• 대한기계학회논문집A
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• 제24권10호
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• pp.2597-2602
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• 2000

The most effective means of evaluating remaining life is through the creep testing of samples removed from the component. But sampling of large specimen from in-service component is actually impossible. So, sampling device and small-specimen creep tester have been applied. Sampling device has been devised to extract mechanically small samples by hemispherical, diamond -coated cutter from the surface of turbine rotor bores and thick-walled pipes without subsequent weld repairs requiring post weld heat treatment. A method of manufacturing small creep specimen, 2min gage diameter and 10min gage length, using electron beam welding to attach grip section, has been proven. Small-specimen creep tester has been designed to control atmosphere to prevent stress increment by oxidation during experiment. To determine whether the small specimens successfully reproduce the behavior of large specimens, creep rupture tests for small and large specimens have been performed at identical conditions. Creep rupture times based on small specimens have closely agreed within 5% error compared with that of large specimen. The errors in rupture time have decreased at longer test period. This comparison validates the procedure for fabricating and testing on small specimen. This technique offers potential as an efficient method for remaining life assessment by direct sampling from in -service high temperature components.

• 한국재료학회지
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• 제31권5호
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• pp.255-263
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• 2021

P91 steel has been a highly researched material because of its applicability for high-temperature applications. Considerable efforts have been made to produce experimental creep data and develop models for creep life prediction. As creep tests are expensive and difficult to conduct, it is vital to develop authenticated empirical methods from experimental results that can be utilized for better understanding of creep behavior and can be incorporated into computational models for reliable prediction of creep life. In this research, a series of creep rupture tests are performed on the P91 specimens within a stress range of 155 MPa to 200 MPa and temperature range of 640 ℃ (913 K) to 675 ℃ (948 K). The microstructure, hardness, and fracture surfaces of the specimens are investigated. To analyze the results of the creep rupture tests at a macro level, a parameter called creep work density is derived. Then, the relationships between various creep parameters such as strain, strain rate, time to rupture, creep damage tolerance factor, and creep work density are investigated, and various empirical equations are obtained.

• 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.

• Journal of Korean Neurosurgical Society
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• 제59권1호
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• pp.6-10
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• 2016

Objective : The objectives of this study was to determine the incidence and outcomes of procedural rupture (PR) during coil embolization of unruptured intracranial aneurysm (UIA) and to explore potential risk factors. Methods : This retrospective study evaluated 1038 patients treated with coil embolization between January 2001 and May 2013 in a single tertiary medical institute. PR was defined as evidence of rupture during coil embolization or post procedural imaging. The patient's medical records were reviewed including procedure description, image findings and clinical outcomes. Results : Twelve of 1038 (1.1%) patients showed PR. Points and time of rupture were parent artery rupture during stent delivery (n=2), aneurysm rupture during filling stage (n=9) and unknown (n=1). Two parent artery rupture and one aneurysm neck rupture showed poor clinical outcomes [modified Rankin Scale (mRs) >2] Nine aneurysm dome rupture cases showed favorable outcomes ($mRS{\leq}2$). Location (anterior cerebral artery) of aneurysm was associated with high procedural rupture rate (p<0.05). Conclusion : The clinical course of a patientwith procedural aneurysm rupture during filling stage seemed benign. Parent artery and aneurysm neck rupture seemed relatively urgent, serious and life threatening. Although the permanent morbidity rate was low, clinicians should pay attention to prevent PR, especially when confronting the anterior cerebral artery aneurysm.

• 대한기계학회논문집
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• 제18권11호
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• pp.2837-2845
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• 1994

Several methods have been developed to predict on the remaining life of the old power plants. However, Larson-Miller parameter, one of existing creep life prediction methods, has not reflected the effect of material degradatioin and grain size. So this study has been carried out to research the effects of material degradation and austenite grain coarsening on the life prediction of 3.5Ni-Cr-Mo-V steel. An experimental result shows that carbide coarsening has no significant effects on the creep rupture life and the Larson-Miller parameter, but grain coarsening has an important influence on the creep ruptrure life and the Larson-Miller parameter. Therefore Larson-Miller constant, K should be determined to consider on the chemical composition and the grain size of materials.

• Journal of Trauma and Injury
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• 제30권4호
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• pp.235-237
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• 2017

Hepatic hemangioma is the most frequently occurring benign tumor of the liver. Hepatic hemangioma rupture is a rare phenomenon, which can lead to life-threatening conditions. Here, we report a case of hepatic hemangioma rupture caused by blunt trauma. Explorative laparotomy was performed due to unstable vital signs and abdominal massive hemoperitoneum revealed on computed tomography. We detected arterial bleeding from a hepatic hemangioma and performed primary suture of the liver and postoperative angiographic embolization.

• Journal of Trauma and Injury
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• 제27권2호
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• pp.38-42
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• 2014

Traumatic diaphragmatic rupture is quite uncommon and rarely lethal injury. However, delayed presentation between the injury and the diagnosis can cause a life-threatening condition with various complications such as intestinal hernia, obstruction, strangulation, respiratory distress. Here, we present a case of delayed presentation of traumatic diaphragmatic rupture in a 51-year-old man, and then discuss about the clinical implication of delayed presentation of diaphragmatic rupture with a review.

• Journal of Trauma and Injury
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• 제31권1호
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• pp.16-18
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• 2018

Delayed esophageal rupture due to blunt injury is not new. However, rupture due to suspected barotrauma is very rare. We describe a case of esophageal rupture in a male 24-year-old patient after diving in shallow waters. The patient was quadriplegic and could not experience the typical chest pain related to rupture and resulting mediastinitis. The rupture was discovered 4 days after emergency decompressive laminectomy and fusion for his cervical spine. The rupture was evidently caused by barotrauma and was discovered four days after admission. He underwent primary closure and pericardial flap as a life-saving procedure.

• Journal of Mechanical Science and Technology
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• 제19권7호
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• pp.1432-1440
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• 2005

High-temperature rupture behavior of 5083-Al alloy was tested for failure at 548K under multiaxial stress conditions: uniaxial tension using smooth bar specimens, biaxial shearing using double shear bar specimens, and triaxial tension using notched bar specimens. Rupture times were compared for uniaxial, biaxial, and triaxial stress conditions with respect to the maximum principal stress, the von Mises effective stress, and the principal facet stress. The results indicate that the von Mises effective and principal facet stresses give good correlation for the material investigated, and these parameters can predict creep life data under the multiaxial stress states with the rupture data obtained from specimens under the uniaxial stress. The results suggest that the creep rupture of this alloy under the testing condition is controlled by cavitation coupled with highly localized deformation process, such as grain boundary sliding. It is also conceivable that strain softening controls the highly localized deformation modes which result in cavitation damage in controlling rupture time of this alloy.

• 한국공작기계학회논문집
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• 제11권4호
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• pp.54-61
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• 2002

Inconel 690 alloy has widely been used in power plant and high temperature facilities because it has high thermal resistance and toughness. But we have little design data about the creep behaviors of the alloy. Therefore, in this study, an apparatus has been designed and built for conducting creep tests under constant load conditions. A series of creep tests on Inconel 690 alloy have been performed to get the basic design data and life prediction of inconel products and we have gotten the following results. First, the stress exponents decrease as the test temperatures increase. Secondly, the creep activation energy gradually decreases as the stresses become bigger. thirdly, the constant of Larson-Miller Parameters on this alloy is estimated about 10. And last the fractographs at the creep rupture show both the ductile and the brittle fracture according to the creep conditions.