Fatigue Crack Growth Behavior of Membrane Material for LNG Storage Tank at Low Temperatures

J. Ocean Eng. Technol. 2000;14(1):23-28.

저온하에서 LNG저장탱크용 멤브레인재(STS 304강)의 피로균열진전거동

김철수

한양대학교 기계공학부

Keywords: LNG storage tank, Fatigue crack growth rate, stress intensity factor range, Stress ratio, Strain-induced martensitic transformation

핵심용어: LNG저장 탱크, 피로균열진속도, 응력화 대계수범위, 응력비, 변형률 유기 마르텐사이트 변태

Abstract

The fatigue crack growth behavior of the cold-rolled STS 304 steel developed for membrane material of LNG storage tank was examined experimentally at 293K, 153K and 111K. The fatigue crack growth rate(do/dN) tends to increase as the stress ratio (R) increases over the testing temperature when compared at the same stress intensity factor range($Delta$K). The effect of R on do/dN is more explicit at low temperatures than at room temperature. The resistance of fatigue crack growth at low temperatures is higher compared with that at room temperature which is attributed to the extent of strain-induced martensitic transformation at the crack tip. The temperature dependence of fatigue crack growth resistance is gradually vanished with an increase in $Delta$K which correlates with a decreasing fracture toughness with decreasing temperature. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and low temperature are mainly explained by the crack closure and the strengthening due to the martensitic transformation.