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박홍선(Hong-Sun Park),김정은(Chong-Eun Kim),문건우(Gun-Woo Moon) 전력전자학회 2006 전력전자학술대회 논문집 Vol.- No.-
a current stress reduction technique for a boost integrated half-bridge (BIHB) DC/DC converter with voltage doubler type rectifier is proposed for digital car audio amplifier application. In the proposed circuit, two external capacitors are added parallel to the rectifier diodes in the secondary side of the transformer to shape the primary and the secondary current like rectangular waveforms in every switching instance. The experimental results of a 200W industrial sample show that the peak primary current decreases about by 10A. Thus, the proposed technique shows improved high efficiency.
피로 손상 모델을 이용한 직조 탄소섬유강화 복합재료의 피로 손상 평가
박홍선(Hong Sun Park),최정훈(Jung Hun Choi),구재민(Jae Mean Koo),석창성(Chang Sung Seok) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.6
탄소섬유강화 복합재료는 금속재료에 비하여 높은 비강성과 비강도 등의 우수한 기계적 성질을 나타내고 있으며, 이러한 이유로 최근 경량화가 요구되는 항공기용 재료와 자동차용 재료 등으로 그 사용이 급격히 증가하여 금속재를 대체하고 있다. 그러나 대부분의 기계구조물에서는 반복하중에 의한 피로 파손이 주로 발생하고 있다. 그러므로 섬유강화 복합재를 사용한 기계구조물의 내구성을 확보하기 위해서는 이에 대한 피로해석 및 내구성 평가가 필요하다. 따라서 피로 손상 모델을 이용하여 피로 시험으로부터 구한 손상량을 이용하여 피로손상 누적곡선을 획득하고 해석하였다. Owing to the high specific strength and stiffness of composite materials, they are extensively used in mechanical systems and in vehicle industries. However, most mechanical structures experience repeated load and fatigue. Therefore, it is important to perform fatigue analysis of fiber-reinforced composites. The properties of composite laminates vary depending upon the stacking sequence and stacking direction. Fatigue damage of composite laminates occurs according to the following sequence: matrix cracking, delamination, and fiber breakage. In this study, fatigue tests were performed for damage analysis. Fatigue damages, which have to be considered in fatigue analysis, are determined by using the stiffness values calculated from hysteresis loops, and the obtained fatigue damage curve is examined using Mao's equation and Abdelal's equation.
박홍선(Hong Sun Park),최정훈(Jung Hun Choi),강민성(Min Sung Kang),구재민(Jae Mean Koo),석창성(Chang Sung Seok) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.4
탄소섬유 강화 복합재료는 높은 비강도와 비강성을 지니고 있어 여러 산업 분야에서 그 사용이 증가하고 있다. 복합재료는 여러겹으로 적층하여 제작하기 때문에 두께 방향으로의 강도가 부족하고, 외부 물체의 충돌에 의한 충격 손상에 매우 취약하다. 따라서 재료의 건전성 및 신뢰성을 확보하기 위해서는 충격 손상 후의 재료 거동 및 하중지지능력에 대한 평가 및 해석이 필요하다. 따라서 본 논문에서는 자유 낙하 충격 시험을 통해 탄소섬유강화 복합재료에 충격 손상을 가하고 그에 대한 충격 후 잔류 강도 시험을 통해 충격에너지에 따른 재료의 거동에 대해서 평가하고, 섬유배열 방향에 따른 충격 후 잔류 강도 거동을 평가함으로써 임의의 각도를 갖는 시편에 대한 잔류 강도를 예측 및 평가하고자 한다. Composite materials have a higher specific strength and modulus than traditional metallic materials. The uses of composite materials increase in various industries. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. Impact test was performed using drop weight impact tester. And residual strength behavior by impact was evaluated. Also we evaluated and predicted the residual strength in according to the fiber-arrayed angle.
피로 손상 모델을 이용한 직조 탄소섬유강화 복합재료의 피로 손상 평가
박홍선(Hong Sun Park),최정훈(Jung Hun Choi),구재민(Jae Mean Koo),석창성(Chang Sung Seok) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11
Composite materials are extensively used in mechanical system and vehicular industries due to the high specific strength and stiffness. However, most mechanical structures experience the repeated load and fatigue. Therefore it is important to perform the fatigue analysis of fiber-reinforced composites. Considered on the various stacking sequence and direction, the properties of composite laminates vary. Fatigue damage process of composite laminates follows this sequence such as the matrix cracking, delamination and fiber breakage. This study performed the damage analysis through fatigue test. Fatigue damages which needed to fatigue analysis are obtained using stiffness calculated from hysteresis loop and fatigue damage curve is examined through the proposed models such as Mao's equation and Abdelal's equation.
에틸렌옥사이드기를 포함하는 폴리스티렌 유도체의 합성과 이온전도특성
박홍선(Hong-Sun Park),류상욱(Sang-Woog Ryu) 한국고분자학회 2018 폴리머 Vol.42 No.1
본 연구에서는 에틸렌옥사이드기를 가지는 스티렌 유도체(PEGMS)를 마크로모노머로 합성하였으며, 라디칼 중합을 통하여 단량체 단위당 곁사슬이 정량적으로 도입된 그래프트 공중합체를 제조하였다. 고분자전해질에 대한 전기화학 측정결과, 마크로모노머의 분자량이 클수록 높은 이온전도도가 나타났다. 또한 같은 PEGMS의 분자량에서도 이온전도도는 리튬염의 농도에 따라 변화하였다. 특히 [EO]:[Li] 비율 30:1에서 기질이 결정성에서 무정형으로 전환되었으며 최대 5.11×10<SUP>-5</SUP> S/cm의 이온전도도가 관찰되었다. 하지만, 더 높은 리튬이온 농도는 기질의 유리전이 온도를 증가시켰고, 반대로 더 낮은 리튬이온 농도는 기질의 결정성을 억제하지 못하였다. 따라서 높은 이온전도도를 확보하기 위해서 첨가되는 리튬염의 양은 기질의 결정성을 억제하는 수준으로 조절해야 한다. In this study, styrene derivative having ethylene oxide group (PEGMS) was synthesized as a macromonomer, and graft copolymer in which side chains were quantitatively introduced into each monomer unit was prepared by radical polymerization. From the electrochemical measurement of polymer electrolytes, it was found that the higher the molecular weight of macromonomer, the higher the ionic conductivity. Also, the ionic conductivity of the same PEGMS varied with the concentration of lithium salt. In particular, the polymer substrate was converted from crystalline to amorphous at [EO]:[Li] ratio of 30:1 and ion conductivity of up to 5.11 × 10<SUP>-5 </SUP>S/cm was observed. However, the higher lithium ion concentration increased the glass transition temperature of the substrate, while the lower lithium ion concentration did not suppress the crystallinity of the substrate. Therefore, the amount of lithium salt for a high ionic conductivity should be adjusted to a level that inhibits the crystallinity of the polymer substrate.
박홍선(Hong-Sun Park),허용,구재민(Jae-Mean Koo),석창성(Chang-Sung Seok),박재실(Jae-Sil Park),Sung-Keun Cho 대한기계학회 2009 大韓機械學會論文集A Vol.33 No.9
The estimation method of the fracture resistance curve for the pipe specimen was proposed using the load ratio method for the standard specimen. For this, the calculation method of the load - CMOD curve for the pipe specimen with the common format equation(CFE) was proposed by using data of the CT specimen. The proposed method agreed well with experimental data. The J-integral value and the crack extension were calculated from the estimated load - CMOD data. The fracture resistance curve was estimated from the calculated J-integral and the crack extension. From these results, it have been seen that the proposed method is reliable to estimate the J-R curve of the pipe specimen.