• 대한기계학회:학술대회논문집
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• 대한기계학회 2000년도 추계학술대회논문집A
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• pp.99-104
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• 2000

This paper describes the high temperature creep characteristics for virgin material of 9Cr1MoVNb steel using small punch creep(SP-Creep) test technique which is developing recently. In addition, the several results of SP-Creep test are compared with that of 2.25Cr- 1Mo steel which is widely used as boiler materials and that of conventional uniaxial creep test. The obtained SP-Creep curves show the creep behaviors of three regimes like that obtained from conventional uniaxial creep test, and SP-Creep properties are definitely depended on applied load and test temperature. The correlation of SP-Creep rate and creep rupture life with applied load has been determined like the correlation between creep rate/rupture life and stress in uniaxial creep test, and also is satisfied with Power law. The creep rupture times of newly 9Cr1MoVNb steel are higher than those of 2.25Cr1Mo steel at the same creep temperature and applied loading condition, and the decrease extent of creep rupture life with loads is very lower compared with 2.25Cr1Mo steel.

• Nuclear Engineering and Technology
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• 제46권6호
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• pp.817-824
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• 2014

To ensure the safety of research reactors, the water level must be maintained above the required height. When a pipe ruptures, the siphon phenomenon causes continuous loss of coolant until the hydraulic head is removed. To protect the reactor core from this kind of accident, a siphon breaker has been suggested as a passive safety device. This study mainly focused on two variables: the size of the pipe rupture and the timing of air entrainment. In this study, the size of the pipe rupture was increased to the guillotine break case. There was a region in which a larger pipe rupture did not need a larger siphon breaker, and the water flow rate was related to the size of the pipe rupture and affected the residual water quantity. The timing of air entrainment was predicted to influence residual water level. However, the residual water level was not affected by the timing of air entrainment. The experimental cases, which showed the characteristic of partical sweep-out mode in the separation of siphon breaking phenomenon [2], showed almost same trend of physical properties.

• 한국항공우주학회지
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• 제42권9호
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• pp.745-751
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• 2014

멀티 노즐로 구성된 추진기관의 경우, 각 노즐별 노즐마개 파열압력의 편차가 초기 분력을 유발하고 유도탄의 비행안정성에 영향을 미친다. 따라서 노즐마개 설계 시 먼저 형태별로 파열거동을 분석하여 원하는 파열압력에서 균일하게 파열되는지를 확인해야 한다. 본 연구에서는 평판형, "+" 노치형 노즐마개에 대한 파열거동을 실험적, 해석적인 방법으로 분석하였다. 실험 시 저장온도, 노치의 유무, 노치방향에 따른 노즐마개 파열압력 및 편차를 분석하였다. 그리고 유한요소해석을 통해 노즐마개의 파열거동을 순차적으로 분석하고, 그 결과를 실험값과 비교하여 정확성을 검증하고자 하였다. 해석 시 상용프로그램인 Abaqus/Explicit를 사용하였고, 파손모델은 Johnson-cook 전단파손모델을 적용하였다.

• 항공우주기술
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• 제11권2호
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• pp.122-128
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• 2012

액체 로켓 엔진 점화 라인에 부착되는 연소기 점화기 중에 양단에 파열판이 부착되는 방식이 있다. 본 연구에서는 전단에 솔레노이드밸브가 있는 이러한 연소기 점화기에 대한 유량계수 시험을 수행하였다. 방사형 및 원주형 스코어를 가지는 인장형 파열판, 점화기에 대한 상온 수류 시험을 통하여, 유량계수에 대한 스코어, 유량, 파열판 두께, 전단 공기층 및 솔레노이드밸브의 영향을 살펴보았다.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2004년도 추계학술대회 논문집
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• pp.22-27
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• 2004

Super-duralumin has widely been used as the part materials of aerospace and automobile industry because it has high specific strength and also is light. But, we have little design data about the creep behaviors of the alloy. Therefore, in this study, every creep test under four constant stress conditions have been conducted for four temperature conditions. A series of creep tests had been performed to get the basic design data and life prediction of super-duralurnin products and we have gotten the following results. First, the stress exponents showed the descending trend as the test temperatures increase. Secondly, the creep activation energy gradually decreased as the stresses become bigger. Thirdly, the constant of Larson-Miller parameters on this alloy was estimated about 6. And last, the fractographs at the creep rupture showed both the brittle fracture due to the transgranular rupture.

• Journal of Chest Surgery
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• 제26권11호
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• pp.838-844
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• 1993

Rupture of aortic is for the most part a terminal disorder and requires prompt and aggressive treatment. Most of the patients who develop this condition outside the hospital die before appropriate therapy can be instituted. Thus prompt treatment, sometimes innovative, resulted in a highly significant survival rate. We experionced 21 aortic rupture due to mycotic aneurysm and another 3 due to chest trauma. Operation was done in 11 cases, and mortality was 3 of 11 cases. In another 10 cases, operation was not performed and all of them were expired. We confirmed diagnosis using only non invasive technic as ultrasonogram and computed tomography and invasive technic like aniography was absolutely avoided. Preoperative management was aimed to lower blood pressure for the purpose of preventing srcondary bleeding, and operantions erer porformed promptly if possible.

• Journal of Trauma and Injury
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• 제26권4호
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• pp.316-318
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• 2013

Rupture of the esophagus after blunt trauma is a rare event. But any type of esophageal rupture has the high morbidity and mortality rate. In these situations, the sign and symptom of the esophageal rupture is subtle and nonspecific; therefore, the physicians are usually not suspicious. Delaying in diagnosis prevents proper treatment (surgical or non-surgical) before significant complications occurred. We report a case of a cervical esophageal perforation with primary repair and drainage after blunt trauma.

• Journal of Korean Neurosurgical Society
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• 제59권1호
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• pp.11-16
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• 2016

Objective : We conducted a retrospective cohort study to elucidate the natural course of unruptured intracranial aneurysms (UIAs) at a single institution. Methods : Data from patients diagnosed with UIA from March 2000 to May 2008 at our hospital were subjected to a retrospective analysis. The cumulative and annual aneurysm rupture rates were calculated. Additionally, risk factors associated with aneurysmal rupture were identified. Results : A total of 1339 aneurysms in 1006 patients met the inclusion criteria. During the follow-up period, 685 aneurysms were treated before rupture via either an open surgical or endovascular procedure. Six hundred fifty-four UIAs were identified and not repaired during the follow-up period. The mean UIA size was $4.5{\pm}3.2mm$, and 86.5% of the total UIAs had a largest dimension <7 mm. Among these UIAs, 18 ruptured at a median of 1.6 years (range : 27 days to 9.8 years) after day 0. The annual rupture risk during a 9-year follow-up was 1.00%. A multivariate Cox proportional hazards analysis revealed that the aneurysm size and a history of subarachnoid hemorrhage (SAH) were statistically significant risk factors for rupture. For an aneurysms smaller than 7 mm in the absence of a history of SAH, the annual rupture risk was 0.79%. Conclusion : In our study, the annual rupture risk for UIAs smaller than 7 mm in the absence of a history of SAH was higher than that of Western populations but similar to that of the Japanese population.

• 대한기계학회논문집
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• 제13권2호
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• pp.236-242
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• 1989

본 연구에서는 주로 보일러의 과열기 및 재열기등의 관재료로 널리 사용되고 있는 304 스테인레스강에 대하여 실제 고온부식현상을 재현한 부식환경하인 630.deg. C, 690.deg. C 및 750.deg. C 3가지 온도범위에서 크리프시험을 실시하고 고온부식이 크리프파단 특성에 미치는 영향을 부식조건이 없는 고온대기중의 실험결과와 비교 검토하였다.

• 대한족부족관절학회지
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• 제27권1호
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• pp.12-16
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• 2023

Purpose: Postoperative exercise for acute Achilles tendon rupture is important for a patient's return to daily life and sports. On the other hand, the protocol requires considerable effort to educate patients and continuous checking. This study evaluated the outcome of a new simple and delayed rehabilitation protocol after Achilles tendon rupture repair. Materials and Methods: From July 2014 to November 2020, one hundred eighty-three patients were operated on by one surgeon. The exercise protocol was classified into two methods. One group (immediate protocol, control group) started immediate full weight bearing with a 20° plantar flexion range of motion from two days postoperatively. Ankle dorsiflexion was restricted to 0°. The other group (delayed protocol, case group) started full weight bearing with a controlled ankle motion boot from two weeks postoperatively. No range of motion exercise was allowed until six weeks postoperatively. Age, sex, body mass index, ankle range of motion, muscle power, time to return to previous physical activity, functional score, and complication rate were evaluated. The results of the two groups were compared using a Mann-Whitney test. Statistical significance was set as p<0.05. Results: The range of motion, double heel rising, and one-leg standing were achieved faster in the control group (p<0.05). However, single-heel rising, repeated single-heel rising, return to previous activity (work, run, and sport), and functional scores showed no statistical difference (p>0.05). Conclusion: Simple and delayed postoperative rehabilitation of acute Achilles tendon rupture without active range of motion exercises showed satisfactory functional results and a low complication rate.