 with varying the parameter of the cold-work degree and specimen size. Specimen size, stretched zone width, tensile properties and JQ were analyzed, and the model to estimate valid JIC from JQ was proposed. Regression analysis was carried out using the parameter of stretched zone and tensile properties. Based on the proposed equation, JIC was successfully estimated from JQ with the small deviation within 10% in all size of CT specimen.