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

The Korean Society of Mechanical Engineers (대한기계학회)
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Creep-Fatigue Life Design with Various Stress and Temperature Conditions on the Basis of Lethargy Coefficient

응력 및 온도 변화시 무기력계수를 이용한 크리프-피로 수명설계

  • Park, Jung-Eun (Dept. of Mechanical System Engineering, Chonbuk Nat'l Univ.) ;
  • Yang, Sung-Mo (Dept. of Mechanical System Engineering, Chonbuk Nat'l Univ.) ;
  • Han, Jae-Hee (Dept. of Mechanical System Engineering, Chonbuk Nat'l Univ.) ;
  • Yu, Hyo-Sun (Dept. of Mechanical System Engineering, Chonbuk Nat'l Univ.)
  • 박정은 (전북대학교 기계시스템공학부) ;
  • 양성모 (전북대학교 기계시스템공학부) ;
  • 한재희 (전북대학교 기계시스템공학부) ;
  • 유효선 (전북대학교 기계시스템공학부)
  • Received : 2010.07.05
  • Accepted : 2010.12.16
  • Published : 2011.02.01
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Abstract

High temperature and stress are encounted in power plants and vehicle engines. Therefore, determination of the creep-fatigue life of a material is necessary prior to fabricating equipments. In this study, life design was determined on the basis of the lethargy coefficient for different temperatures, stress and rupture times. SP-Creep test data was compared with computed data. The SP-Creep test was performed to obtain the rupture time for X20CrMoV121 steel. The integration life equation was considered for three cases with various load, temperature and load-temperature. First, the lethargy coefficient was calculated by using the obtained rupture stress and the rupture time that were determined by carrying out the SP-Creep test. Next, life was predicted on the basis of the temperature condition. Finally, it was observed that life decreases considerably due to the coupling effect that results when fatigue and creep occur simultaneously.

발전설비 및 자동차의 엔진에서 고온과 응력이 발생하므로 안전을 위하여 제품을 생산하기 전에 재료의 수명설계가 필요하다. 본 연구에서는 온도, 응력, 파단 시간으로 이루어진 무기력계수를 이용하여 수명설계를 수식화하였다. 통합수명식을 이용하여 SP-Creep 시험 데이터와 계산된 데이터를 비교하였다. SP-Creep 시험은 X20CrMoV121강의 파단시간을 획득하기 위하여 수행하였고 수명설계식을 통해 하중, 온도, 하중-온도가 작용하는 3가지 경우를 고려하였다. 첫째로, 무기력계수는 SP-Creep 시험에서 획득한 파단응력과 시간에 의해 계산하였다. 두 번째로, 온도 조건을 주어 수명을 예상하였다. 세 번째로, 부재는 피로와 크리프가 동시에 작용할 때 커플링 효과 때문에 더 열악한 상태에 놓이게 된다. 수명은 커플링 효과 때문에 현저하게 감소하는 것으로 나타났다.

Keywords

References

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