Journal of the Korean Society for Nondestructive Testing (비파괴검사학회지)

The Korean Society for Nondestructive Testing (한국비파괴검사학회)
권호 표지

Fabrication of Mechanical fatigue flawed Specimen and Evaluation of Flaw Size

기계적 피로결함 시험편 제조 및 결함 크기 평가

  • Hong, Jae-Keun (Authorized Nuclear Inspection Group, Korea Institute of Machinery & Materials) ;
  • Kim, Woo-Sung (Authorized Nuclear Inspection Group, Korea Institute of Machinery & Materials) ;
  • Son, Young-Ho (Authorized Nuclear Inspection Group, Korea Institute of Machinery & Materials) ;
  • Park, Ban-Uk (Authorized Nuclear Inspection Group, Korea Institute of Machinery & Materials)
  • Published : 2003.02.28
Download PDF
⟨ Previous Next ⟩

Abstract

Performance demonstration with real flawed specimens has been strongly required for nondestructive evaluation of safety class components in nuclear power plant. Mechanical or thermal fatigue crack and intergranular stress corrosion cracking could be occured in the in-service nuclear power plant and mechanical fatigue crack was selected to study in this paper. Specimen was designed to produce mechanical fatigue flaw under tensile stress. The number of cycles and the level of stress were controlled to obtain the desired flaw roughness. After the accurate physical measurement of the flaw size and location, fracture surface was seal-welded in place to ensure the designed location and site. The remaining weld groove was then filled by using gas-tungsten are welding(GTAW) and flux-cored arc welding(FCAW). Results of radio graphic and ultrasonic testing showed that fatigue cracks were consistent with the designed size and location in the final specimens.

원자력발전소의 안전성등급 기기에 적용되는 비파괴검사는 실제 결함을 실현한 시험편을 사용하여 결함탐지능력을 검증하도록 하는 기량검증이 요구되고 있다. 가동중인 원전에서 발생 가능한 균열으로는 기계적 피로균열, 열 피로균열 및 입계부식균열 등이 있으나 본 연구에서는 기계적 피로균열을 대상으로 하였다. 인장 피로하중을 사용하여 기계적 피로결함을 제조하기 위해서 시험편을 설계하였고 원하는 피로결함 파면의 조도를 얻기 위해서 인가하중의 크기 및 사이클 수를 조절하여 피로결함을 발생시켰다. 발생된 결함에 대한 정확한 크기와 위치에 대한 물리적 정보를 얻은 후에 결함이 설계된 크기와 위치에 존재하도록 기밀용접을 실시하였다. 기밀용접 후 잔여 용접 흠은 가스 텅스텐 아크용접 및 플럭스 코어드 아크용접으로 채워졌다. 최종 완성된 피로결함 시험편을 방사선투과검사 및 초음파탐상검사를 통하여 검사한 결과, 설계된 길이와 깊이로 피로결함이 형성되었음을 확인하였다.

Keywords

References

  1. ASME Boiler and Pressure Vessel Code, Section XI, Rules for Inservice Inspection of Nuclear Power Plant Components, The American Society of Mechanical Engineers (1995)
  2. R. L. Edwards, P. D. Watson and G. J. Gruber, 'Fabrication of Specimens With Controlled Flaws for Procedure Development and Personnel Training and Qualification,' 12th International Conference on NDE in the Nuclear and Pressure Vessel Industries, pp. 93-100 (1994)
  3. R. Edwards, G. Gruber and P. Watson,'Fabrication of Performance Demonstration Initiative Specimens with Controlled Flaws', 13th International Conference on NDE in the Nuclear and Pressure Vessel Industries, pp. 167-176, (1995)
  4. 장기상, '한국형기량검증 System 준비현황‘, 원전 lSI Workshop 발표논문집, pp. 2-16 (2002)
  5. A. L. Pherigo and G. L. Pherigo, 'Flaw Implant Techniques Used to Manufacture Specimens for ASME Section XI, Appendix VII-VIII,' The 1993 Pressure Vessels and Piping Conference, vol. 57, pp. 87-91 (1993)
  6. G. L. Pherigo and A. L. Pherigo, 'Implanting Flaws for NDT Validation,' 4th Structural Materials Technology IV: an NDT Conference, pp. 323-328, Mar. (2000)
  7. G. L. Pherigo, A. L. Pherigo, 'Using Flaw Implants to Qualify Nuclear NDE Personnel,' 12th International Conference on NDE in the Nuclear and Pressure Vessel Industries, pp. 81-84 (1994)
  8. G. L. Pherigo, 'Flawed Specimen Design and Manufacture for ASME Section XI, Appendix VII-VIII,' 11th International Conference on NDE in the Nuclear and Pressure Vessel Industries, pp. 225-230 (1992)
  9. G .L. Pherigo, 'Performance Demonstration Testing at the EPRI NDE Center for Intergranular Stress Corrosion Cracking in BWR Piping,' NDE in the Nuclear Industry, pp. 45-48 (1987)
  10. P. Watson, R. L. Edward, 'Fabrication of Test Specimens Simulating IGSCC for Demonstra- tion and Inspection Technology Evaluation,' 14th International Conference on NDE in the Nuclear and Pressure Vessel Industries, pp. 165-168 (1997)