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알루미늄 대상 보빈-마찰교반 용접용 툴 디자인에 관한 리뷰
강상훈(Sanghoon Kang),차종환(Jonghwan Cha),강민정(Minjung Kang) 대한용접·접합학회 2021 대한용접·접합학회지 Vol.39 No.5
Friction stir welding using a bobbin tool (BT-FSW) is a kind of friction stir welding (C-FSW) process in which a lower shoulder is added to the general friction stir welding tool. It is known as the useful method to reduce the Z-axis load required during the tool insertion and traveling for FSW. In addition, it can eliminate the backing plate, and actively respond to part deformation. For this reason, research on the application of BT-FSW is expanding from low melting temperature materials such as aluminum and magnesium to high melting temperature materials. However, no relevant studies on BT-FSW can be found in Korea. This study aimed to present tool design guidelines specifically for BT-FSW. Summarized information on variables to be considered when designing the BT-FSW tool has been described, such as pin and shoulder diameter, shoulder gap, pin and shoulder feature. The design of the tool is a significant step in set-up the BT-FSW process, and should be considered according to the material characteristics (viscosity, plasticity…) and thickness. The pin diameter that is similar to the thickness of material, and the shoulder diameter that is 2 to 3 times wider than the pin diameter were recommended. The shoulder gap, the distance between the upper and lower shoulder, is generally machined to match the material’s thickness or fabricated to be shallower than. Since the pin shape directly affects the vertical and horizontal direction movement into the stir zone, the pins with 3 to 4 flat faces or threaded are more practical than the cylindrical pin shape.
렌즈의 온도 구배를 고려한 결상광학계의 초점 열화 영향 분석
안재훈(Jaehoon Ahn),김은진(Eunjin Kim),차종환(Jonghwan Cha),복기소(Kiso Bok) 대한기계학회 2023 대한기계학회 춘추학술대회 Vol.2023 No.11
In order to address the issue of thermal drift, which causes the focus of the imaging optical system to blur due to temperature changes, an athermal design was conducted. In this process, the influence of temperature gradients distributed across each lens on changes in back focal length (△BFL) was analyzed. As an athermal design approach, the Imaging optical system was functionally divided into a projection system and an image system. The projection system used an optical passive athermalization method, while the image system utilized a mechanical passive athermalization method. Functionally, the projection and image systems were designed so that the movement direction of their respective focal lengths changed in opposite directions, and they were designed to move only a certain distance to ensure that the combined effect after temperature changes would cancel each other out. Additionally, finite element analysis results from multiple physics fields such as optics, optomechanics and cooling field were utilized for a more precise analysis. The proposed athermal design enables the core component, the projection lens, to act as a temperature compensator across the entire system, while reducing tolerance sensitivity, contributing to improvements in optical performance and competitive pricing.