초음파 C-scan을 이용한 터빈 블레이드 열차폐코팅의 등온열화에 의한 박리 평가 기법

이호걸(Ho-Girl Lee),김학준(Hak-Joon Kim),송성진(Sung-Jin Song),석창성(Chang-Sung Seok) 한국비파괴검사학회 2016 한국비파괴검사학회지 Vol.36 No.5

가스터빈 블레이드는 고온 고압의 환경 아래 장시간 가동하기 위하여 초합금 모재에 세라믹 코팅으로 이루어진 열차폐코팅(thermal barrier coating, TBC)은 필수요소이다. 하지만 TBC 또한 가스터빈 가동 중 일정 열화온도 및 가동시간에서 top coat의 박리현상이 일어난다. TBC의 박리는 블레이드의 손상과 직결되므로 가스터빈의 안정적인 가동을 위해서 TBC의 박리 평가가 선행되어야 한다. 기존 비파괴평가 기법 연구는 산화알루미늄층(thermally grown oxide, TGO)의 생성 유무 또는 완전 박리의 정성적 평가가 이루어져 왔다. 본 연구에서는 TBC 박리를 정량적으로 평가하기 위해 초음파검사의 C-scan기법을 이용한 TBC의 부분박리손상 map을 구현하였다. 시편들은 1,100˚C로 등온열화하여 각각 열화시간을 변화시킨 시편들을 사용하였다. 단일 탐촉자를 이용한 펄스-에코법으로 C-scan을 수행하였고 TBC 내 부분박리를 검출하기 위해 초음파를 수침법으로 시편에 수직탐상하였다. 그리고 Rogers-Van Buren과 Kim의 이론 반사식을 이용하여 부분박리영역 지름이 1 mm부터 6 mm까지 부분박리지수를 도출했다. 이를 적용하여 각 부분박리지수에 따른 부분박리 손상 map을 영상화하였다. TBC는 열화시간이 증가할수록 부분박리지수에 관계없이 부분박리영역이 모두 증가함을 확인할 수 있었다. 또한 단일 시편 내에서 부분박리지수가 증가할수록 부분박리영역이 감소하는 것을 확인하였다. 부분박리손상 map의 부분박리영역에 따른 분포를 이용하여 TBC의 완전박리 기준과 잔여 수명을 또한 도출할 수 있었다. Thermal barrier coating (TBC) is an essential element consisting of a super-alloy base and ceramic coating designed to achieve long operational time under a high temperature and pressure environment. However, the top coat of TBC can be delaminated at certain temperatures with long operation time. As the delamination of TBC is directly related to the blade damage, the coupling status of the TBC should be assured for reliable operation. Conventional studies of nondestructive evaluation have been made for detecting generation of thermally grown oxide (TGO) or qualitatively evaluating delamination in TBC. In this study, the ultrasonic C-scan method was developed to obtain the damage map inside TBC by estimating the delamination in a quantitative way. All specimens were isothermally degraded at 1,100˚C with different time, having different partial delamination area. To detect partial delamination in TBC, the C-scan was performed by a single transducer using pulse-echo method with normal incidence. Partial delamination coefficients of 1 mm to 6 mm were derived by the proportion of the surface reflection signal and flaw signal which were theoretical signals using Rogers-Van Buren and Kim"s equations. Using the partial delamination coefficients, the partial delamination maps were obtained. Regardless of the partial delamination coefficient, partial delamination area was increased when degradation time was increased in TBC. In addition, a decrease in partial delamination area in each TBC specimen was observed when the partial delamination coefficient was increased. From the portion of the partial delamination maps, the criterion for delamination was derived.

Modified Bristow술식을 이용한 견관절 재발성 전방탈구의 치료

이용걸(Yong Girl Lee),조태환(Tae Hwan Cho),도상수(Sang Su Do),김형주(Hyung Joo Kim),이동균(Dong Kyun Lee),전진호(Jin Ho Chun) 대한정형외과학회 1990 대한정형외과학회지 Vol.25 No.4

연소실 압력 강하에 의한 고체 추진제의 동적 소화

정호걸(Ho-Girl Jung),이창진(Changjin Lee) 한국항공우주학회 2002 韓國航空宇宙學會誌 Vol.30 No.2

전신 및 상체 하네스를 활용한 스노보드 지상훈련자세의 운동역학적 비교 분석

이종훈(Lee, Chong-Hoon),백진호(Back, Jin-Ho),남기정(Nam, Ki-Jeong),엄길호(Eom, Kil-Ho),전윤걸(Jeon, Youn-Girl) 한국체육과학회 2018 한국체육과학회지 Vol.27 No.4

We consider the biomechanical analysis of four professional male snowboarders in order to produce basic data, which allows for improving the snowboarding performances of both athlete and amateur snowboarders. We measured the low limb angle and main muscle activation on snowboarding while the male snowboarder was in a snowboard riding and accoutered with whole body harness or upper body harness in simulator. The results show that the use of the whole body harness is more effective in restricting on hip joint and in activatiing left lateral gastrocnemius when the male snowboarder maintained snowboarding posture on the simulator. Our study suggests that application of whole body harness will be more suitable to posture training on the simulator than using upper body harness.

복사열전달이 고체 추진제의 동적소화에 미치는 영향

정호걸(Ho-Girl Jung),이창진(Changjin Lee) 한국항공우주학회 2003 韓國航空宇宙學會誌 Vol.31 No.2

압력상승이 있는 고체 추진제 비정상 연소에서 복사 열전달 해석

정호걸(Ho-Girl Jung),이창진(Changjin Lee) 한국항공우주학회 2001 韓國航空宇宙學會誌 Vol.29 No.2

노인들의 정적자세 유지를 위한 안정성 비교분석

이종훈(Lee, Chong-Hoon),전윤걸(Jeon, Youn-Girl),엄길호(Eom, Kil-Ho) 한국체육과학회 2019 한국체육과학회지 Vol.28 No.6

We analyzed the trajectories of the center of mass(COM) of elderly people during their quiet upright standing for understanding their balance capabilities, which are closely related to their fall and injury, by using a three-dimensional motion capture system based on inertial measurement units. Healthy elderly men and women participated this study were divided into two groups, which have superior(n=8, M=5, F=3, age=69.75±5.95) and inferior(n=8, M=5, F=3, age=76.62±5.13) balance capabilities, respectively. The criterion of superiority in stability was whether a participant could keep a single limb standing with eyes open during at least ten seconds or not. Coordinate system was set based on x(mediolateral), y(anteroposterior), and z(vertical) axes. It is found that COM distance along the z axis is negatively correlated with COM distance along x and y axes, and velocity along the x and y axes for both groups. More remarkably, for superior group, the minimum value of COM distance along z axis is postively correlated with the minimum value of velocity along x axis. However, for inferior group, the minimum value of COM distance along z axis is positively correlated with COM distance along x and y axes. Our study shows that the characteristics of COM perturbations is useful in understanding the stability capabilities of elderly people. In addition, our study suggests that for improving the stability, the strategic program is needed to stimulate the COM oscillations in x, y, and z axes.

혈관주위세포종의 다발성 척추전이

장종호,임승철,이동걸,노성우 대한신경외과학회 2002 Journal of Korean neurosurgical society Vol.32 No.4

일본 집쥐에서의 서울 바이러스 분리

이용걸,주용규,백락주,이호왕 고려대학교 의과대학 1990 고려대 의대 잡지 Vol.27 No.3

The etiologic agent of Korean hemorrhagic fever (KHF) was discovered in the lungs of Apodemus agrarius caught in Songnaeri, nearby Dongduchun city, Kyunggi province in 1976 which gave specific immunofluorescent reaction with convalescent sera from KHF patients for the first tune in Korea and it was named Hantaan virus after Hantaan river in 1980. In 1981, WHO adopted to call KHF, Hemorrhagic nephrosonephritis in Russia, Epidemic hemorrhagic fever in Japan and China, and Nephropathia epidemica in Scandinavia with compatible clinical symptoms as Haemorrhagic fever with renal syndrome (HFRS). Seoul virus, the second etiologic agent of KHF, was identified from lungs of wild urban rats caught in Seoul in 1982. Natural reservoirs of HFRS are not only field mice and laboratory rats but also wild urban rats in many parts of the world. This experiment was designed to find the distribution of infected urban rats with hanta-virus and to isolate hantavirus from antibody positive rats caught in Tokyo and Osaka city, Japan. Hantavirus antibodies and antigens were measured by the indirect immunofluorescent antibody technique and plaque reduction neutralization test. The results were as followings : 1. About 40% of wild urban rats in Tokyo city and 20% of Osaka city had antibodies against Hantaan virus. Hantavirus antigens were demonstrated in 8 lungs among the 59 wild urban rats collected in Tokyo. Six stram of Hantavirus were isolated in laboratory rats and tissue culture cells inoculated with the antigen positive lung suspensions of wild urban rats. 2. The Hantaviruses isolated from wild urban rats In Japan were well multiplied in S.D. rats but the viruses did not grow well in the striped field mice and Vero E6 cells. 3. Serum antibody titers of KHF patients, Nephropathia epidemica patients in Finland and epidemic hemorrhagic fever pabents in Japan were tested simultaneously against antigen preparations of viruses isolated from wild urban rats in Japan by indirect immunofluorescent antibody technique but there was no major differences. 4. As a result of comparing the viruses isolated from wild urban rats in Japan with other serotypes of hantaviruses by plaque reduction neutralization test in Vero E6 cells, the viruses were Seoul virus. The above results revealed that the viruses isolated from wild urban rats in Japan were Seoul virus and wild urban rats in Tokyo and Osaka city were infected with Seoul virus.

Gienohumeral Arthropathy After Arthroscopic Anterior Shoulder Stabilization

Rhee, Yong Girl,Lee, Dong-Hun,Chun, In Ho,Bae, Sung Chul KYUNG HEE UNIVERSITY MEDICAL CENTER 2005 고황의학상 수상논문집 Vol.21-22 No.-

Purpose: We present 5 cases of iatrogenic arthropathy after arthroscopic Bankart reconstruction using a metallic suture anchor. Type of Study: Retrospective case series. Methods: Five patients with pain and crepitus on motion were referred to our institution for further evaluation of the previous procedure on anterior shoulder instability. Screw-type metallic suture anchors were used in all cases. All patients were men, with an average age of 23 years (range, 21 to 26). Surgical records on previous procedure were reviewed, and the clinical symptoms were evaluated using a visual analogue scale (VAS), the Simple Shoulder Test (SST), and the Rowe scoring system. The secondary surgery for each patient was performed at an average of 12 months (range, 7 to 20) after the initial arthroscopic stabilization, except in one patient who wanted to postpone the revision surgery. Results: Protrusion of the anchor tip was seen in all and chondral defects in the humeral head with some degree of synovitis were also seen. Slight differences between preoperative and postoperative pain were seen, but almost no improvement in function, including range of motion, stability, and average Rowe score were seen after the second procedure. Patients who underwent revision surgery were dissatisfied with the final outcomes. Conclusions: Careful attention should be paid when using a metallic suture anchor. A secure, buried placement of the anchor is required in arthroscopic Bankart reconstruction. Poorly placed suture anchors may damage the glenohumeral joint, and if these are not corrected either at arthroscopic surgery or shortly after, the results can be suboptimal. If a patient complains of unusual mechanical symptoms after using anchors, radiographs should be performed. This kind of serious complication can be discovered earlier to prevent the severe destruction of the glenohumeral joint. Level of Evidence: Level Ⅳ.