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Zirconium 합금 관 임계좌굴 압력의 불확실성에 따른 최소안전율
김형규(Hyung-Kyu Kim),김재용(Jae-Yong Kim),윤경호(Kyung-Ho Yoon),이영호(Young-Ho Lee),이강희(Kang-Hee Lee),강흥석(Heung-Seok Kang) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11
Uncertainty of the elastic buckling formula of a thin tube is considered. The measuring uncertainty of Young’s modulus and Poisson’s ratio and the tolerance of the tube thickness and diameter are dealt with. The elastic buckling should be absolutely prohibited for a thin tube like a nuclear fuel rod that should satisfy a self-stand criterion. Since the predicted critical buckling pressure overestimated the actual one observed from an experiment, determination of the minimum safety factor is crucial. The uncertainty of each parameter (i.e., Young’s modulus, Poisson’s ratio, thickness and diameter) is mutually independent, so the safety factor is evaluated as the sum of the inverse of each uncertainty. It is found that the thickness variation strongly affects the uncertainty. The minimum safety factor of a thin tube of Zirconium alloy needs to be from 1.547 to 3.487 for the thickness of 0.87 and 0.254 ㎜, respectively.
지르코늄 합금 관의 임계좌굴 압력 산정을 위한 최소안전율
김형규(Hyung-Kyu Kim),김재용(Jae-Yong Kim),윤경호(Kyung-Ho Yoon),이영호(Young-Ho Lee),이강희(Kang-Hee Lee),강흥석(Heung-Seok Kang) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.3
얇은 관 탄성좌굴 공식의 불확실성을 고려하기 위해, 공식을 구성하는 파라미터인 튜브재료의 탄성계수, 푸아송 비, 튜브 두께 및 지름의 불확실성을 분석하였다. 본 연구는 원자로에서 연소되는 핵연료봉과 같이 사용 중 함몰을 엄격히 방지하고 있는 얇은 관의 설계신뢰도를 향상시키는 데에 중요하다. 분석 방법은 각각의 파라미터가 변화할 수 있는 범위를 충분히 포함할 수 있는 최소의 탄성좌굴 안전율을 구하고 이를 선형적으로 합하여 최종의 최소안전율을 구하였다. 최소 안전율에 가장 큰 영향을 미치는 파라미터는 관의 두께로 나타났다. 두께가 얇을수록 더 큰 최소안전율이 필요하며 예로 적용한 지르코늄 합금관의 경우, 두께가 0.254 와 0.87 ㎜ 일 때 최소안전율은 각각 1.547 과 3.487 로 나타났다. We consider the uncertainty in the elastic buckling formula for a thin tube. We take into account the measurement uncertainty of Young’s modulus and Poisson’s ratio and the tolerance of the tube thickness and diameter. Elastic buckling must be prohibited for a thin tube such as a nuclear fuel rod that must satisfy a self-stand criterion. Since the predicted critical buckling pressure overestimated that found in the experiment, the determination of the minimum safety factor is crucial. The uncertainty in each parameter (i.e., Young’s modulus, Poisson’s ratio, thickness, and diameter) is mutually independent, so the safety factor is evaluated as the sum of the inverse of each uncertainty. We found that the thickness variation greatly affects the uncertainty. The minimum safety factor of a thin tube of Zirconium alloy is evaluated as 1.547 for a thickness of 0.87 ㎜ and 3.487 for a thickness of 0.254 ㎜.
김형규(Hyung-Kyu Kim),김재용(Jae-Yong Kim),이강희(Kang-Hee Lee),윤경호(Kyung-Ho Yoon),강흥석(Heung-Seok Kang),이영호(Young-Ho Lee) 대한기계학회 2013 대한기계학회 춘추학술대회 Vol.2013 No.12
A complete contact problem of bonded condition is studied. Asymptotic analysis for a sharp notch problem is extended to incorporate the conditions of elastic dissimilarity and contact angle variation. Stress singularity at the contact corner is expressed by the generalized stress intensity factors (GSIFs) of mode I and II, with which a stress equation is described. Mode decoupling method is suggested to obtain the GSIFs. The characteristics of angular function in the stress equation are discussed. A simple example is solved to obtain the actual GSIFs with the assistance
김형규(Hyung-Kyu Kim),윤경호(Kyung-Ho Yoon),이영호(Young-Ho Lee),김재용(Jae-Yong Kim),이강희(Kang-Hee Lee) 대한기계학회 2008 대한기계학회 춘추학술대회 Vol.2008 No.5
Applicability of the contact mechanics theory is investigated for the contact. and internal stresses of a toroidal seal. An actual component of the toroidal seal is an elastomeric O-ring, which is widely used in the mechanical system. Lindley's previous study is consulted to analyze the present problem within the regime of elasticity. Two cases of loading condition are considered: ⅰ) top and bottom of the seal are compressed, and ⅱ) laterally restrained with internal pressure in addition to case ⅰ). As a result, an approximation method for the contact and internal stresses is suggested with accommodating the correction factors of the contact length and peak contact stress to the Hertz formula. A method of experimental verification is discussed.
신장 이식 환자에서 CMV duodenitis 치료 후 병발한 Pneumocystis jirovecii 폐렴 1예
김혜원 ( Hye Won Kim ),김명규 ( Myung Gyu Kim ),우영석 ( Young Seok Woo ),부창수 ( Cang Soo Boo ),조상경 ( Sang Kyung Jo ),김형규 ( Hyoung Kyu Kim ),조원용 ( Won Yong Jo ),이광균 ( Kwang Gyun Lee ),김혜옥 ( Hye Ok Kim ),오초롱 ( C 대한신장학회 2008 Kidney Research and Clinical Practice Vol.27 No.5
Solid organ transplant recipients are at increased risk for various opportunistic infections because of their immunocompromised state. Pneumocystis jirovecii (carinii) infection has posed serious problems in these patients which can be life threatening. It has been reported that incidences of Pneumocystis infection have dramatically decreased with the use of prophylactic antibiotics. However, there have been reports that say the risks of Pneumocystis infection are increasing with the use of new immunosuppressive drugs and in presence of preceding immunomodulating infections such as CMV infection which is another common opportunistic infection in transplant patients. There were only a few case reports abroad on Pneumocystis infection following CMV infection in patients who underwent kidney transplantation. In Korea, however, there hasnt been any report of such cases. Herein we report a case of a kidney transplant patient who experienced a serious episode of Pneumocystis jirovecii pneumonia following CMV duodenitis. After adequate mechanical ventilation and use of antibiotics the patient completely recovered without any complications.
김형규(Hyung-Kyu Kim),이영호(Young-Ho Lee),허성필(Sung-Pil Heo),윤경호(Kyung-Ho Yoon),강홍석(Heung-Seok Kang),송기남(Kee-Nam Song) 한국트라이볼로지학회 2003 한국트라이볼로지학회 학술대회 Vol.36 No.-
Studied is the characteristic of wear shape in fuel fretting experiment. Two different shapes are used for the grid spring which is in contact with the cladding tube. The contours of the two springs are concave in transverse and flat in axial direction (type A) and convex in transverse and axial directions (type B). Both are designed for restraining fretting wear damage by increasing the contact area. Experiment is conducted in air and water at room temperature with various slip ranges and two (10N, 30N) contact loads. The result shows that the increase of wear scar width is distinct in the case of type A spring as the slip range increases, while that of wear length is considerable in the case of type B spring as the slip range and load increase. Third body abrasion can explain this phenomenon. Wear dimension is almost always greater in water environment, which shows the role of water is accelerator of debris removal rather than lubricant in fuel fretting together with the result of severer wear volume in water previously found[5].
김형규(Hyung-Kyu Kim),허성필(Sung-Pil Heo),강흥석(Heung-Seok Kang),윤경호(Kyung-Ho Yoon),송기남(Kee-Nam Song) 대한기계학회 2002 대한기계학회 춘추학술대회 Vol.2002 No.5
Studied are the deformation shape and the traction of a thin strip structure, which is in contact with a rigid<br/> cylinder. Finite element (FE) analysis is carried out to investigate the change in shape and traction during the<br/> increase of the load using the code, ABAQUS. It is found that the traction begins with Hertzian profile as the<br/> load is applied, and is changed to have the similar shape induced by the rounded punch as the load increases.<br/> This implies that the contact shape should be carefully investigated even in the period of the load increase for<br/> correct contact analysis. The analytical solution in the case of the contact with rounded punch is also<br/> discussed with the FE result.