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원주 방향 두께가 불균일한 배관의 진동 모드 특성을 이용한 배관 감육 검사 기법 연구

Pipe Wall-Thinning Inspection using Vibration Modes of Pipes with Circumferentially Varying Thickness

  • 한순우 (한국원자력연구원 원자력융합기술개발부) ;
  • 서정석 (한국원자력연구원 원자력융합기술개발부) ;
  • 박진호 (한국원자력연구원 원자력융합기술개발부)
  • Han, Soon-Woo (Dept. of Nuclear Convergence Technology, Korea Atomic Energy Research Institute) ;
  • Seo, Jeong-Seok (Dept. of Nuclear Convergence Technology, Korea Atomic Energy Research Institute) ;
  • Park, Jin-Ho (Dept. of Nuclear Convergence Technology, Korea Atomic Energy Research Institute)
  • 투고 : 2016.07.27
  • 심사 : 2017.01.11
  • 발행 : 2017.02.28

초록

현재의 초음파 두께 측정에 기반한 배관 감육 검사 속도를 개선하기 위해 배관 쉘 진동 모드의 고유 진동수 변화를 이용한 감육 검사 기법을 제안하였다. 감육이 발생한 부위의 축방향 수직 단면의 두께는 원주 방향을 따라 불균일하게 변화하는데, 두께가 균일한 경우에 비해 쉘 모드의 고유 진동수가 감소하거나 두 개 이상으로 분기됨을 확인하였다. 배관의 고유 진동수는 한 번의 측정으로도 평가할 수 있으므로, 제안한 방법을 이용하면 축방향 수직 단면의 평균 두께 변화를 빠르게 확인할 수 있어 초음파 두께 측정 방식에 비해 신속한 감육 검사가 가능하다. 본 논문에서는 제안 기법의 원리를 설명하고, 2차원과 3차원 감육 배관 모델 및 시편을 이용한 전산 해석과 실험을 통해 제안한 기법의 적용성을 검증하였다.

This work proposes an alternative pipe wall-thinning inspection method based on change of eigenfrequencies of shell vibration modes in wall-thinned pipes. It takes much time to detect wall-thinning of pipes using ultrasonic thickness gauge and only a limited number of pipes are under regular inspection. In a pipe with locally decreased thickness, stiffness varies along circumferential direction and natural frequencies of shell vibration modes of the pipe change or frequencies of same modes bifurcate into two different values. Therefore, one can monitor pipe wall-thinning by measuring change of natural frequencies or estimate wall-thinning shape qualitatively. The feasibility of the proposed method was studied by FE vibration analysis for wall-thinned pipes. Modal testing was also carried out for the pipes with artificial wall-thinned section to verify the working performance of the suggested technique.

키워드

참고문헌

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