溶接構造用鋼の引張破壊挙動における衝撃速度の影響

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Mechanical properties of a weldable structural steel (JIS SM41A) have been studied over wide ranges of the nominal strain rate from 3.79 × 10^<-4> to 1.82 × 10^3 sec^<-1>, and the testing temperature from 79℃ to -196℃. The fracture behavior of round bar and circumferentially notched bar specimens was studied through tensile properties, crack opening displacement (COD), notch sensitivity ratio, and fractography. Fracture stresses of circumferentially notched bar specimens pulled at tensile rates of less than 0.5mm/min showed a continuous decrease at temperatures ranging from -196℃ to 20℃. While at rates between 5 to 200 mm/min, transition behavior of fracture stress was observed against the temperature, and dynamical pulling transferred the transition temperature to the higher. In the finite element analysis, the position where the longitudinal stress, σ_z took on maximum value came closer to the notch root with the increase of the ratio of the net stress to yield stress. The ratio of critical COD to yield stress, Φ/σ_y was illustrated by one curve on both static and dynamic tests to the normalized stress. The values of Φ/σ_y from the experiment was the largest in comparing the results calculated with both finite element method and BCS model. The discrepancy among these results was discussed. The notch sensitivity ratio (NSR) generally decreased to less than unity with decrease of temperature and increase of tensile speed. However, because of the elastic constraint effect of the notch, NSR in this paper is larger than unity for almost whole region of temperature and tensile speed.
独立行政法人海上技術安全研究所の論文
1976-03-20

溶接構造用鋼の引張破壊挙動における衝撃速度の影響

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