압력용기용 강의 저온 피로 크랙 하한계 특성에 관한 연구(I)

A Study of Fatigue Crack Threshold Characteristics in Pressure Vessel Steel at Low Temperature

  • 박경동 (부경대학교 기계.자동차공학부) ;
  • 노태영 (부경대학교 기계.자동차공학부) ;
  • 김영대 (부경대학교 기계.자동차공학부) ;
  • 김형자 (부경대학교 기계.자동차공학부) ;
  • 오명석 (부경대학교 기계.자동차공학부) ;
  • 이경렬 (부경대학교 대학원) ;
  • 김정호 (부경대학교 대학원)
  • 발행 : 2000.02.28

초록

In this study, CT specimens were prepared from ASTM SA516 Gr. 70 which was used for pressure vessel plates for room and low temperature service. And we got the following characteristics from fatigue crack growth test carried out in the environment of room and low temperature at $25^{\circ}C,\;-60^{\circ}C,\;-80^{\circ}C\;and\;-100^{\circ}C$ and in the range of stress ratio of 0.05 by means of opening mode displacement. At the constant stress ratio, the threshold stress intensity factor range ${\Delta}K_{th}$ in the early stage of fatigue crack growth (Region I) and stress intensity factor range ${\Delta}K$ in the stable of fatigue crack growth (Region II) was increased in proportion to descend temperature. It assumed that the fatigue resistance characteristics and fracture strength at low temperature is considerable higher than that of room temperature in the early stage and stable of fatigue crack growth region. The straight line slope relation of logarithm $d{\alpha}/dN\;-{\Delta}K$ in Region II, that is, the fatigue crack growth exponent m increased with descending temperature at the constant stress ratio. It assumed that the fatigue crack growth rate $d{\alpha}/dN$ is rapid in proportion to descend temperature in Region II and the cryogenic-brittleness greatly affect a material with decreasing temperature.

키워드