A Study on Fatigue Crack propagation Behavior of Pressure Vessel Steel SA516/70 at High Temperature

J. Ocean Eng. Technol. 2001;15(2):105-110.

압력용기용 SA516/70 강의 고온피로균열 진전거동에 대한 연구

박경동,김정호,윤한기,박원조

부경대학교 기계공학부,부경대학교 대학원 기계공학과,동의대학교 기계산업시스템공학부,경상대학교 기계수송공학부

Keywords: Crack propagation rate, High temperature, Stress ratio, da/dN -$Delta$K, Crack closure

핵심용어: 피로균열진전속도, 고온, 응력비, 균열진전속도와 응력확대계수범위, 균열닫힘

Abstract

The fatigue crack propagation behavior of the SA516/70 steel which is used for pressure vessels was examined experimentally at room temperature, 150$^{circ}C $, 250$^{circ}C $ and 370$^{circ}C $ with stress ratio of R=0.1 and 0.3. The fatigue crack propagation rate da/dN related with the stress intensity factor range $Delta K$ was influenced by the stress ratio within the stable growth of fatigue crack(Region II) with an increase in $Delta K$. The resistance to the fatigue crack growth at high temperature is higher in comparison with that at room temperature, and the resistance attributed to the extent of plasticity-induced by compressive residual stress according to the cyclic loads. Fractographic examinations reveal that the differences of the fatigue crack growth characteristics between room and high temperature are mainly explained by the crack closure and oxide-induced by high temperature.