Transactions of the Korean Society of Mechanical Engineers A (대한기계학회논문집A)

The Korean Society of Mechanical Engineers (대한기계학회)
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Fatigue Crack Growth Characteristics of Cold Stretched STS 304 Welded Joint

콜드 스트레칭 STS 304강 용접부의 저온피로균열진전 특성

  • 이정원 (충남대학교 기계공학과) ;
  • 나성현 (충남대학교 기계공학과) ;
  • 윤동현 (충남대학교 기계공학과) ;
  • 김재훈 (충남대학교 기계공학과) ;
  • 김영균 (한국가스공사 가스기술연구원) ;
  • 김기동 (한국가스공사 가스기술연구원)
  • Received : 2017.01.04
  • Accepted : 2017.05.17
  • Published : 2017.09.01
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Abstract

STS 304 steel is used as pressure vessel material, and although it exhibits excellent mechanical characteristics at a low temperature, it is heavier than other materials. To address this issue, a method using cold-stretching techniques for STS 304 can be applied. In this study, a cold-stretching part and welded joint specimen were directly obtained from a cold-stretching pressure vessel manufactured according to ASME code. Fatigue crack propagation tests were carried out at room temperature and $-170^{\circ}C$ using the compliance method for stress ratios of 0.1 and 0.5. The results indicate that crack growth rate of the welded joint is higher than that of the cold-stretching part within the same stress intensity factor range. The outcome of this work is expected to serve as a basis for the development of a cold-stretched STS 304 pressure vessel.

압력용기 재료로 사용되는 STS 304강은 저온에서 기계적 특성이 우수하지만, 다른 합금과 비교하여 중량이 무겁다. 이러한 문제를 해결하는 방안으로 STS 304강에 콜드 스트레칭(Cold stretching)공법을 사용하는 방법이 있다. 본 연구에서는 ASME 규정에 따라 제작된 콜드 스트레칭 압력용기에서 직접 채취한 콜드 스트레칭부 및 용접부 시험편을 이용하여, 상온 및 $-170^{\circ}C$에서 응력비 0.1과 0.5에 대하여 컴플라이언스법을 이용하여 피로균열진전시험을 수행하였다. 시험결과, 용접부의 피로균열진전속도는 콜드 스트레칭부에 비해 동일 응력확대계수범위에서 빠른 것을 확인하였다. 이러한 결과는 콜드스트레칭 공법을 사용하여 제작한 STS강 압력용기 개발을 위한 기초자료로 활용될 수 있을 것이다.

Keywords

References

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