Fracture Mechanics Analysis of a Crack in the Weld using the J-integral

J-적분을 이용한 용접접합부 균열의 파괴 역학적 해석

  • 장경호 (중앙대학교 건설환경공학과) ;
  • 이진형 (중앙대학교 기술과학연구소)
  • Received : 2004.10.15
  • Accepted : 2005.02.04
  • Published : 2005.04.27

Abstract

The fracture mechanics analysis of a crack in a weld must consider residual stress generated during welding. The standard definition of the J-integral requires a path dependent value in the presence of a residual stress field. Therefore, it is necessary to develop a path independent J-integral definition for a crack in a residual stress field. This paper addresses the modification of the Rice-J-integral to produce a path- independent J-integral when residual stresses and external forces are present. The residual stress problem is treated as an initial strain problem and the J-integral proposed for this type of problems is used. A program which can evaluate the J-integral for a crack in a weld is developed using the proposed J-integral definition. The situation when only residual stress is present is examined as is the case when mechanical stresses are applied in conjunction with a residual stress.

용접접합부 균열의 파괴 역학적 해석을 위해서는 용접 중에 발생하는 잔류응력을 고려하여 해석이 수행되어야 한다. 잔류응력이 존재하면 J-적분은 더 이상 적분경로에 관계없이 일정한 값을 갖는 특성을 잃어버리게 된다. 그러므로 용접접합부 균열의 J-적분 해석을 위해서는 잔류응력이 존재하는 경우에도 적분경로에 관계없이 일정한 값을 갖는 새로운 J-적분식이 도입되어야 한다. 따라서 본 연구에서는 기존의 J-적분을 수정하여 잔류응력이 존재하는 경우에 경로 독립성을 유지하는 J-적분을 고찰하고, 이를 이용하여 잔류응력과 외력이 동시에 작용하는 균열선단에서의 J-적분을 해석할 수 있는 프로그램을 개발하였다. 자체개발한 탄소성 해석 프로그램을 이용하여 용접 시 잔류응력과 외력에 대한 응력분포를 계산하였으며, 이를 이용하여 잔류응력과 외력의 복합하중에 대한 J-적분을 계산하였다.

Keywords

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