Study on Brittle Fracture Toughness Decrease due to High Strain Concentration of 9% Nickel Steel inner Shell Plate at LNG Aboveground Storage Tank

Abstract

Recently, many papers have reported on a decrease in brittle fracture toughness that steel structures suffer after a strong earthquake. Thus, it is necessary to evaluate the structural integrity of 9% nickel steel tanks under high strain concentration. In this study, the 3-point bend CTOD testing of 9% nickel base metal and welded joints was carried out at LNG temperature. The effect of pre-strain and high-speed strain on the critical CTOD was experimentally investigated. Based on fracture mechanics, it was confirmed that cracks in welded joints would not be propagate from defects detectable by non-destructive inspection, in the event of high-speed strain after plastic pre-strain during a strong earthquakes.