원주방향 유도초음파 기반 대구경 용수배관 결함 탐지를 위한 관외면 전자기 음향 트랜스듀서 개발

박민수(Min Soo Park),마평식(Pyung Sik Ma),하종문(Jong Moon Ha),이중석(Joong Seok Lee),승홍민(Hong Min Seung) 한국비파괴검사학회 2020 한국비파괴검사학회지 Vol.40 No.3

본 연구에서는 대구경 용수배관 검사를 위해 배관 외면의 특정 지점에 설치하여 내부 결함의 위치를 효과적으로 파악할 수 있는 관외면 유도초음파 트랜스듀서를 개발하였다. 개발된 트랜스듀서는 배관의 원주방향을 따라 전파하는 최저차의 전단파 모드만을 발생 및 측정할 수 있게 설계되었다. 특히 배관 외면에 설치된 후 축방향을 따라 이동하며 보다 넓은 영역을 탐상하기 위해 전자기 음향 트랜스듀서 기술을 이용하여 비접촉식으로 개발되었으며 축 방향 이동을 고려하여 트랜스듀서 외관을 고안하였다. 특정 주파수에 맞추어 전단파 측정 신호크기를 향상시키기 위하여 수치해석을 이용해 원주방향 전단파의 분산 특성을 우선 파악한 후 이를 반영하여 트랜스듀서를 설계하였고 실제 용수배관 시편에 설치하여 원주방향 전단파를 측정하고 주파수 특성을 검증하였다. 아울러 트랜스듀서의 성능을 파악하는 실험들을 추가적으로 수행하였으며 여러 형상의 인공 결함들에 대해 결함 신호를 성공적으로 취득하였다. 특정 결함에 대해 축 방향으로 센서를 이동시키며 취득한 신호로 국부 영역에 대해 검사 영상을 얻음으로써 대구경 용수배관의 결함 탐지 가능성을 확보하였다. 추후 자동화된 시스템 형태로 구축 및 발전시켜 실제 외부에 설치된 대구경 용수배관에 적용하고자 한다. In this research, we developed a guided wave transducer system that can be installed on the outside of a large water supply pipe to detect defects. The transducer generates and measures the fundamental shear-horizontal wave mode (SH0 mode) propagating along the circumferential direction of the pipe. In particular, by moving the transducers along the axial direction, it can cover a relatively large area of the pipe efficiently. To this end, the transducer was designed to be a noncontact type using electromagnetic acoustic transducer (EMAT) technology. To enhance the transducer output at a target frequency, the dispersion characteristic of the circumferential SH waves was analyzed by numerical simulations, and the results were considered for the EMAT design process. The frequency characteristic was confirmed by experiments with a water supply pipe specimen. Afterward, we carried out several experiments to examine the EMAT performance, and successfully obtained the defect signals reflected from artificially machined defects. In addition, we obtained the inspection image of the target defect by moving the EMAT along the axial direction manually. In so doing, feasible defect detection in water supply pipes was achieved by the proposed method. In the future, further research on actual applications will be conducted.

4방향흔들림방지버팀대의 구조 안정성 및 내진 성능 연구

오수언,좌성훈,이항준 한국재난정보학회 2022 한국재난정보학회 논문집 Vol.18 No.3

Purpose: In this study, we developed a 4-way sway prevention brace that efficiently reduces the installation area and has excellent stability and seismic performance compared to the conventionl sway prevention brace used in existing firefighting facilities. The performance and reliability of the developed 4-way way prevention brace were analyzed by the tensile, compression tests and seismic tests. Method: As the static test, 4-way sway prevention braces were installed on the horizontal and vertical pipes to perform the tensile and compression tests based on the KFI certification standard and the maximum movement was measured at the rated load. As a dynamic test, 4-way sway prevention braces were installed in the pipes filled with water, and the test response spectrum to the input excitation wave were measured through the acceleration sensors. After the seismic tests, separation, failure, and local deformation of the pipes, and 4-way sway prevention braces were not observed. Result: The results of the tensile and compression tests indicated that the maximum movement of the pipe during tension and compression was 50% to 70% or less compared to the certification values, indicating that the performances of the 4-way sway prevention braces were very excellent. The results of the the seismic tests indicated that the test response spectrum of the 4-way sway prevention braces is within the required response spectrum. Conclusion: In this study, it was found that the 4-way sway prevention braces satisfied the KFI certification standard and were superior compared to the existing sway prevention brace in terms of the stability, cost, and installation area. 연구목적: 본 연구에서는 기존 소방 시설에 사용되고 있는 흔들림방지버팀대에 비하여 설치 면적을 효율적으로 감소시키고, 안정성과 내진 성능이 우수한 4방향 흔들림방지버팀대를 개발하였다. 개발된 4방향 흔들림방지버팀대의 성능 및 신뢰성을 인장 및 압축 시험과 내진 시험을 통하여 검증하였다. 연구방법: KFI 인증 기준에 따라 정적시험으로서 수평 및 수직 배관에 4방향 흔들림방지버팀태을 설치하여 인장 및 압축 시험을 수행하였으며, 정격 하중에 최대 움직임을 측정하였다. 또한 동적시험으로서 물이 채워진 배관에 4방향 흔들림방지버팀태를 설치하고 가속도센서를 통하여 입력 가진파에 대한 시험응답스펙트럼을 측정하였다. 또한 내진 시험 후 배관 및 흔들림방지버팀대의 이탈, 파손 및 국부변형을 관찰하였다. 연구결과: 인장 및 압축 실험을 수행한 결과, 인장 및 압축 시에 배관의 최대 움직임은 규정 기준 대비 50% ~ 70% 이하로서 4방향 흔들림방지버팀태의 성능이 매우 우수함을 알 수 있었다. 4방향 흔들림방지버팀태의 내진 시험결과 ,시험응답스펙트럼이 요구응답스펙트럼을 포괄하고 있음을 알 수 있었다. 시험 종료 후에 배관 및 흔들림방지버팀대의 이탈이나 파손 및 국부변형 등은 발생하지 않았으며, 시설물의 구조적 안정성이 유지됨을 확인할 수 있었다. 결론: 본 연구에서는 정적 실험 및 동적 실험을 통하여, 개발된 4방향 흔들림방지버팀대가 KFI 인중 기준을 만족하고 있음을 알 수 있었고, 기존 흔들림방지버팀대에 비하여 효율성과 경제성 및 안정성과 내진 성능이 우수함을 확인할 수 있었다.

유한요소법을 이용한 축방향 결함 배관의 소성붕괴 해석

전현규 한국기계기술학회 2000 한국기계기술학회지 Vol.2 No.1

비 이상화된 원주방향 관통균열이 존재하는 두꺼운 배관의 균열 성장 매개변수 계산

한태송(Tae-Song Han),허남수(Nam-Su Huh),박치용(Chi-Yong Park) 한국비파괴검사학회 2013 한국비파괴검사학회지 Vol.33 No.2

본 논문에서는 두꺼운 배관에 존재하는 비 이상화된 원주방향 관통균열의 탄성 응력확대계수 해를 제시하였다. 이를 위해 3차원 탄성 유한요소해석을 수행하였으며, 배관의 형상 및 비 이상화된 원주방향 관통균열의 영향을 고려하기 위해 배관의 두께, 기준균열길이 및 관통균열길이 비를 체계적으로 변화시켰다. 하중 조건으로는 인장하중, 굽힘모멘트 및 내압을 고려하였다. 또한 본 논문에서는 이상화된 원주방향 관통 균열로부터 비 이상화된 원주방향 관통균열의 응력확대계수를 쉽게 계산하기 위해 관통균열 보정계수를 제시하였다. 본 논문의 결과는 실제 균열성장거동을 고려하여 원자력 배관의 배관파단확률을 보다 정확하게 계산하기 위해 적용될 수 있다. The present paper provides the elastic stress intensity factors(SIFs) of thick-walled cylinder with non-idealized circumferential through-wall cracks. For estimating these elastic SIFs, the systematic three-dimensional(3D) elastic finite element(FE) analyses were performed. In order to consider practical shape of thick-walled cylinder and non-idealized circumferential through-wall crack, the values of thickness of cylinder, reference crack length and crack length ratio were systematically varied. As for loading conditions, axial tension, global bending and internal pressure were considered. In particular, in order to calculate the SIFs of thick-walled cylinder with non-idealized circumferential through-wall crack from those of thick-walled cylinder with idealized circumferential through-wall crack, the correction factor representing the effect of non-idealized crack on the SIFs were proposed in this paper. The present results can be applied to accurately evaluate the rupture probabilities of nuclear piping considering actual crack growth behaviors.

비 이상화된 원주방향 관통균열이 존재하는 두꺼운 배관의 균열 성장 매개변수 계산

한태송,허남수,박치용,Han, Tae-Song,Huh, Nam-Su,Park, Chi-Yong 한국비파괴검사학회 2013 한국비파괴검사학회지 Vol.32 No.5

본 논문에서는 두꺼운 배관에 존재하는 비 이상화된 원주방향 관통균열의 탄성 응력확대계수 해를 제시하였다. 이를 위해 3차원 탄성 유한요소해석을 수행하였으며, 배관의 형상 및 비 이상화된 원주방향 관통균열의 영향을 고려하기 위해 배관의 두께, 기준균열길이 및 관통균열길이 비를 체계적으로 변화시켰다. 하중 조건으로는 인장하중, 굽힘모멘트 및 내압을 고려하였다. 또한 본 논문에서는 이상화된 원주방향 관통 균열로부터 비 이상화된 원주방향 관통균열의 응력확대계수를 쉽게 계산하기 위해 관통균열 보정계수를 제시하였다. 본 논문의 결과는 실제 균열성장거동을 고려하여 원자력 배관의 배관파단확률을 보다 정확하게 계산하기 위해 적용될 수 있다. The present paper provides the elastic stress intensity factors(SIFs) of thick-walled cylinder with non-idealized circumferential through-wall cracks. For estimating these elastic SIFs, the systematic three-dimensional(3D) elastic finite element(FE) analyses were performed. In order to consider practical shape of thick-walled cylinder and non-idealized circumferential through-wall crack, the values of thickness of cylinder, reference crack length and crack length ratio were systematically varied. As for loading conditions, axial tension, global bending and internal pressure were considered. In particular, in order to calculate the SIFs of thick-walled cylinder with non-idealized circumferential through-wall crack from those of thick-walled cylinder with idealized circumferential through-wall crack, the correction factor representing the effect of non-idealized crack on the SIFs were proposed in this paper. The present results can be applied to accurately evaluate the rupture probabilities of nuclear piping considering actual crack growth behaviors.

두꺼운 배관에 존재하는 축방향 경사관통균열의 탄성파괴역학 매개변수 계산

한태송(Tae-Song Han),허남수(Nam-Su Huh) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.12

본 논문에서는 두꺼운 배관에 존재하는 축방향 경사관통균열의 탄성응력확대계수 및 탄성 균열열림변위 해를 제시하였다. 이를 위해 배관의 두께, 기준균열길이, 경사관통균열 길이비를 체계적으로 변화시키며 3차원 탄성 유한요소해석을 수행하였다. 하중조건으로는 균열 성장에 영향을 미치는 내압을 고려 하였다. 유한요소해석 결과를 바탕으로 두꺼운 배관에 존재하는 이상적인 축방향 관통균열과 경사관통균열에 대한 탄성응력확대계수와 탄성 균열열림변위를 균열선단 및 두께를 따라 제시하였다. 특히 응력확대 계수의 경우에는 이상적인 축방향 관통균열 결과로부터 쉽게 경사관통균열의 응력확대계수를 구할 수 있는 경사관통균열 보정계수를 제시하였다. The present paper provides the elastic stress intensity factors (SIFs) and the crack opening displacements (CODs) of a thick-walled pipe with a slanted axial through-wall crack. For estimating these elastic fracture mechanics parameters, systematic three-dimensional elastic finite element (FE) analyses were performed by considering geometric variables, i.e., thickness of pipe, reference crack length, and crack length ratio, affecting the SIFs and CODs. As for loading condition, the internal pressure was considered. Based on the FE results, the SIFs and CODs of slanted axial through-wall cracks in a thickwalled pipe along the crack front and the wall thickness were calculated. In particular, to calculate the SIFs of a thick-walled pipe with a slanted axial through-wall crack from those of a thick-walled pipe with an idealized axial through-wall crack, a slant correction factor representing the effect of the slant crack on the SIFs was proposed.

원주방향 관통균열이 존재하는 고인성 얇은 배관의 소성영향함수 계산

전다솜(Da-Som Jeon),이용민(Yong-Min Lee),장윤석(Yoon-Suk Chang),허남수(Nam-Su Huh),이상민(Sang-Min Lee),김용범(Yong-Beom Kim) 대한기계학회 2017 대한기계학회 춘추학술대회 Vol.2017 No.11

For Leak-Before-Break (LBB) assessment in nuclear piping system, it is required to accurately predict Elastic-Plastic Fracture Mechanics (EPFM) parameters. One of well-known method to predict EPFM parameter is GE/EPRI method using plastic influence function for fully plastic terms of EPFM parameter. However, the current plastic influence functions of GE/EPRI method are proposed only for limited pipe/crack geometries and strain hardening exponents. Thus, in the present study, the extension of plastic influence functions is pursued to thin-walled pipe with high strain hardening exponents for possible application to high toughness pipe using 3-D FE analyses.

원주방향 경사관통균열이 존재하는 두꺼운 배관의 탄성 균열열림변위

한태송,허남수,심도준,김진수,이진호,Han, Tae-Song,Huh, Nam-Su,Shim, Do-Jun,Kim, Jin-Su,Lee, Jin-Ho 한국압력기기공학회 2012 한국압력기기공학회 논문집 Vol.8 No.3

According to recent research on leak-rate estimates to assess rupture probabilities of nuclear piping which contains a circumferential surface/through-wall cracks due to PWSCC, i.e., xLPR (Extremely Low Probability of Rupture) program, it has been revealed that the use of crack shape with an idealized circumferential through-wall crack during actual crack growth can lead to overestimate of the leak-rate. Thus, for accurate estimation of the leak-rate during crack growth, the more realistic crack shape that can simulate the crack shape transition from surface crack to through-wall crack should be used. In this context, in the present study, the elastic crack opening displacement of slanted circumferential through-wall crack in thick-walled cylinder was proposed based on 3-dimensional elastic finite element fracture mechanics analyses. To propose the elastic crack opening displacement of slanted circumferential through-wall crack in thick-walled cylinder, the geometric variables affecting crack opening displacement, i.e., thickness of cylinder, reference inner crack length and slant crack ratio were systematically varied. In terms of loading conditions, axial tension, global bending moment and internal pressure were considered. The present results can be applied to calculate the leak-rate considering more realistic crack shape transition from surface crack to idealized through-wall crack, and can be expected to enhance current leak-rate estimation scheme, for instance, in xLPR program etc.

원주방향균열이 존재하는 원전 배관계통의 파괴거동에 관한 실험적 연구(I) - 직관부에서의 균열거동 평가 -

최영환,박윤원,Choi, Young-Hwan,Park, Youn-Won,Wilkowski, Gery 대한기계학회 1999 大韓機械學會論文集A Vol.23 No.7

The purpose of this study is to investigate experimentally the effects of both seismic loading and crack length on the fracture behavior of piping system with a circumferential crack in nuclear power plants. The experiments were performed using both large scale piping system facility and 4 points bending test machine under PWR operating conditions. The difference in the load carrying capacities between cracked piping and non-cracked piping was also investigated using the results from experiments and numerical calculations. The results obtained from the experiments and estimation are as follows : (1) The safety margin under seismic loading is larger than those under quasi static loading or simple cyclic loading. (2) There was no significant effect of crack length on tincture behavior of piping system with both a surface crack and a through-wall crack. (3) The load carrying capacity in cracked piping was reduced by factors of 7 to 46 compared to non-cracked piping.

배관에 존재하는 원주방향 표면균열에 대한 파괴거동 해석 (I) -J-적분 예측식 -

김진수,김윤재,김영진,Kim, Jin-Su,Kim, Yun-Jae,Kim, Yeong-Jin 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.1

This paper provides the fully plastic J solutions for circumferential cracked pipes with inner, semi- elliptical surface cracks, subject to internal pressure and global bending. Solutions are given in the form of two different approaches, the GEF/EPRl approach and the reference stress approach. For the GE/EPRl approach, the plastic influence functions for fully plastic J are tabulated based on extensive 3-D FE calculations using the Ramberg-Osgood (R-O) materials, covering a wide range of pipe and crack geometries. The developed GEf/EPRl-type fully plastic J estimation equations are then re-formulated using the concept of the reference stress approach for wider applications. Based on the FE results, optimized reference load solutions for the definition of the reference stress are found for internal pressure and for global bending. Advantages of the reference stress based approach over the GE/EPRl-type approach are fully discussed. Validation of the proposed reference stress based J estimation equations will be given in Part II, based on 3-D elastic-plastic or elastic creep FE results using typical tensile properties of stainless steels and generalized creep- deformation behaviours.