극저온용 구조재료의 파괴인성평가법에 관한 연구

권일현,정세희,Kwon, Il-Hyun,Chung, Se-Hi 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.1

This paper was undertaken to develop the fracture toughness testing method using small and single specimen compared to the conventional method in evaluating elastic-plastic fracture toughness of the superconducting magnet structural material at cryogenic temperature. The elastic-plastic fracture toughness test was conducted by using the unloading compliance method recommended by ASTM E813-89 to accomplish the above purpose. And, the 20% side-grooved 0.5TCT and 1TCT specimens were used to evaluate the fracture toughness by using as possible as miniaturized CT specimen. The unloading compliance method was a very useful method in evaluating elastic-plastic fracture toughness at cryogenic temperature. It could be taken valid fracture toughness values by using 20% side-grooved 0.5TCT specimen recommended by ASTM E813-89.

전기화학적 재활성화 분극시험에 의한 터빈부재의 열화손상 평가

권일현,백승세,류대영,유효선,Kwon, Il-Hyun,Baek, Seung-Se,Lyu, Dae-Young,Yu, Hyo-Sun 대한기계학회 2002 大韓機械學會論文集A Vol.26 No.7

The extent of materials deterioration can be evaluated accurately by mechanical test such as impact test or creep test. But it is almost impossible to extract a large test specimen from in-service components. Thus material degradation evaluation by non-destructive method is earnestly required. In this paper, the material degradation for virgin and several aged materials of a Cr-Mo-V steel, which is an candidated as structural material of the turbine casing components for electric power plant, is nondestructively evaluated by reactivation polarization testing method. And, the results obtained from the test are compared with those in small punch(SP) tests recommended as a semi-nondestructive testing method using miniaturized specimen. In contrast to the aged materials up to 1,000hrs which exhibit the degradation behaviors with increased ${\Delta}[DBTT]_{SP}$, the improvement of mechanical property can be observed on the 2,000hrs and 3,000hrs aged materials. This is because of the softening of material due to the carbide precipitation, the increase of ferritic structures and the recovery of dislocation microstructure by long-time heat treatment. The reactivation rates($I_R/I_{Crit},\;Q_R/Q_{Crit}$) calculated by reactivation current densityt ($I_R$) and charge($Q_R$) in the polarization curves exhibit a good correlation with ${\Delta}[DBTT]_{SP}$ behaviors.

고질소계 강의 열처리재 및 용접부의 기계적성질 저하에 관한 연구

권일현,윤재영,정세희 대한용접접합학회 1998 대한용접·접합학회지 Vol.16 No.3

The degradation of mechanical properties in the high nitrogen steel HN3 developed for nuclear fusion reactor has been evaluated quantitatively using the small punch(SP) test, X-ray diffraction (XRD) analysis has also been conducted to identify carbides or nitrides precipitated on grain boundaries of the heat treated samples. Mechanical properties of the steel HN3 significantly decreased with increasing heat treatment time and temperature or with decreasing testing temperature. Combination of XRD and metallurgical observation, revealed that the material degradation in the thermally aged steel was caused by precipitation of carbides on the grain boundaries. While the weld metal showed the lowest mechanical properties among various microstructures in GTA weldments. By combining SP test and XRD analysis, cryogenic fracture behaviors and aging degradation for high nitrogen steel could be successfully evaluated in nondestructive manner.

전기화학기법에 의한 슈퍼 오스테나이트 스테인리스강의 열화손상 평가 ( An Evaluation of Degraded Damage for Superaustenitic Stainless Steel by Electrochemical Polarization Technique )

권일현,이송인,백승세,이종기,Y. Iino,유효선 대한기계학회 2001 대한기계학회 춘추학술대회 Vol.2 No.1

소형펀치 시험법에 의한 초전도 마그넷 구조용강 TIG 용접부의 극저온 파괴특성 평가

권일현,정세희,T. Hashida 대한용접접합학회 1996 대한용접·접합학회지 Vol.14 No.5

In order to evaluate the cryogenic fracture characteristics of structural steels for superconducting magnets of fusion reactor, small punch (SP) testing was performed on austenitic stainless steel (JN1 base metal) and its TIG weldments at 293K, 77K and 4K. The mechanical properties with respect to the extracted location of the weld metal, on the effects of welding heat cycle about base metal near fusion line in TIG weldments were investigated. The mechanical property of the weld metal in TIG weldments depends on distance from welding root, root region of weldments having the lowest mechanical property. The base metal near fusion line showed degradation of mechanical property caused by cyclic heating during the TIG welding. Based on the test results, HAZ was found to be up to 5mm from the fusion line. It is shown that SP testing is a useful tool to evaluate the mechanical properties with respect to the microstructures changes such as HAZ as well as weld metal in TIG weldments at cryogenic temperature.

무급유 베어링 최적 소결조건 도출을 위한 첨가제에 따른 겉보기 기공률 특성 평가

권일현,이정권 한국기계기술학회 2017 한국기계기술학회지 Vol.19 No.5

The object of this paper is to examine the optimum sintering condition which have excellent mechanical properties compared to the conventional oilless bearing. It is shown that the sintering rate is the most excellent at 850°C, especially KAB-23, KAB-23G, PBF-8 specimens. With increasing the nitrogen injection rate, the apparent porosity increased gradually. In contrast, with increasing the hydrogen injection rate, the apparent porosity decreased gradually. It is shown that the apparent porosity is very useful in the range of nitrogen injection rate 2Nm 3 and hydrogen injection rate 10Nm3 .

핵 융합로 구조재료의 예민화 열처리에 따른 극저온 파괴거동 및 분극특성

권일현,정세희,Kwon, Il-Hyun,Chung, Se-Hi 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2

The cryogenic fracture behaviors of austenitic stainless steel HN2 developed for nuclear fusion reactor were evaluated quantitatively by using the small punch(SP) test. The electrochemical polarization test was applied to study thermal aging degradation of HN2 steel. The X-ray diffraction(XRD) analysis was conducted to detect carbides and nitrides precipitated on the grain boundary of the heat treated HN2 steel. The mechanical properties of the HN2 steel significantly decreased with increasing time and temperature of heat treatment or with decreasing testing temperature. The integrated charge(Q) obtained from electrochemical polarization test showed a good correlation with the SP energy(ESP) obtained by means of SP tests. From the results observed in the x-ray diffraction and anodic polarization curve, it was known that the material the grain boundary. Combining SP test and electrochemical polarization test, it could be useful tools to non-destructively evaluate the cryogenic fracture behaviors and the aging degradation for cryogenic structural material.

첨가제 및 소결조건에 따른 무급유 베어링 강판 기공성 평가

권일현,이정권 한국기계기술학회 2018 한국기계기술학회지 Vol.20 No.3

Recently, the interest in the development of Oilless bearings, which is a kind of sliding bearing, has been attracting to industry. Oilless bearings are mainly used in areas where fluid lubrication is difficult to apply because of large contact area. The purpose of this study is to develop products with higher load and durability compared to the conventional oilless bearing. For this purpose, the optimal steel sheet was obtained and the porosity evaluation was carried out by evaluating bronze sinterability for various steel sheets. The conclusion obtained is as follows.; It was found that steel plate suitable for bronze powder plate is SPCC CR (Cold Rolled). The average porosity of KAG-23, KAG-23G and PBF-8 specimens was 16.8%, 17.8% and 22.1%, respectively, indicating that the porosity of PBF-8 specimen was the highest. As the number of rolling increases, the surface porosity decreases rapidly.

한국민화에 나타난 보자기의 기능과 탈근대적 의미

권일현,최법진 한국일러스트레이션학회 2010 일러스트레이션 포럼 Vol.11 No.22

본 연구는 디자인은 공동체의 실생활에 뿌리박은 삶의 표현이라는 점을 전제로 디자인의 보편성을 넘어 민족공동체성을 부활시켜 디자인을 이해한다. 이를 위하여 한국의 실생활문화에 의해 만들어졌고, 그 생활을 구성한 보자기를 탐구한다. 보자기에 담겨진 한국 공동체의 디자인 철학을 이해하고 보자기의 사유가 어떻게 현대 통섭의 논의에 맞추어 적절하게 이해될 수 있는가를 살핀다. 근대성의 제도와 이념이 우선시 되는 산업사회에서는 자연환경과 인간적 가치가 기계적 규격주의에 의해 소외될 수밖에 없다. 보자기는 고문서와 민화에서 보여 지듯이, 언제, 어디서나 자유롭게 활용 가능한 기능을 지님으로서 유비쿼터스 시대 디자인의 방향을 제시한다. 문헌과 민화가 드러내듯이, 한국보자기의 통섭적 특성은 기능의 차원에서 발휘된다. 가변성과 융통성을 기본으로 한다. 이른 바, 통섭적 제품으로서 실제 쓰임새와 철학을 지니고 있다. 또한 사용자의 차원에서 보더라도 남녀노소, 계층에 가릴 것 없이 폭넓은 통섭적 소통을 이루어 낸다. 특히 재사용성과 활용의 생태적인 특성은 보자기의 환경주의적 특성이라 할 것이다. 보자기는 다기능성과 장식성, 범용성과 생태성을 두루 갖춘 통섭적 가치를 지닌다는 점에서 현대디자인의 미래를 논할 수 있게 한다. The new paradigm of contemporary design can be understood and led by Korean Philosophy of Wrappers. Modern design goes on without any sincerity on the concept of "convergence" or "consilience". I illustrate Korean wrappers' functions for understanding this concept in the theoretical perspective. The design has its history which is in company with the industrial process of Capitalist society. The industrial society has eliminated, little by little our communicative substances of design activities and enriched its effectiveness for the production only. I examine the design convergences through Korean wrappers' functions and philosophies. Approach method is a comparative analyse among wrappers' functions though Korean(Chosun) vernacular paintings. After the analyse, I exposed the communicative nature of Korean wrapper. The wrapper has 3 kinds of communication with the nature: wrapper itself, circumstances and recycling. 1) It has divers functions much more than a modern bag, Multi-functional by nature, the Korean wrapper give us some reflections on design functionality of the future. 2) The Korean wrapper is not only material one and a result of citizens' communication. It produce a common usage for everyone for a society. 3) The Korean wrapper can be reused and go into the recycling system of the nature. The Korean wrapper gives us two important perspectives related each other: realization of multi-functional design which we need in 21th century and constructing the identity between the nature and design itself.

단일 시험편법에 의한 극저온용 구조재료의 파괴인성 저하에 관한 연구

권일현,Kwon, Il-hyun 대한기계학회 1998 大韓機械學會論文集A Vol.22 No.2

This paper was investigated degradation of the fracture toughness caused by sensitizing heat-treatment of the cryogenic structural material JN1 base metal using unloading compliance method reported as useful a method in evaluating the elastic-plastic fracture toughness at cryogenic temperature. The specimens used in this paper were 20% side-grooved 0.5T-CT specimens which were machined in the JN1 base metal. Also, to investigate cryogenic fracture toughness of the fusion line region in the JN1 GTA weldments, it was also used 20% side-grooved 0.5T-CT specimens that was machined fusion line to located in the middle of the specimen. The cryogenic fracture toughness values of the JN1 base metal were significantly decreased with increasing the time and temperature of the heat treatment. The fracture toughness value obtained from the fusion line specimen was invalid, but it was lower value than that of the JN1 base metal. Especially, this value was approximately equal with that obtained from the JN1 650.deg. C-5h heat-treated material.