• Transactions of Materials Processing
• /
• v.13 no.2
• /
• pp.122-128
• /
• 2004

In order to make a doubly-curved sheet metal effectively, a sheet metal forming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation in thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the direction of one principal radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principal radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It mainly affects the generation of curvature in its own direction with the forming depth and the thickness of the material.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2005.10a
• /
• pp.322-325
• /
• 2005

In order to make a doubly-cowed sheet metal effectively, the sheet metal forming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation in thickness. The developed process is an unconstrained forming process without holder. The experimental equipment has been set up with the roll set which consists of two pairs of support rolls and one center roll. In order to analyze process parameters in the incremental roll forming process for the application to doubly curved ship hull plate, the orthogonal array is adopted. From the FEM results, among the process parameters, the distance between supporting rolls in pairs along the direction of one principal radius of curvature as well as the forming depth is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principal radius of curvature, does not have an significant effect on the generation of the curvature in that direction. Also, the forming load and torque from the FEM simulation are acceptable to the system development of the incremental roll forming process for the forming of ship hull plate.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2003.08a
• /
• pp.53-57
• /
• 2003

In order to make a doubly curved sheet metal effectively, a sheet metal farming process has been developed by adopting the flexibility of the incremental forming process and the principle of bending deformation which causes slight deformation to thickness. The developed process is an unconstrained forming process with no holder. For this study, the experimental equipment is set up with the roll set which consists of two pairs of support rolls and one center roll. In the experiments using aluminum sheets, it is found that the curvature of the formed sheet metal is determined by controlling the distance between supporting rolls in pairs and the forming depth of the center roll and it also depends on the thickness of the sheet metal. In order to check the effect of process parameters on the generation of sheet metal curvatures in this process, the orthogonal array is adopted. From the experimental results, among the process parameters, the distance between supporting rolls in pairs along the same direction of one principle radius of curvature as well as the forming depth and the thickness of the material is shown to influence the generation of curvature in the same direction significantly. That is, the other distance between supporting rolls in pairs which are not located in the same direction of one principle radius of curvature, does not have an significant effect on the generation of the curvature in that direction. It just affects the generation of curvature in its own direction mainly with the forming depth and the thickness of the material.

• Polymer(Korea)
• /
• v.28 no.3
• /
• pp.232-238
• /
• 2004

MPEG-PCL diblock copolymers consisting of methoxy poly(ethylene glycol) (MPEG) and $\varepsilon$-caprolactone (CL) as drug carriers were synthesized by ring-opening polymerization MPEG-PCL diblock copolymers were characterized by X-ray diffraction and differential scanning calorimetry. After freeze milling of block copolymers and albumin bovine-fluorescein isothiocyanate (FITC-BSA) as model protein, the wafers loaded FITC-BSA were fabricated by direct compression method. The release profiles of FITC-BSA were examined using pH 7.4 PBS for 14 days at 37$^{\circ}C$. The release amount was determined by fluorescence intensity by using the fluorescence spectrophotometer. The morphological change of wafers was observed by digital camera and scanning electron microscope. The release rate and initial burst of BSA increased with increasing PEG molecular weights and decreasing PCL molecular weights in the segments of MPEG -PCL diblock copolymers.

• Korean Journal of Metals and Materials
• /
• v.47 no.8
• /
• pp.494-499
• /
• 2009

As a novel method to produce a steel beam with 6mm thickness for buildings, a continuous roll forming process is reported. The roll shape is asymmetric and consists of 6 pairs of rollers to bend the steel plate from $0^{\circ}$ to $90^{\circ}$. Results obtained upon application of the roll forming process showed that the angle of the section plate is $90^{\circ}$. However, defects such as bowing and camber as high as 3.2 [$^{\circ}/m$] were observed. A FEM (Finite Element Method) analysis was applied to investigate the causes of the results for the region between rollers no. 5 and no. 6. The results of a FEM simulation of deformation and stress showed that there are some strong peak stresses on the upper surface and bottom surface of the material. The positions of the peak stresses did not show a correspondence between the upper and bottom surfaces. Thus, the defects in the process of roll forming with a 6 mm thick steel plate occur by the unbalanced stresses between the upper surface and bottom surface of the material in this study.

• Design & Manufacturing
• /
• v.17 no.3
• /
• pp.15-20
• /
• 2023

In the fine blanking process, which is a press operation known for producing parts with narrow clearances and high precision through the application of high pressure, die roll often occurs during the shearing process when the punch penetrates the material. This die roll phenomenon can significantly reduce the functional surface of the parts, leading to decreased product performance, strength, and fatigue life. In this research, we conducted an in-depth analysis of the factors influencing die roll in the curvature area of the fine blanking process and identified its root causes. Subsequently, we designed and experimentally verified a die roll reduction process specifically tailored for the door latch manufacturing process. Our findings indicate that die roll tends to increase as the curvature radius decreases, primarily due to the heightened bending moment resulting from reduced shape width-length. Additionally, die roll is triggered by the absorption of initial punch energy by scrap material during the early shearing phase, resulting in lower speed compared to the product area. To mitigate the occurrence of die roll, we strategically selected the Shaving process and carefully determined the shaving direction and clearance area length. Our experiments demonstrated a promising trend of up to 75% reduction in die roll when applying the Shaving process in the opposite direction of pre-cutting, with the minimum die roll observed at a clearance area length of 0.2 mm. Furthermore, we successfully implemented this approach in the production of door latch products, confirming a significant reduction in die roll. This research contributes valuable insights and practical solutions for addressing die roll issues in fine blanking processes.

• Journal of Korean Society of Steel Construction
• /
• v.16 no.1 s.68
• /
• pp.33-42
• /
• 2004

Making use of SN steel in the building structure should be a prerequisite to adopt the design strength of said steel. As a preceding study, the material properties of STKN400B/490B tubes and SPAP235/325 and SPAR295 square pipes manufactured using SN400B/490B plates were evaluated. Compared with the yield and ultimate strengths of SN400B/490B plates, those of STKN400B/490B tubes increase. Nonetheless, the yield and ultimate strengths of STKN400B/490B tubes satisfied the design codes of STKN400B/490B tubes even though the tubes were fabricated via roll bending or press forming. On the other hand, the yield and ultimate strengths at the edges of SPAP235/325 square pipes did not satisfy the design codes based on the values at the sides. The maximum tensile and compressive residual stresses at the SN490B tube were equal to and 40% of the yield strength of the SN490B plate, respectively, In the case of the SPAP325 square pipe, both the maximum tensile and compressive residual stresses were 80% of the yield strength of the SN490B plate. The axial compressive loaded column test results snowed that the buckling strengths were not very different regardless of the mode of fabrication of STKN490B tunes. i.e., through roll bending or press forming. On the other hand, the buckling strength of the SPAP325 square pipe was higher than that of the built-up square pipe.

• Proceedings of the Korean Society for Agricultural Machinery Conference
• /
• 2002.02a
• /
• pp.282-288
• /
• 2002

본 연구는 상업용 규모의 쇄미선별공정에 사용할 수 있는 파이로트 규모 원통형 홈 선별기 시작기의 설계 및 제작에 필요한 기초 연구로서, 실험실용 원통형 홈 선별기를 이용하여 쇄미선별 실험을 실시하였다. 원통 회전속도, trough각도, indent 크기와 형상, 공급량을 요인으로 하여 완전립의 수거율과 순도, 쇄립의 수거율과 순도 및 선별효율을 조사하였다. 수행한 연구결과를 요약하면 다음과 같다. 1. 선별효율에 대한 원통 회전속도와 trough각도의 단독효과 및 교호작용은 1% 수준에서 유의성이 인정되었다. 원통 회전속도가 커지면trough각도 역시 그에 따라 적절히 증가시켜야만 선별효율의 저하가 방지되는 것으로 나타났다. 2. 최고 선별효율 값은 홈의 모양과 크기, 그리고 공급량에 관계없이 낮은 회전속도 (17rpm)와 중간 trough각도 (37.5$^{\circ}$또는 60$^{\circ}$)가 조합된 처리에서 나타났으며, 60~70% 범위의 높은 값을 보였다. 선별효율에 관한 원통 회전속도와 trough각도의 최적 조합은 17rpm, 37.5$^{\circ}$라고 판단된다. 3. 말발굽형 홈과 반구형 홈 간 선별효율의 차이는 없었다. 따라서, 실제 상업용 규모의 원통형 홈 쇄미선별기 개발에 있어서는 제작이 쉽고 유지.보수가 간편한 반구형 홈을 채택하는 것이 바람직할 것으로 생각된다. 길이 2.5mm이하의 미립인 쇄미의 선별에 사용할 홈의 크기는 2.5mm 보다는 약간 큰 3.0mm 정도가 되어야만 할 것으로 판단된다. 4. 공급량에 따른 선별효율의 차이는 1% 수준에서 유의성이 인정되었으며, 공급량이 작았을 때 전반적으로 선별효율이 높았다.타리 시프터를 채택, 사용하고 있었으며, 로타리시프터 사용상의 문제는 회전몸체를 지지하는 rod spring의 파손 등 구조와 관련된 것이었다. 로타리 시프터에 의한 쇄립의 선별과 제거정도는 만족할 만한 수준은 아니었다. 4. 국내 유통백미 완전립의 길이, 폭, 두께는 각각 5.02mm, 2.93mm, 2.03mm이었으며, 산물밀도와 천립중은 각각 745.3kg/m3 및 20.46g이었다. 5. RPC 백미제품의 품질경쟁력 향상을 유도하고자 현행 쇄미의 정의와 기준을 보다 강화하여 다음과 같은 쇄미 기준과 계급을 설정, 제시하였다. "완전립" - 길이가 3.75mm이상인 미립 "준완전립" - 길이가 2.5∼3.75mm인 미립 "쇄미" - 길이가 1.75∼2.5 mm인 미립 "이물" - 길이가 1.75mm이하인 미립.볼 때 상토 종자혼합비 6 : 1, 성형롤 회전속도 약 7 rpm으로 판단되며, 이 때 제조능력은 시간당 약 65 Kg(펠렛종자 약 39,000 개), 성형률 약 87 %, 종자손실률은 약 30 %, 펠렛종자 내 평균 종자수는 약 5.5 개, 완전 벼 종자 3개 이상 포함 펠렛종자 비율은 약 100 %가 될 것으로 보인다. 세포의 Androgen 생성을 촉진시키는 역할이 있는 것으로 보여진다 따라서 옻나무 유래 F는 포유동물의 생식기능에 중요하게 작용하는 것으로 사료된다.된다.정량 분석한 결과이다. 시편의 조성은 33.6 at% U, 66.4 at% O의 결과를 얻었다. 산화물 핵연료의 표면 관찰 및 정량 분석 시험시 시편 표면을 전도성 물질로 증착시키지 않고, Silver Paint 에 시편을 접착하는 방법으로도 만족한 시험 결과를 얻을 수 있었다.째, 회복기 중에 일어나는 입자들의 유입은 자기폭풍의 지속시간

• Clean Technology
• /
• v.23 no.2
• /
• pp.133-139
• /
• 2017

Bio-based plastics containing the biomass content higher than 25 wt% have been considered as environment-friendly materials due to their effects on the reduction in the $CO_2$ emission and petroleum consumption as well as biodegradability after use. In this study, poly vinyl chloride, plant-derived plasticizers, by adding a biodegradable catalyst was observed a change in the biodegradability and physical properties. To produce the oxidative decomposition transparent bio film, which is broken down in the initial percent elongation and physical properties such as tensile strength, it was to test the safety of the product as a food packaging material. Poly vinyl chloride, primary plasticizer, secondary plasticizer, anti fogging agent, the combined stabilizer were mixed in a high speed mixer, then extruded using an extrusion molding machine, after cooling, winding, to produce a oxidative decomposition transparent bio film and the control film, with a thickness of $12{\mu}m$ through winder role. Mechanical properties tensile strength, elongation, and the maximum load elongation and biodegradation test. Transparent bio film produced by biodegradation catalyst is compared with the control film. Tensile strength and elongation of films were found to be no significant difference. Further, as a result of the biodegradation test for 45 days based on the ASTM D6954-04 method, biodegrability of film is 61.4%.