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남기우(K. W. Nam),황석환(S. H. Hwang),김대용(D. Y. Kim),이문용(M. Y. Lee),이상문(S. M. Lee) 대한기계학회 2012 大韓機械學會論文集A Vol.36 No.10
핫 스탬핑은 오스테나이트 변태 온도 이상에서 프레스 성형 후 급속히 냉각되는 고강도 부품을 제조하는 성형 방법이다. 매우 적은 양의 보론 성분을 가지고 있는 보론강은 핫 스탬핑에 사용되는 재료 중의 하나이다. 본 연구의 목적은 열처리 조건에 따르는 기계적 성질과 에릭슨 커핑 시험에 의하여 성형성을 조사하는 것이다. 다양한 온도에서 다이퀜칭은 대기 시간을 달리하여 실시하였다. 1173 K-0s에서 퀜칭 후 TWB는 1203 MPa의 인장 강도를 얻었다. 이것은 모재 인장강도(1,522 MPA)의 79 %이다. 금형 온도(298, 523, 673 K)에 따른 보론강 TWB의 성형성은 차이가 크지 않았다. 그러나 성형 속도가 증가함에 따라 성형성이 감소하는 것을 확인할 수 있었다. The hot-stamping technique is a forming method used for manufacturing high-strength parts, in which a part is cooled rapidly after press forming above the austenite transformation temperature. Boron steel, which contains a very small amount of boron, is one of the materials used for hot stamping. The purpose of this study is to investigate the mechanical properties of boron steel according to the heat-treatment conditions and the formability by using an Erichsen cupping test. Die quenching from various temperatures was conducted for different elapsed heat-treatment times. Laser-welded boron steel after quenching at 1173 K-0 s has a tensile strength of 1203 MPa. This is 79% of the tensile strength of the base metal (1522 MPa). The formability of boron steel was not significantly different from that at the mold temperature. However, it decreased with increasing forming speed. These properties provide practical information for the use of boron steels for hot stamping.
최현준(H. J. Choi),이상문(S. M. Lee),남문희(M. H. Nam),이영호(Y. H. Lee) 한국동력기계공학회 2009 한국동력기계공학회 학술대회 논문집 Vol.2009 No.11
The current study looks at the flow characteristics in a burner model using PIV. PIV(Particle Image Velocimetry) measurements is an optical method of fluid visualization. It is used to provide qualitative understanding about the spatial distribution and quantitative information about flow. The combustor currently studied had two sets of inlets, first inlet and second inlet. First inlet had 6 holes while two different second inlet configuration was studied, 10 hole and 15 hole. Aluminum powder was used as the seeded particle and the flow rate was kept constant at 40L/min. The first inlet was moved in increments towards the second inlet to see how the flow modifies and obtain the best position and the best second inlet configuration. Information regarding the flow field such as average velocity is presented for both the models in this paper.
내관 자침 시 염전 횟수가 심박 변이도에 미치는 영향: 예비연구
이봉효 ( Bong Hyo Lee ),정재환 ( Jae Hwan Chung ),손지국 ( Ji Gook Son ),허정현 ( Jeong Hyeon Heo ),박지하 ( Ji Ha Park ),김희영 ( Hee Young Kim ),이상남 ( Sang Nam Lee ),이영준 ( Young Joon Lee ),김미려 ( Mi Ryeo Kim ),임성철 ( S 경락경혈학회 2013 Korean Journal of Acupuncture Vol.30 No.2
Objectives: In the acupuncture treatment of Korean Medicine, the Tonifying or Purging depending on how many times the needle is rotated has been used widely. However, there is little evidence about the optimal number of rotation. This study, therefore, was aimed to investigate the optimal number of rotation. Methods: Heart rate variation was measured before and after exercise in 20 healthy adults. Acupuncture was performed at PC6 immediately after exercise according to the protocol of each group without remaining. Pre-exercise and post-exercise measurements were compared and the rotation number that produced statistically significant difference was investigated. Results: Significant differences were found in the heart rate variation and R-R interval Average, between non-rotation group (control) and both of 15 times rotation group of tonifying and 6 times rotation group of purging. Conclusions: Significantly effective number of rotation in the effect of PC6 on the HR and RRAv was 15 times in the tonifying and 6 in the purging respectively.
탄소섬유복합재료의 충격 손상에 따른 파괴 인성과 AE 특성
오세규,남기우,이상국 韓國非破壞檢査學會 1997 한국비파괴검사학회지 Vol.17 No.2
탄소섬유강화복합재료(CFRP)적층판에 비교적 낮은 에너지의 충격을 주어, 충격에 의해서 손상된 적충판을 사용하여 인장강도, 파괴 인성 및 AE 신호에 미치는 충격손상의 영향에 대하여 검토하였다. 충격손상재의 인장강도, 파괴 인성 및 AE-event count는 충격 속도와 박리 면적의 증가에 따라서 감소함을 알 수 있었다. 그리고 충격시험시에 발생한 박리 면적은 충격 속도와 비례하였다. 또한 적층 방법에 따른 손상재의 강도비와 파괴 인성비가 달라짐이 확인되어 복합재료의 내충격 설계시 손상량과 손상재의 파괴 인성 및 강도에 대한 정량적 평가를 AE 신호로부터 해석할 수 있음이 확인되었다. Impact behavior of carbon fiber reinforced plastic (CFRP) laminates were evaluated with tesion test and compact tension test. A steel ball launched by an air gun collides against CFRP laminates to generate impact damage of relatively low energy. The static tensile and fracture toughness tests were performed to evaluate the residual strength and the AE behavior of impact-damaged laminates. As a results, it was found that the static strength, the fracture toughness and the AE-event count were decreased with increasing of impact velocity and delamination area, and to have a different strength ratio and fracture toughness ratio for each stacking method. And also,it was confirmed that strength and fracture toughness of impact-damaged CFRP laminates could be evaluated and analyzed quantiatively by AE techniques.