Journal of the Computational Structural Engineering Institute of Korea (한국전산구조공학회논문집)

Computational Structural Engineering Institute of Korea (한국전산구조공학회)
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Development of Computational Evaluation Method for Fatigue Crack Growth Rate based on Viscoplastic-Damage Model

점소성-손상모델 기반 피로균열 진전속도 전산 평가법 개발

  • Kim, Seul-Kee (Departement of Naval Architecture and Ocean Engineering, Pusan National Univ.) ;
  • Kim, Jeong-Hyeon (Departement of Naval Architecture and Ocean Engineering, Pusan National Univ.) ;
  • Lee, Chi-Seung (Departement of Naval Architecture and Ocean Engineering, Pusan National Univ.) ;
  • Kim, Myung-Hyun (Departement of Naval Architecture and Ocean Engineering, Pusan National Univ.) ;
  • Lee, Jae-Myung (Departement of Naval Architecture and Ocean Engineering, Pusan National Univ.)
  • 김슬기 (부산대학교 조선해양공학과) ;
  • 김정현 (부산대학교 조선해양공학과) ;
  • 이치승 (부산대학교 조선해양공학과) ;
  • 김명현 (부산대학교 조선해양공학과) ;
  • 이제명 (부산대학교 조선해양공학과)
  • Received : 2014.06.26
  • Accepted : 2014.10.22
  • Published : 2015.02.28
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Abstract

In this paper, computational evaluation method for fatigue crack growth rate(FCGR) based on material viscoplastic-damage model is proposed. Viscoplastic-damage model expressing material constitutive behavior of 7% nickel steel is introduced and is implemented into commercial finite element analysis(FEA) code, ABAQUS, as a user defined material subroutine(UMAT) for application in the FEA environments. Verification of developed UMAT and material parameters of material model are carried out by uniaxial tensile test simulations of 7% nickel steel. Moreover, jump-in-cycles procedure and rearrangement of critical damage are employed and also implemented to the ABAQUS UMAT for fatigue damage analysis. Typical FCGR test results such as relationship between crack length and number of cycles and relationship between da/dN and ${\Delta}K$ could be obtained from FCGR test simulation using developed UMAT and these results are compared with experimental results in order to verify of proposed computational method.

본 논문에서는 재료 점소성-손상모델을 기반으로 한 피로균열 진전속도(FCGR) 전산 평가법을 제안한다. 7% 니켈강 재료 거동을 모사하는 점소성-손상모델을 소개하고, 이의 유한요소해석 플랫폼에의 적용을 위해 상용 유한요소해석 프로그램인 ABAQUS에서 제공하는 사용자 정의 재료 서브루틴(UMAT)에 재료모델을 탑재하였다. 개발 UMAT의 검증을 위해 7% 니켈강 재료 인장시험 시뮬레이션을 수행하였으며, 이를 통해 재료정수를 획득하였다. 또한, 피로하중에 따른 손상해석에 있어 계산 시간 단축을 위한 jump-in-cycles 과정과 임계 손상 값 조정 및 피로 예비 균열 시뮬레이션을 수행하였고 이들 과정을 개발 UMAT에 탑재하여 해석을 수행하였다. 개발 UMAT을 활용하여 7% 니켈강의 상온 FCGR 테스트 시뮬레이션을 수행하였으며, 균열길이(a)와 주기 수(number of cycles)의 관계 및 1 cycle 당 균열성장량(da/dN)과 응력확대계수 진폭(${\Delta}K$)의 관계 등의 결과를 실험결과와 비교하여 검증하였다.

Keywords

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