モードIとモードIIの混合モード負荷条件における薄板鋼材の延性-ぜい性遷移挙動

概要

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This paper is concerned with the ductile-brittle transition behavior in sheet specimens of carbon steels under mode I -II mixed mode loading conditions. Mixed mode tests were carried out on 1.6 mm thick center-cracked sheet specimens of S50C and HT50 under various mixed mode loading conditions in the ductile-brittle transition temperature region using the testing method proposed by the present authors. In this method, the loading condition can be varied by changing the angle between the loading direction and the crack plane. The specimen width and the crack length were also changed. From the experiments, it was shown that the fracture appearance varied with decreasing test temperature, independent of the loading direction, as follows : ( a ) a ductile crack initiates and then extends, ( b ) a ductile crack initiates and then extends as a brittle cleavage crack, and ( c ) a cleavage crack initiates and extends. The upper limit temperature below which cleavage fracture can occur showed a tendency to decrease with increasing mode II component in the case of S50C, but it was almost constant and independent of the loading direction in the case of HT50.
1992-10-25