• 대한기계학회:학술대회논문집
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• 대한기계학회 2007년도 춘계학술대회B
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• pp.2961-2966
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• 2007

When the pressure at the weak spot established at a certain part of a high pressure vessel or piping system exceeds a design pressure, this weak spot is burst, and the pressurized gas emitted through the weak spot will cause a compression wave system. In this connection, in the present study, an experimental study by using a conventional shock tube facility is performed to estimate the effects of the material of diaphragm, curvature radius and thickness of materials on the valve opening time in diaphragm. Pressure sensor having 500kHz in natural frequency is installed at 35mm downstream of the rupture diaphragm to measure the static pressure history of propagating and being accumulated compression wave. 4 kinds of materials are used as diaphragm that is aluminium, copper, stainless steel and zinc. The diaphragm radii of curvature R are ${\infty}$, 120mm and 60, respectively. And the depth for $90^{\circ}$ groove is 0.04mm. It is found that the smaller the tensile strength and elongation of the rupture diaphragm is, the smaller the radius of curvature of the rupture diaphragm is, and for the same conditions the thinner the thickness of the rupture diaphragm is, the shorter the valve opening time becomes. Also, the tensile strength, elongation and the radius of curvature of the rupture diaphragm for the same conditions are smaller, the maximum pressure rise caused by the coalescences of the compression wave is smaller. Finally the pressure ratio is higher, the valve opening time is shortened and gradient of pressure increment is more steepen.

• Journal of Chest Surgery
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• 제8권2호
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• pp.125-134
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• 1975

The record of 137 patients with spontaneous pneumothorax seen at Busan National University Hospital during past 3years were reviewed to study the possible pathogenesis and its effective management. and the results obtained as follows; 1] The incidence of the "spontaneous" pneumothorax which developed without underlying pathology was 13-1%. The majority of those cases was considered as the result of rupture of subpleural blebs. 2] The incidence of secondary pneumothorax which developed with underlying pathology was 50.0%, in which 42.3% was combined with pulmonary tuberculosis and 8, 0% was combined with pulmonary infection. The traumatic pneumothorax was developed in 36-5% of total series. 3] In age distribution, there was pronounced difference between spontaneous and secondary pneumothorax. The majority of spontaneous pneumothorax cases was 20-30 decade and tall and tall and thin in body structure. In secondary pneumothorax, however, the incidence was relatively high in age group more than 50 years old. 4] The incidence of pneumothorax combined with pulmonary tuberculosis was particularly high in our country, and the cause of pneumothorax was seemed due to the rupture of subpleural caseous foci in some cases, but the majority was seen due to the rupture of emphysematous blebs which were formed with a pathological process of chronic tuberculosis. 5]Closed [tube] thoracotomy was the main therapeutic approach of choice in the great majority ,of pneumothorax in our series with the relapse rate of 19.6%. However, open thoracotomy and adequate surgical procedures should be undertaken in patients with continuous air leakage over 7 days and recurrent attack of pneumothorax.

• Journal of Welding and Joining
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• 제8권4호
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• pp.27-34
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• 1990

Integranular corrosion behaviors of KAL (Knife Line Attack) and mechanical properties such as tensile and creep rupture were investigated for the tube material used for nearly 20 years under the condition of 463.deg. C and 28 $kg/cm^2$. Based and weld metal were austenitic stainless steel AISI 321 containing Ti, AISI 347 containing Nb, respectively. KLA is a kind of the intergranular corrosion which often occurs just near the HAZ (heat affected zone) of AISI 321 and AISI 347 stainless steel due to the grain boundary sensitization. In KLA zone, intergranular corrosion crack has propagated outwards from the inner surface and carbides of white and narrow band type assuming as (Cr, Fe) carbide were confirmed. All the delta-ferrite formed in the weld metal during weld solidification has been transformed into sigma-phase since delta-ferrte was exposed for 20 years at 463.deg. C. Elongation was very low at the range from room temperature to 600.deg. C and it was confirmed that creep-rupture properties were not consideralbly affected.

• 한국추진공학회지
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• 제25권6호
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• pp.20-28
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• 2021

극초음속 유동 시험에 활용되고 있는 충격파 터널 등은 원하는 시험 조건을 얻기 위해 격막의 파열 압력비를 맞추어 운용한다. 주로 금속 재질로 이루어진 격막은 정확한 압력비를 맞추기 위해 특정 형태로 가공하거나 강제 파열 장치를 사용하여 개방한다. 격막의 개방 과정은 수백 microsecond 동안 파열과 변형을 통해 이루어지는데, 동일한 압력비에서도 개방 정도와 개방 소요 시간에 따라 시험 조건이 달라질 수 있을 것으로 예상된다. 본 연구에서는 격막의 두께 및 재질 차이를 반영할 수 있는 파열모델을 적용하여 수치 해석을 수행하고 충격파의 형성과 정체 조건의 특성에 대해 살펴보았다. 격막 파열로 인해 생성된 충격파의 속도는 격막 개방 속도에 비례하였으며, 격막의 최종 개폐율 및 소요 시간에 따라 저압관 끝단에 형성되는 정체 압력과 시험 시간에 차이가 나타나는 것을 확인할 수 있었다.

• Journal of Chest Surgery
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• 제49권6호
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• pp.478-480
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• 2016

Spontaneous perforation of the esophagus after forceful vomiting is known as Boerhaave syndrome, a rare and life-threatening condition associated with a high rate of mortality. The management of Boerhaave syndrome is challenging, especially when diagnosed late. Herein, we report the successful management of late-diagnosed Boerhaave syndrome with T-tube drainage in a 55-year-old man. The patient was transferred to our institution 8 days after the onset of symptoms, successfully managed by placing a T-tube, and was discharged on postoperative day 46 without complications.

• Tuberculosis and Respiratory Diseases
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• 제40권4호
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• pp.449-453
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• 1993

A 64-year-old male was admitted due to abruptly developed, severe dyspnea via local clinic. He had been a heavy smoker and alcoholic for a long time. Chest PA showed huge haziness in right upper lung field. Sputum culture for bacteriology was positive for Klebsiella pneumoniae. Immediately, appropriate antibiotics were administered and artificial ventilation was started. On 40th hospital day, simple chest roentgenogram taken due to sudden aggravated dyspnea showed marked hyperlucency in right upper lung field, suggestive of rupture of abscess cavity and resultant pneumothorax. At that time, chest tube was inserted but air leakage from the chest tube persisted. Chest CT scan taken after chest tube insertion showed the tube inserted into a thin-walled cavity in the above lesion. on 84th hospital day, right upper lobectomy with decortication was performed. Pathologically, cavittary lung abscess was diagnosed on the findings of partial re-epithelialization of ciliated columnar epithelium with severe pulmonary vascular occlusion and extensive fibrous pleural adhesions.

• 대한기계학회논문집A
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• 제28권2호
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• pp.158-164
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• 2004

Steam generator tubes experience widespread degradations such as stress corrosion cracking, wear, tube rupture, denting, fatigue and so on. The resulting damages can cause tube bursting or leak of the primary water which contains radioactivity Therefore the allowable size of the damage is required to be determined on the maintenance purpose. The burst pressure of a tube with a T-type combination crack consisting of longitudinal and circumferential cracks is obtained experimentally and analytically. Fracture parameters such as stress intensity factor and crack opening angle are investigated. Also the burst pressure for a T-type combination crack is compared with that of a single longitudinal crack to develop a length-based criteria.

• Nuclear Engineering and Technology
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• 제54권5호
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• pp.1570-1578
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• 2022

During a severe accident, steam generator (SG) tubes undergo rapid changes in the pressure and temperature. Therefore, an appropriate creep model to predict a short term creep damage is essential. In this paper, a novel creep model for Alloy 690 SG tube material was proposed. It is based on the theta (θ) projection method that can represent all three stages of the creep process. The original θ projection method poses a limitation owing to its inability to represent experimental creep curves for SG tube materials for a large strain rate in the tertiary creep region. Therefore, a new modified θ projection method is proposed; subsequently, a master curve for Alloy 690 SG material is also proposed to optimize the creep model parameters, θ_i (i = 1-5). To adapt the implicit creep scheme to the finite element code, a partial derivative of incremental creep with respect to the stress is necessary. Accordingly, creep model parameters with a strictly linear relationship with the stress and temperature were proposed. The effectiveness of the model was validated using a commercial finite element analysis software. The creep model can be applied to evaluate the creep rupture behavior of SG tubes in nuclear power plants.

• Corrosion Science and Technology
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• 제23권3호
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• pp.246-254
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• 2024

Recently, coal-fired power plants are experiencing many problems that they have never experienced before due to an increase in flexible operation. In particular, a two-phase flow accelerated corrosion on water wall tubes in a boiler has not been detected overseas or domestically. There is no response plan to deal with such corrosion problem either. However, oxide film damage and tube material corrosion due to a two-phase flow accelerated corrosion are being discovered on water wall boiler tubes of domestic coal-fired power plants recently. If this situation is severe, it can cause enormous damage such as tube rupture. Therefore, in this paper, in order to prepare a response plan for a two-phase flow accelerated corrosion on water wall tubes in the future, differences between a two-phase flow accelerated corrosion and a single-phase flow accelerated corrosion were investigated and an example of discovery of a two-phase flow accelerated corrosion on water wall tubes was presented.

• 한국추진공학회:학술대회논문집
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• 한국추진공학회 2006년도 제27회 추계학술대회논문집
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• pp.367-370
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• 2006

Ballistic Range는 오래전부터 짧은 시간에 극도의 고압상태를 만들어낼 수 있기 때문에 고속 충격역학, 발사체 공기역학, 새로운 재료의 생성과 같은 다양한 공학 분야에서 사용되어왔다. 2단 경 가스총은 가장 넓게 사용되어지고 있다. 현재의 실험적 연구는 발사체 가상실험을 쉽게 수행할 수 있는 새로운 타입의 Ballistic Range를 개발하기 위해 진행되어져왔다. Ballistic Range은 고압튜브, 피스톤, 펌프튜브, 충격튜브, 발사튜브로 구성된다. 펌프튜브와 발사튜브사이에 충격튜브의 삽입의 효과는 조사중이다. 실험은 발사체 속도의 다양한 변수들의 의존성을 찾기 위해 수행되었다. 고압튜브압력, 격막파열압력, 발사체질량은 다양한 발사체 속도를 얻기 위해 변화를 주었다. 저자의 이론적 연구를 통해 얻는 결과값과 실험적 결과값을 비교해보기로 한다.