• 소성∙가공
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• 제8권1호
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• pp.7-13
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• 1999

In this study, side panels were developed using the laser-welded tailored blank (T.B.) of both the same thickness and different thickness. At first, the formability of the same thickness T.B. was investigated to compare with one of the non-welded panel with respect to weldline movement and strain distribution in blank during the stamping process. Based on these results, we determined the weld line positions and the die step for T.B. forming of the blanks composed of different thickness combination. Then we made some stamping tryouts with selected types of blanks to investigate the formability of T.B. of the different thickness. During the tryouts, wrinkles were found in the a-pillar lower region which is under the deformation mode of the shrink flange. In the b-pillar region, fractures were also found. These defects have been reduced and corrected by controlling the blank design, the die faces and process parameters.

• 한국전자파학회논문지
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• 제24권12호
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• pp.1120-1127
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• 2013

본 논문에서는 칩온웨이퍼(Chip on Wafer: CoW) 공정기술을 이용한 새로운 칩온칩(Chip on Chip: CoC) 플립칩 범프 구조들을 제안하여 설계, 제작하고, 초고주파 영역에서의 응답 특성을 분석하였다. Cu 필러(Pillar)/SnAg, Cu 필러/Ni/SnAg의 기존 범프들, 그리고 SnAg, Cu 필러/SnAg, Cu 필러/Ni/SnAg를 Polybenzoxazole(PBO)로 보호한 새로운 범프들을 구성하여 웨이퍼의 $2^{nd}$ Polyimide(PI2) 층의 도포 유무에 따라 10가지 형태의 CoC 샘플들을 구조 설계하였고, 20 GHz까지의 주파수 특성이 고찰되었다. 측정 결과를 고려할 때 PI2 층이 도포된 소자들이 본 실험에 사용된 배치 플립칩 공정에 더 적합함을 알 수 있었고, 18 GHz에서 평균 0.14 dB의 삽입 손실을 보였다. 미세 패드 간격을 가지는 칩의 패키지 용도로 새로 개발된 범프들의 삽입 손실(0.11~0.14 dB)은 기존 범프들의 삽입 손실(0.13~0.17 dB)과 비교해 18 GHz까지 유사한 성능을 보이거나, 다소 좋은 특성을 보여 높은 집적도를 요구하는 다양한 초고주파 패키지에 활용될 수 있음이 확인되었다.

• 소성∙가공
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• 제26권2호
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• pp.87-94
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• 2017

Center pillar, which is installed in the center of flank of car body, supports roof and door and ensures the safety of driver by reducing the damage of car body caused by impact. Recently, high-strength steel is widely used to manufacture the center pillar due to high stiffness and fuel efficiency. In this study, material properties of the high-strength steel, whose tensile strength is more than 780MPa, were obtained to produce the center pillar. Stamping was performed by considering the design parameters (blank holder force, press stroke, blank size and pad pressure) used in the actual filed. The drawbeads were included in the stamping process to reduce the amounts of wrinkling and spring back. Using the commercial software, Autoform R5.2 and Minitab, effects of design parameters of the stamping process upon spring back were analyzed and applied to the design process. The restriking process meets the target of under 0.5mm in the amount of spring back.

• 대한기계학회논문집B
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• 제32권11호
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• pp.824-831
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• 2008

We present a continuous size-dependent particle separator using a negative dielectrophoretic (DEP) virtual pillar array. Two major problems in the previous size-dependent particle separators include the particle clogging in the mechanical sieving structures and the fixed range of separable particle sizes. The present particle separator uses the virtual pillar array generated by negative DEP force instead of the mechanical pillar array, thus eliminating the clogging problems. It is also possible to adjust the size of separable particles since the size of virtual pillars is a function of a particle diameter and applied voltage. At an applied voltage of 500 kHz $10\;V_{rms}$ (root mean sqaure voltage) sinusidal wave and a flow rate of $0.40\;{\mu}l\;min^{-1}$, we separate $5.7\;{\mu}m$-, $8.0\;{\mu}m$-, $10.5\;{\mu}m$-, and $11.9\;{\mu}m$-diameter polystyrene (PS) beads with separation purity of 95%, 92%, 50%, and 63%, respectively. The $10.5\;{\mu}m$- and $11.9\;{\mu}m$-diameter PS beads have relatively low separation purity of 50% and 63%. However, at an applied voltage of $8\;V_{rms}$, we separate $11.9\;{\mu}m$-diameter PS beads with separation purity over 99%. Therefore, the present particle separator achieves clog-free size-dependent particle separation, which is capable of size tuning of separable particles.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1998년도 제2회 박판성형심포지엄 논문집 박판성형기술의 현재와 미래
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• pp.102-109
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• 1998

In this study, the side panels were developed using the laser-welded Tailored Blanks (TB) with both the same thickness and the different thickness. At first, the formability of the same thickness T.B was investigated to be compared with one of the non welded panel with respect to weldline movements and strain distribution on blank during the stamping. Based on these results, we selected candidates of T.B with different thickness for stamping experiments. That is, we determined the weld line positions and the die step. Then we made some stamping tryouts with selected types of blank designs to investigate the formability of T.B with different thickness. During the tryouts, the wrinkles were found in the a-pillar lower region which is under the deformation mode of the shrink flange. In the b-pillar region, the fractures were found also, these defects have been reduced and corrected by controlling the blank design and the die faces and process pamameters.

• 소성∙가공
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• 제23권5호
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• pp.297-302
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• 2014

The current paper introduces work that was conducted during the development of a stamping die for a reinforce center pillar made from high strength steel. In the current study, the Bauschinger effect on the springback analysis was studied by comparing simulation results with real panels, which are currently in production. For a complicated part shape, quantitative measurements of the deformed shape are not easy in general to obtain. An adjustment procedure of the shape data for some chosen sections has been suggested to improve the accuracy of the quantitative measurements. The results show that the kinematic hardening model provides more accurate results.

• 환경영향평가
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• 제14권4호
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• pp.179-193
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• 2005

As the world's attention turns to sustainability and the considerations of cumulative effects, the concept of Strategic Environmental Assessment(SEA) has become more significant and urgent and increasing number of countries and international organizations now undertake some forms of SEA. The term SEA, however, is variously defined and understood; generally it means a formal process of systematic analysis of the environmental effects on development policies, plans, programmes and other proposed strategic actions. This process extends the aims and principles of EIA upstream in the decision-making process, beyond the project level in which major alternatives are still open. There is a shift toward more integrative approaches and greater use of Environmental Impact Assessment (EIA) and Strategic Environmental Assessment (SEA) as sustainability tools in cooperation with Environmental Management System (EMS). Currently, Korea has EIA system and Prior Environmental Review System (PERS) which is different type of SEA as Environment Assessment (EA) system. APEMI IA MODEL integrated following three pillar(refer to attached figure.1) ; First pillar symbolized decision making cycle with planning process. Second pillar symbolized integrated assessment which tying SEA and EIA with specific impacts assessment(eg: social impact assessment, economic impact assessment, health impact assessment etc) in cooperation with EMS. Third pillar symbolized EA best practical procedure of International Association for Impact Assessment(IAIA). Considering the above, we applied new conceptual model(APEMI IA MODEL) into Impact Assessment for better integrated decision-making in KOREA as an alternative IA system(IS IA MODEL A and B refer to attached figure 4, 5).

• 대한기계학회논문집B
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• 제24권10호
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• pp.1309-1316
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• 2000

A surface flow visualization of a MIRA notchback reference car was conducted using a 1/4 -scale model in the POSTECH wind tunnel. The flow separation and reattachment phenomen a around A-pillar, C-pillar, backlight, and trunk were discussed with the help of the distributions of singular points such as nodes, saddles, and spiral foci. The locations of the singular points on the trunk and the backlight from experimental results are compared with those of CFD results using the turbulence modeling of RNG k -${\varepsilon}$ and RSM.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.473-474
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• 2012

• 열처리공학회지
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• 제23권6호
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• pp.301-308
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• 2010

A steel with chemical composition, 0.22% C, 0.25% Si, 1.26% Mn, 0.22% Cr, 0.04% Ti, 0.0042% B, and a microstructure of ferrite and spheroidized cementite has been press-formed to automotive center pillar followed by local-hardening heat-treatment. Hardness, tensile properties, fractography, microstructure and surface roughness of local-hardening heat-treated automotive center pillar have been examined. The directly heated and quenched area had fully martensitic structure with Vickers hardenss in the range of 500 to 510. The heat affected area close to the directly heated area showed dual-phase structure of ferrite and martensite. The width of the heat-treated and heat-affected areas after the local-hardening heat treatment was ranging from 32 mm to 50 mm. The surface of the local-hardening heat-treated center pillar revealed some temper color as a consequence of the oxidation during the heat treatment, but the surface roughness was not affected by the local-hardening heat treatment.