• 한국자기학회지
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• 제23권1호
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• pp.18-25
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• 2013

배관용 비파괴 검사에서 자기누설방식을 이용하여 배관의 결함을 검출하도록 개발된 탐상 시스템 장비를 MFL PIG(Magnetic Flux Leakage Pipeline Inspection Gauge)라 한다. 이 장비는 투자율이 큰 금속 배관의 길이 방향인 축방향으로 자기장을 형성하고, 결함이 있는 부분에 발생하는 누설 자속 신호를 홀센서를 이용하여 검출한다. 하지만 MFL PIG는 배관에 축방향으로 발생한 미소결함에 대해서는 누설 자속의 발생량이 미세하여 결함 유무를 판별하기 어렵다. 본 논문에서는 배관에 발생한 축방향 미소결함을 검출하기위해 CMFL(Circumferential MFL) PIG를 적용하였고, 결함 주위에 발생한 누설 자속 신호의 크기 및 분포를 3차원 정자계 유한요소법을 이용하여 검출 및 분석하였다. 이러한 검출 신호로부터 길이, 폭, 깊이와 같은 결함의 형상을 판정하는 기법을 제안하였고 이를 CMFL PIG 모의 성능 실험을 통하여 비교 및 검증하였다.

• 대한기관식도과학회:학술대회논문집
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• 대한기관식도과학회 1983년도 제17차 학술대회연제순서 및 초록
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• pp.14.3-14
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• 1983

최근 급속히 증가 추세에 있는 각종 산업재해와 교통사고로 인한 심한 신체적 손상, 심혈관계수술 및 호흡계수술등을 받은 환자에서 기도유지를 위해 사용되는 기관내삽관과 기관절개위의 후유증 또는 두부외상으로 발생하는 외상성 기관협착의 빈도가 점차 높아짐에 따라서 이에 대한 치료로 기관성형술이 주목할만한 관심을 보여주고 있다. 기관성형술의 방법으로는 손상된 기관의 위치나 크기에 따라 여러 가지가 있으나 부분절제 및 단단문합술, 경부피변과 자가이식물질등을 이용한 재건술을 들 수 있다. 1965년 Grillo가 개에서 환상절제후 기관성형술을 시행한 이래 환상기관협착의 경우에는 부분절제및 단단문합술이 많이 이용되고 있다. 또한 자가이식물질로는 비중격, 늑골, 이개의 연골이 많이 사용되고 있으며, Consiglio와 Caputo가 이개연골을 이용하여 기관성형술을 시행한 이래 Morgenstein은 기관결손이 있는 환자에서 이개연골을 사용하여 혼합이식을 시행하여 성공적인 재건을 보고하였다. 이개연골이식은 이비인후과의사에게는 쉽게 채취하여 활용할 수 있고 친근감이 있는 장점이 있다. 최근 본교실에서는 5예의 기관협착증 환자에서 이개연골이식(2예), 부분절제후 단단문합술(3예)에 의한 기관성형술을 시행하여 좋은 결과를 얻었기에 문헌고찰과 함께 보고하는 바이다.

• 대한기계학회논문집A
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• 제37권4호
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• pp.521-527
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• 2013

본 논문에서는 3 차원 유한요소해석을 통해 표면균열이 있는 직관에 내압, 굽힘, 그리고 비틀림의 단일 또는 복합하중이 작용하는 경우의 응력확대계수를 연구하였다. 두 가지 결함평가코드(API-579-1, RCC-MR A16)를 각각 유한요소해석 결과와 비교하여 코드 간의 차이 및 해석의 신뢰성을 확인하였다. 응력확대계수는 적분 경로에 독립적이기 때문에 민감하지 않다고 알려져 있는데 3 차원 유한요소해석을 통해 요소 수에 대한 민감도를 확인하였다. 또한 균열형상의 정의방법에 따른 유한요소해석 결과의 차이와 두 가지 결함평가코드를 사용한 결과의 차이를 확인하였다.

• 비파괴검사학회지
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• 제20권6호
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• pp.555-561
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• 2000

다양한 기계가공 결함을 유기한 공칭 외경 100mm의 덕타일 주철관을 대상으로 원거리장 와전류 검사를 수행하였다. 상수도 배수관으로 사용되는 주철관은 제조 단계의 큰 허용 오차 때문에 두께가 일정하지 않고 단면이 비대칭적인 특징을 지니므로, 원거리장 와전류 탐상 신호에는 배관 축방향에 걸친 장범위 잡음이 존재하게 된다. 본 논문에서는 장범위에 걸친 배경잡음을 효과적으로 제거하기 위하여 이동구간 평균법을 응용하였고, 결함의 깊이와 원주방향 정도를 정량적으로 평가하기 위하여 voltage plane 극좌표 (VPPP) 방법을 활용하였다. 이동구간 평균처리로서 신호비를 일차적으로 향상시킨 다음 VPPP 기법을 이용하여 결함신호를 얻은 결과, 결함신호가 VPPP상의 기준점에서 x 축과 이루는 각이 결함 깊이와 직선적인 상관 관계가 있음을 확인하였다. 따라서 배관과 동축으로 놓인 탐촉코일을 이용한 원거리장 와전류 검사로서 매설 상수도 배관 내 외부에 존재하는 부식결함을 비파괴 정량평가할 수 있는 기반을 구축하였다.

• 대한치과의사협회지
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• 제56권12호
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• pp.667-685
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• 2018

Objectives: Aim of this study was to evaluate bone regenerative efficacy of a chemically cross-linked porcine collagen membrane (CM) when used in combination with highly soluble biphasic calcium phosphate (BCP). Materials and methods: Physiochemical properties of the experimental collagen membrane were analyzed. Four circumferential defects with diameter of 8 mm were created in each calvarium of New Zealand white rabbits (n = 10). Defects were randomly allocated to one of following 4 groups: 1) BCP-CM (BCP (20% hydroxyapatite/80% ${\beta}$-tricalcium phosphate) covered with the prepared collagen membrane), 2) BCP (only BCP used), 3) CM (only the prepared collagen membrane used), and 4) C (control; only blood clot). After 2 weeks (n = 5) and 8 weeks (n = 5), histologic and histomorphometric analyses were performed. Results: The experimental collagen membrane exhibited dense and compact structure, relatively high tensile strength and lower degradability. Histologic analyses revealed that new bone increased rapidly at 2 weeks, while defect was preserved at 8 weeks. Histomorphometric analyses revealed that the new bone areas increased in the BCP-grafted groups over 8 weeks, with BCP-CM exhibiting greater total augmented area than that of BCP group both at 2 weeks ($27.12{\pm}3.99$ versus $21.97{\pm}2.27mm^2$) and 8 weeks ($25.75{\pm}1.82$ versus $22.48{\pm}1.10mm^2$) (P < 0.05). Conclusions: The experimental collagen membrane successfully preserved localized defect for 8 weeks despite early rapid resorption of BCP. Within the study limitations, combined use of the chemically cross-linked porcine collagen membrane and highly soluble BCP aided localized bone regeneration.

• Journal of Periodontal and Implant Science
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• 제46권5호
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• pp.303-319
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• 2016

Purpose: The purpose of this animal study was to perform a 3-dimensional micro-computed tomography (micro-CT) analysis in order to investigate the influence of root surface distance to the alveolar bone and the periodontal ligament on periodontal wound healing after a guided tissue regeneration (GTR) procedure. Methods: Three adult Sus scrofa domesticus specimens were used. The study sample included 6 teeth, corresponding to 2 third mandibular incisors from each animal. After coronectomy, a circumferential bone defect was created in each tooth by means of calibrated piezoelectric inserts. The experimental defects had depths of 3 mm, 5 mm, 7 mm, 9 mm, and 11 mm, with a constant width of 2 mm. One tooth with no defect was used as a control. The defects were covered with a bioresorbable membrane and protected with a flap. After 6 months, the animals were euthanised and tissue blocks were harvested and preserved for micro-CT analysis. Results: New alveolar bone was consistently present in all experimental defects. Signs of root resorption were observed in all samples, with the extent of resorption directly correlated to the vertical extent of the defect; the medial third of the root was the most commonly affected area. Signs of ankylosis were recorded in the defects that were 3 mm and 7 mm in depth. Density and other indicators of bone quality decreased with increasing defect depth. Conclusions: After a GTR procedure, the periodontal ligament and the alveolar bone appeared to compete in periodontal wound healing. Moreover, the observed decrease in bone quality indicators suggests that intrabony defects beyond a critical size cannot be regenerated. This finding may be relevant for the clinical application of periodontal regeneration, since it implies that GTR has a dimensional limit.

• 한국압력기기공학회 논문집
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• 제6권1호
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• pp.16-22
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• 2010

Cast austenitic stainless steel(CASS) is used in the primary cooling piping system of nuclear power plant for it's relative low cost, corrosion resistance and easy of welding. However, the coarse-grain structure of cast austenitic stainless steel can strongly affect the inspectability of ultrasonic testing. The major problems encountered during inspection are beam skewing, high attenuation and high background noise of CASS component. So far, the best inspection performance involving CASS components have been achieved using low frequency TRL(Transmitter/Receiver side-by-side L wave) angle beam probe. But TRL technique could not detect shallow defect and it contains an uncertainty for sizing capability. Currently, most of researchers are studying to overcome these challenge issue. In this study, low-frequency phased array TRL technique used to detect and sizing the flaws in CF8A cast austenitic stainless steel.As conclusion, we could detect and size not only axial flaw but also circumferential flaw using low frequency phased array technique.

• 대한기계학회논문집A
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• 제27권8호
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• pp.1295-1302
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• 2003

In order to evaluate a failure behavior of pipe with notch-type wall thinning, the present study performed full-scale pipe tests using the 102mm, Schedule 80 pipe specimen simulated notch- and circular-type thinning defects. The pipe tests were conducted under the conditions of both monotonic and cyclic bending moment at a constant internal pressure of 10 MPa. From the results. of experiment the failure mode, load carrying capacity, deformation ability, and fatigue life of a notch-type wall thinned pipe were investigated, and they were compared with those of a circular-type wall thinned pipe. The failure mode of notched pipe was similar to that of circular-type thinned pipe under the monotonic bending load. Under the cyclic bending load, however, the mode was clearly distinguished with variation in the shape of wall thinning. The load carrying capacity of a pipe containing notch-type wall thinning was about the same or slightly lower than that of a pipe containing circular-type wall thinning when the thinning area was subjected to tensile stress, whereas it was higher than that of a pipe containing circular-type thinning defect when the thinning area was subjected to compressive stress. On the other hand, the deformation ability and fatigue life of a notch-type wall thinned pipe was lower than those of a circular-type wall thinned pipe.

• Smart Structures and Systems
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• 제9권5호
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• pp.461-472
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• 2012

This study proposes an optics-based active sensing system for continuous monitoring of underground pipelines in nuclear power plants (NPPs). The proposed system generates and measures guided waves using a single laser source and optical cables. First, a tunable laser is used as a common power source for guided wave generation and sensing. This source laser beam is transmitted through an optical fiber, and the fiber is split into two. One of them is used to actuate macro fiber composite (MFC) transducers for guided wave generation, and the other optical fiber is used with fiber Bragg grating (FBG) sensors to measure guided wave responses. The MFC transducers placed along a circumferential direction of a pipe at one end generate longitudinal and flexural modes, and the corresponding responses are measured using FBG sensors instrumented in the same configuration at the other end. The generated guided waves interact with a defect, and this interaction causes changes in response signals. Then, a damage-sensitive feature is extracted from the response signals using the axi-symmetry nature of the measured pitch-catch signals. The feasibility of the proposed system has been examined through a laboratory experiment.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2001년도 춘계학술대회논문집B
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• pp.235-240
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• 2001

This paper introduces developed prototype intelligent pig which detects corrosion on pipeline by using Magnetic Flux Leakage technology. The 8 inch developed MFL(Magnetic Flux Leakage) pig is composed of 5 yokes which magnetize pipeline wall and 45 Hall sensors which detect MFL signal. The designed MFL modules are analyzed by using magnetic circuit method in order to confirm whether pipeline wall is fully saturated. A variety of artificial defects are manufactured on 8 inch diameter steel pipeline in order to acquire MFL signals. So leakage flux of the axial, radial and circumferential component was acquired as defects. The results of this paper show that design technique for 8 inch MFL pig can be applied to large diameter MFL pig and 0.5mm defect depth can be detected.