混合モードI-II負荷におけるA7075合金の破壊じん性およびSCC挙動

概要

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Under mode I, II and mixed-mode I-II loading, the fracture toughness and SCC response of aluminum alloy 7075-T6 plate have been studied in the S-L and L-S orientations. The fracture toughness in S-L under mixed-mode loading coincides with K_<1C> for K_2/K_1 <1 and K_<2C> for K_2/K_1>1, where K_<1C> and K_<2C> are the fracture toughness under mode I and mode II respectively, and K_2/K_1 is the stress intensity ratio. The former fracture occurs due to a preferential intergranular delamination controlled by a normal stress component on grain boundaries, while the latter fracture proceeds in a trangranular shear mode. The SCC growth rate under the mixed-mode loading decreases with an increase of K_2 component, and under the pure mode II loading SCC growth becomes more difficult. Based on the experimental results and discussions of stress-induced hydrogen accumulation at crack tip the intergranular SCC of 7075-T6 can assumed principally controlled by hydrogen embrittlement, and an anodic dissolution reaction involved in the mode II SCC process plays an assisting role in lamellar crack joining in transgranular fracture.
社団法人日本材料学会の論文
1996-06-15