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Incremental Forming of 3D Structured Aluminum Sheet
Van-Cuong Do,Duc-Toan Nguyen,조준행,김영석 한국정밀공학회 2016 International Journal of Precision Engineering and Vol.17 No.2
In this paper we investigated the deformation characteristic of embossed aluminum sheet in the incremental sheet forming process which has frequently used in the design verification and the trial manufacturing of sheet products. The single point incremental forming (SPIF) experiments for the rectangular cone forming using the CNC machine with a chemical wood-machined die and a circular tool shape showed that the formability of the embossed sheet are better than that of the flat sheet in view of the maximum angle of cone forming. This comes from the fact that the embossed sheet between the tool and the elastic die wall is plastically compressed and the flatted area contributes to increase the plastic deformation. Also the tool path along the outward movement from the center showed a better formability than that of the inward movement from the edge. However the surface quality for the tool path along the outward movement evaluated from the surface deflection is inferior than that of the tool path along the inward movement. The experimental results and detail forming mechanism of the 3D structured sheet in incremental forming were reviewed with a finite element simulation using ABAQUS software.
Formability and Effect of Hole Bridge in the Single Point Incremental Forming
Van-Cuong Do,샤오 샤오,안대철,김영석 한국정밀공학회 2017 International Journal of Precision Engineering and Vol.18 No.3
This paper studies the mechanical properties, formability and effect of hole bridge (hole lancing) in the single point incremental forming for Al5052-O with the thickness of 0.8 mm. The mechanical properties, including anisotropy property and stress-strain relation, were evaluated by uniaxial tensile tests in three directions of 0°, 45°, 90° with the rolling direction. Varying wall angle conical frustum test was used to study the formability. The forming parameters of tool diameter, step depth, spin speed, and feed rate were optimized using multi-objective optimization with grey relational grade. The results show that the tool diameter strongly influences formability, springback and thickness reduction. To verify the effect of hole bridge on the formability, a predesigned hole bridge was machined by a laser on the blank shoulder nearby the forming periphery before forming. The optimized forming parameters found in previous step were applied for this test. As the result, the maximum forming angle was significantly improved in comparison with the non-hole-bridge part. Finite element simulation by ABAQUS explicit software was used to explain the strain evolution in the blank with cut-off hole of the incremental forming process. The simulation results were compared with experiment and discussed.
3D 구조 알루미늄 판재의 점진판재성형 특성 평가 (제2보)
김영석(Kim, Young-Suk),Van-Cuong Do,안대철(Do, Van-Cuong) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.3
3차원 구조 알루미늄 판재(엠보싱 판재)는 표면적이 증가되어 방열효과가 뛰어나고 가공경화에 의해 굽힘강성 증가 효과가 있으므로 자동차 열차단 부품에 널리 사용된다. 그러나 엠보싱 판재는 평판의 판재와 비교하면 기계적 특성이 상이하 고 또한 3차원 형상으로 인해 프레스 가공에 있어서 많은 제약이 따른다. 본 연구에서는 프레스 가공공정을 대신하여 최근 신제품의 디자인 검증과 시생산에 널리 채용되고 있는 점진성형공정을 대상으로 엠보싱된 판재의 성형특성을 평가하였다. 본 연구에서 채용한 공구형상을 이용한 사각 원뿔의 점진성형 결과, 엠보싱된 판재의 경우가 평판의 경우보다 더 큰 기울기를 갖는 사각 원뿔을 파단없이 성형할 수 있음을 보였다. 이는 점진성형공정에서 CNC 공구의 이동경로(tool path)하에서 공구가 엠보싱 판재의 산과 골을 눌러 복원시키면서 재료의 소성변형을 증가시키기 때문이다. 또한 공구의 이동경로가 내향 경로보 다 외향 경로인 경우가 보다 큰 기울기의 제품을 성형할 수 있지만 스프링 백의 발생으로 제품의 표면품질은 열세에 있음을 보였다. 3D-structured (embossed) aluminum sheets have been used in the heat insulation purpose for automative exhaust parts because of increasing their surface areas and stiffness reinforcement imposed in making the embossing pattern. However, there are many restrictions in press forming of the embossed sheet compared with the flat sheet (non-embossed one) because of its difference in the mechanical properties and the geometrical 3-dimensional shape. In this paper we investigated the deformation characteristic of embossed aluminum sheet in the incremental sheet forming process which has frequently used in the design verification and the trial manufacturing of sheet products. The single point incremental forming (SPIF) experiments for the rectangular cone forming using the CNC machine with a chemical wood-machined die and a circular tool shape showed that the formability of the embossed sheet are better than that of the flat sheet in view of the maximum angle of cone forming. This comes from the fact that the embossed sheet between the tool and the elastic die wall is plastically compressed and the flatted area contributes to increase the plastic deformation. Also the tool path along the outward movement from the center showed a better formability than that of the inward movement from the edge. However the surface quality for the tool path along the outward movement evaluated from the surface deflection is inferior than that of the tool path along the inward movement
엠보싱 알루미늄 판재의 기계적특성과 스프링백 평가 (제1보)
김영석(Kim, Young-Suk),조준행(Cho, Jun-Haeng),Van-Cuong Do,신동우(Do, Van-Cuong) 한국산학기술학회 2015 한국산학기술학회논문지 Vol.16 No.2
엠보싱된 알루미늄 판재는 표면적이 증가하여 방열효과가 뛰어나고 가공경화에 의해 굽힘강성이 증가하여 자동차 열차단기에 널리 사용된다. 하지만 판재의 특성상 주름발생률이 높아 프레스 성형에 많은 제약이 따른다. 본 연구에서는 3차원 구조 알루미늄 판재의 프레스 성형성 평가를 위한 기초연구로 3차원 구조 엠보싱 콘 형상 판재의 기계적특성을 평가 하고 굽힘실험을 통해 프레스 가공 후 발생하는 스프링백을 정량적으로 평가하였다. 엠보싱 판재는 패턴의 방향에 따라 인장특성이 상이하다. 특히 평행 엠보싱 시편의 경우 항복응력이 감소하며 대각 엠보싱 시편의 경우 항복응력이 증가하게 되고 영률의 감소가 크게 나타난다. 그 결과 굽힘 성형가공 후에 스프링 백에 영향을 미친다. Embossed aluminum sheets were been used in heat insulation purpose for automative exhaust parts because of increasing their surface areas and stiffness reinforcement. However, there are many restrictions because of high rate of wrinkle occurrence on press working. We have performed the tensile and bending tests for embossed sheets to clarity its mechanical properties and springback characteristics. Embossed aluminum sheets showed a different flow stress after plastic yielding due to flattening the embossed cone shape. Above all, yield stress of parallel embossed specimen decreases while its diagonal one increases and the decrease of young’s modulus in the embossed sheets contributes to the increase of springback amount.
New Alkaloids and Anti-inflammatory Constituents from the Leaves of Antidesma ghaesembilla
Van Kiem, Phan,Cuong, Le Canh Viet,Trang, Do Thi,Nhiem, Nguyen Xuan,Le Tuan Anh, Hoang,Tai, Bui Huu,Huong, Le Mai,Van Minh, Chau,Lee, Taek Hwan,Kim, Sun Yeou NATURAL PRODUCT COMMUNICATIONS 2017 Natural product communications Vol.12 No.1
Van Cuong, Phan,Kim, Do-Hyung Institute of Physics 2009 Journal of Physics: Conference Series Vol.187 No.1
<P>La<SUB>1-x</SUB>Sr<SUB>x</SUB>MnO<SUB>3</SUB> (x &equal; 0.1, 0.2, and 0.3) nanoparticles (LSMO NPs) were successfully synthesized by a simple sonochemical-assisted method. The prepared samples were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The compositions of samples were determined by energy-dispersive spectroscopy (EDS) analysis. The temperature dependence of the resistivity of samples was measured using four-probe technique, and the magnetic measurement was performed in a Magnetic Property Measurement System (MPMS XL 7.0). SEM, TEM, and XRD show that LSMO NPs are 40∼80 nm in diameter with a very clean surface, and exhibit single phase perovskite structure. The ferromagnetic transition temperature (T<SUB>c</SUB>) and metal-insulator transition temperature (T<SUB>p</SUB>) of the NPs increase with the doping level x. The maximum values of T<SUB>c</SUB> (377 K) and T<SUB>p</SUB> (264 K) occur at x &equal; 0.3. In this work, the effect of strontium doping level on electrical transport and magnetic properties was systematically studied.</P>