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증기발생기 세관 와전류 탐상신호의 모델링기반 해석 및 실험적 검증
송성진,김영환,김의래,임창재,이진호 한국비파괴검사학회 2004 한국비파괴검사학회지 Vol.24 No.1
증기 발생기 세관의 결함을 정량적으로 평가하기 위해서 신경회로망과 전자기 유한요소 모델링을 사용한 모델링기반 와전류 신호해석기법을 개발해왔다. 본 연구에서는 개발된 신호해석 기법을 검증하기 위해서 실제로 얻어진 와전류 신호를 해석하였다. 유한요소 모델링을 이용하여 생성된 모사 와전류 신호로 데이터베이스를 구성하였으며, 이들을 사용하여 PPN 분류기와 BPNN 크기 산정 신경회로망을 학습시켰다. 축대칭 가공 결함에서 실험 와전류 신호를 획득하였으며, 이 신호를 신경회로망에 입력시켜서 신호를 해석하였다. 신호 해석 결과는 매우 우수하여, 모델링을 이용하여 개발한 신호해석기법은 실제 와전류 신호 해석에 활용할 수 있음을 알았다. Model-based inversion tools for eddy current signals have been developed by combining neural networks and finite element modeling, for quantitative flaw characterization in steam generator tubes. In the present work, interpretation of experimental eddy current signals was carried out in order to validate the developed inversion tools. A database was constructed using the synthetic flaw signals generated by the finite element model. The hybrid neural networks composed of a PNN classifier and BPNN size estimators were trained using the synthetic signals. Experimental eddy current signals were obtained from axisymmetric artificial flaws. Interpretation of flaw signals was conducted by feeding the experimental signals into the neural networks. The interpretation was excellent, which shows that the developed inversion tools would be applicable to the interpretation of real eddy current signals.
3 차원 모델을 이용한 주조과정에서의 용탕의 충전 및 응고과정에 관한 수치적 연구
조인성,목진호,이진호 대한금속재료학회(대한금속학회) 2000 대한금속·재료학회지 Vol.38 No.9
A numerical algorithm which simulates a three-dimensional casting process in a rectangular mold was developed and tested. To analyze filling process, the VOF method is used with the SIMPLER algorithm and, to analyze solidification process, the Equivalent Specific Heat method is used also with the SIMPLER algorithm. Though the complete symmetric plane assumption in z-direction was adopted in a two-dimensional analysis, it was shown that flow patterns during filling, a point of time when the residual flow decayed and the intensity of natural convection differed in each plane in a three-dimensional analysis due to z-directional velocity components and boundary conditions. In addition, the heat transfer analysis in a mold were also done and results showed that the mold temperature varied in considerably wide range which was different from the convectional analysis of constant heat sink temperature assumption.