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

The Korean Society of Mechanical Engineers (대한기계학회)
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Evaluation of Fracture Toughness of Copper Thin Films by Combining Numerical Analyses and Experimental Tests

해석과 실험을 결합한 구리 박막의 파괴인성 평가

  • Kim, Hyun-Gyu (Dept. of Mechanical and Automotive Engineering, Seoul National University of Science & Technology) ;
  • Oh, Se-Young (Dept. of Mechanical and Automotive Engineering, Seoul National University of Science & Technology) ;
  • Kim, Kwang-Soo (Dept. of Mechanical and Automotive Engineering, Seoul National University of Science & Technology) ;
  • Lee, Haeng-Soo (Mechanical Engineering, Ulsan College) ;
  • Kim, Seong-Woong (Korea Institute of Materials Science (KIMS)) ;
  • Kim, Jae-Hyun (Korea Institute of Machinery & Materials (KIMM))
  • 김현규 (서울과학기술대학교 기계자동차공학과) ;
  • 오세영 (서울과학기술대학교 기계자동차공학과) ;
  • 김광수 (서울과학기술대학교 기계자동차공학과) ;
  • 이행수 (울산과학대학교 디지털기계학부) ;
  • 김성웅 (재료연구소) ;
  • 김재현 (한국기계연구원)
  • Received : 2012.07.26
  • Accepted : 2012.09.19
  • Published : 2013.02.04
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Abstract

In this paper, a method of combining numerical analyses and experimental tests is used to evaluate fracture toughness of copper thin films of $15{\mu}m$ thickness. Far-field loadings of a global-local finite element model are inversely estimated by matching crack opening profiles in experiments with numerical results. The fracture toughness is then evaluated using the J-integral for cracks in thin films under far-field loadings. In experiments, Cu thin films attached to Aluminum sheets are loaded indirectly, and crack opening profiles are observed by microscope camera. Stress versus strain curves of Cu thin films are obtained through micro-tensile tests, and the grain size of Cu thin films is observed by TEM analysis. The results show that the fracture toughness of Cu thin films with $500nm{\sim}1{\mu}m$ sized grains is $6,962J/m^2$.

본 연구에서는 해석과 실험을 결합하여 $15{\mu}m$ 두께 구리 박막의 파괴인성을 평가하였다. 박막의 균열 진전 실험에서 관측된 영상과 동일한 균열 열림 형상을 보이는 국부-전체 유한요소 해석 모델의 원거리장 하중 조건을 역문제로 구성하여 구하게 된다. 단순화시킨 원거리장 하중 조건을 사용하여 유한요소 해석을 하였으며 균열 선단의 J-적분을 통하여 파괴인성을 평가하였다. 실험에서는 균열이 있는 구리 박막을 알루미늄 판에 붙여서 하중을 간접적으로 부여하였으며, 현미경 카메라를 사용하여 균열의 열림을 관측하였다. 마이크로 인장시험기를 사용하여 구리 박막의 응력-변형률 곡선을 구하였으며 구리 박막의 결정립 크기를 관측하기 위하여 투과전자현미경(TEM)을 사용하였다. 본 연구서는 $500nm{\sim}1{\mu}m$ 크기 결정립을 갖는 구리 박막의 파괴인성은 $6,962J/m^2$ 으로 평가되었다.

Keywords

References

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