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

The Korean Society of Mechanical Engineers (대한기계학회)
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Cracking Near a Hole on a Heat- Resistant Alloy Subjected to Thermo-Mechanical Cycling

열 및 기계적 반복하중 하의 내열금속 표면 홀 주변 산화막의 변형 및 응력해석

  • Li, Feng-Xun (Dept. of Mechanical Systems Engineering, Chonnam Nat'l Univ.) ;
  • Kang, Ki-Ju (Dept. of Mechanical Systems Engineering, Chonnam Nat'l Univ.)
  • 이봉훈 (전남대학교 기계시스템공학부) ;
  • 강기주 (전남대학교 기계시스템공학부)
  • Received : 2010.05.13
  • Accepted : 2010.06.17
  • Published : 2010.09.01
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Abstract

In the hot section of a gas turbine, the turbine blades were protected from high temperature by providing a thermal barrier coating (TBC) as well as by cooling air flowing through internal passages within the blades. The cooling air then passed through discrete holes on the blade surface, creating a film of cooling air that further protects the surface from the hot mainstream flow. The holes are subjected to stresses resulting from the lateral growth of thermally grown oxide, the thermal expansion misfit between the constituent layers, and the centrifugal force due to high-speed revolution; these stresses often result in cracking. In this study, the deformation and cracks occurring near a hole on a heat-resistant alloy subjected to thermo-mechanical cycling were investigated. The experiment showed that cracks formed around the hole depending on the applied stress level and the number of cycles. These results could be explained by our analytic solution.

가스터빈엔진 내의 블레이드에서는 표면에 외부의 찬 공기를 흘려주는 작은 냉각 홀들을 가공하고 열 차단 코팅시스템을 코팅하는 방법으로 기지금속을 고온에서 보호한다. 열 차단 코팅은 열피로 과정에서 산화막의 성장 및 접합층과 산화막의 열팽창계수의 불일치로 산화막내부에 잔류응력이 발생하며 궁극적으로 코팅층의 분리를 유발한다. 본 연구에서는 내열합금 시편 표면에 작은 홀을 가공하여 여러 가지 고온 유지 조건에서 열 및 기계적 피로 시험을 수행하여 홀 주위의 산화막의 변형을 관찰하였다. 실험결과 기계적 피로가 홀 주위의 산화막의 변형에 중요한 영향을 미치며, 동일한 산화막 두께에서 고온 유지 시간이 짧을수록 변형이 쉽게 발생 하였다. 또한 본 연구에서는 홀 주위 산화막의 응력해석을 위한 이론적인 연구도 시도되었다.

Keywords

References

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