실 사이드의 열간 프레스 성형을 위한 트림리스 블랭크 설계

이인규(In-Kyu Lee),이성윤(Sung-Yun Lee),이상곤(Sang-Kon Lee),안민수(Min-Su Ahn) 한국기계가공학회 2016 한국기계가공학회지 Vol.15 No.5

The trimming process is required for satisfying the dimensions of a final product in the hot stamping process. In general, the mechanical trimming or laser trimming process is applied after hot stamping. However, these processes have several disadvantages such as short tool life and low productivity. Therefore, in this study, the optimal trimless blank shape for the hot stamping process of a sill side was designed to remove the trimming process after hot stamping. In order to design the trimless blank, numerical analysis was performed. Firstly, CFD analysis was carried out to predict the cooling temperature and holding time of the hot stamping process. Then, the optimal trimless blank shape was determined through FE analysis. The effectiveness of the designed trimless blank shape was verified through a hot stamping experiment at an actual industrial site.

Optimization of Initial Blank Shape for Minimizing the Trimming Process in Hot Stamping of T-Shaped Parts

Kim, Heung-Kyu,Shim, Hyun-Bo,Cha, Baeg-Soon,Song, Ga-Hyeong,Kim, Hyung-Jong Korean Society for Precision Engineering 2018 International Journal of Precision Engineering and Vol.19 No.5

Blank optimization in stamping is a way to reduce the cost of unnecessary material consumption or subsequent trimming operations by acquiring the final target part in a single forming process. There have been many studies on blank optimization in room temperature stamping, but few studies have yet been conducted in hot stamping. In this study, a blank shape optimization was conducted for a T-shaped part simulating a body center pillar. A finite element analysis (FEA) for the hot stamping process was performed using an appropriately assumed initial blank shape, and the blank shape was updated based on the shape error between the outline of the deformed blank obtained from the FEA and that of the target part. The shape error was calculated by applying the modified radius vector method. Hot stamping test was carried out using the optimal shaped blank predicted by the FEA. It was confirmed that the outline of the deformed blank obtained by the actual test was very close to the outline of the target part. From the results of this study, it can be seen that the blank optimum design technique at room temperature stamping can be applied to the case in hot stamping.

Infl uence of Process Variables on the Stamping Formability of Aluminum Wing Nose Rib

정호승,박상후,Won Sang Cho 한국정밀공학회 2019 International Journal of Precision Engineering and Vol.20 No.4

Ribs are the forming components of the framework of an airplane wing. The nose ribs studied have a U-shaped geometry that consisted of a flat plate, a curved flange with various radius of curvature, and straight flange, and were produced by a stamping process. During stamping, some defects such as thinning, thickening, wrinkling, and springback may occur. To design a forming tool that produces good quality, it was essential to understand the influence of process variables. This study evaluated the influence of stamping process variables on the formability of the nose rib for prevention of excessive thinning and control of the springback phenomenon. Three important process variables namely, blank holder gap, die corner radius, and clearance between the die and the punch were analyzed during an Al-2024-O nose rib stamping. The stamping simulation was a nonlinear problem in nonlinear behavior of solid materials and contacts, which was applied to an elastic–plastic material employed with contact behavior conditions. A DOE design matrix was generated by a full factorial design with every combination of the design variables. The main process variables affecting the multi-objective function, i.e., thickness reduction ratio and springback amount were suggested through main effect analysis, along with the stamping simulation. An experiment was performed to verify the validity of the simulation results. Results indicated that the thickness reduction rate and the springback amount predicted by the simulation were in good agreement with the experimental results. The locations where the maximum thickness reduction occurred, the maximum deformation amount caused by springback, the blank holder force, and the initial blank shape were suggested in this paper. The influence of the process variables will be considered as a reference for improving the quality of the nose rib.

고세장비 연속주름을 갖는 박판구조물 제작을 위한 다단성형공정 개발

최성우(Sung-Woo Choi),박상후(Sang-Hu Park),정호승(Ho Seung Jeong),조종래(Jong-Rae Cho),민준기(June Kee Min),김현준(Hyun June Kim),폴 윌리암(Paul Willians) 대한기계학회 2009 대한기계학회 춘추학술대회 Vol.2009 No.11

Stamping process is widely used in the fabrication of various sheet-parts for vehicle, airplane, and electronic devices by the merit of low processing cost and high productivity. Among the sheet metal parts, in recent the use of thin sheets having corrugated structures is rapidly increased with relation to the energy devices; for instance, heat exchanger and fuel cell. However, it is very difficult to make the corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, multistep stamping (MSS) process was proposed in this work; sequential lineup as the 1<SUP>st</SUP> stamping, heat treatment, and the 2<SUP>nd</SUP> stamping. By the MSS, we got successful results in the fabrication of very thin corrugated structures which can be applicable to a plate-type heat exchanger.

판형 열교환기에 적용 가능한 고세장비 연속주름 구조를 갖는 박판구조물 제작

최성우(Sung-Woo Choi),박상후(Sang-Hu Park),민준기(June Kee Min),정호승(Ho Seung Jeong),하만영(Man-Young Ha),조종래(Jong-Rae Cho) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.5

Stamping process is widely used in the fabrication of various sheet-parts for vehicle, airplane, and electronic devices by the merit of low processing cost and high productivity. Among the sheet metal parts, in recent the use of thin sheets having corrugated structures is rapidly increased with relation to the energy devices; for instance, heat exchanger and fuel cell. However, it is very difficult to make the corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, multistep stamping process was proposed in this work; sequential lineup as the 1<SUP>st</SUP> stamping, heat treatment, and the 2<SUP>nd</SUP> stamping. By multi-stamping, we got successful results in the fabrication of very thin corrugated structures which can be applicable to a plate-type heat exchanger.

Dry-Stamping-Transferred PC₇₁BM Charge Transport Layer via an Interface-Controlled Polyurethane Acrylate Mold Film for Efficient Planar-Type Perovskite Solar Cells

Ahn, Sunyong,Jang, Woongsik,Park, Soyun,Wang, Dong Hwan American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.18

<P>The study of interlayers is important to enhance the performance of inverted perovskite solar cells (PSCs) because interlayers in PSCs align energy levels and improve charge transport. However, previous research into applying interlayers for PSCs has focused only on wet-coated methods, such as spin coating, to form the interlayer. Here, we fabricated planar-type PSCs deposited with a 6,6-phenyl-C-71 butyric acid methyl ester (PC71BM) layer onto a CH3NH3PbI3 (MAPbI(3)) layer by stamping transfer through a relatively dry process condition. We demonstrated the effects of a stamping-transferred PC71BM layer using polyurethane acrylate (PUA), the surface energy of which was modified by 2-hydroxyethyl methacrylate (HEMA) to increase the transfer reproducibility. In PSCs with a stamping transferred PC71BM layer, we observed an enhanced J(SC) and a comparable power conversion efficiency (PCE), which were caused by an enhanced coverage of the electron transport layer onto the MAPbI(3) layer with preserved crystallinity, which occurs owing to improved electron mobility and exciton dissociation. The optimized device PCE through the dry-transferred PC71BM exhibited a J(SC), fill factor, and PCE of 21.65 mA/cm(2), 76.0%, and 15.46%, respectively. Moreover, morphological analysis and electrical measurements confirmed the improved durability of dry-stamping-transferred PSCs.</P>

Hydrophilic polyurethane acrylate and its physical property for efficient fabrication of organic photovoltaic cells via stamping transfer

Kim, K.M.,Jang, W.,Mun, S.C.,Ahn, S.,Park, J.J.,Kim, Y.Y.,Kim, E.,Park, O.O.,Wang, D.H. Elsevier Science 2016 ORGANIC ELECTRONICS Vol.31 No.-

<P>Recently, stamping transfer process using by soft mold or film has been considered by promising technology to solve the drawbacks of spin coating such as deposition of large area and specific region, reducing the material loss, and multi-staking device structures. For the previous researches, polyurethane acrylate (PUA) stamp was essentially treated the 1H, 1H, 2H, 2H-Perfluorooctyltrichlorosilane (FOTS) for self-assembled monolayer (SAM) onto the Si wafer to modify surface energy. Because the FOTS is known as corrosive material, it is necessary to develop the intrinsic property of PUA with environment friendly. In this research, we investigates non-FOTS based PUA stamping transfer and the different surface energy properties that result in various physical phenomena when used for organic photovoltaics. To transfer the material, the energy release rate (G) between the PUA and the coated material should be smaller than the G between the coated material and the substrate. As a result, hydrophilic PUA was used to reduce the interaction between the PUA and the organic bulk heterojunction (BHJ) layer to transfer the BHJ layer from the PUA stamp to a PEDOT:PSS-coated ITO-substrate. 2-Hydroxyethyl methacrylate (HEMA) is included as the reactive diluent to reduce the PUA viscosity, and the contact angle was measured to compare the surface property between the reference PUA and the HEMA-PUA. The stamping-transferred BHJ device exhibits a 95% relative efficiency (2.9%) when compared to that obtained when using a spin-coating process, which is considered as a good alternative to fabricate optoelectronic devices. More importantly, we have found a decrease in the fill factor (64%-58%) and a comparable performance (3.0%-2.9%) derived from the increase in the charge recombination and resistance during the stamping transfer. (C) 2016 Elsevier B.V. All rights reserved.</P>

고세장비 연속주름을 갖는 박판구조물 제작을 위한 다단성형공정 개발

최성우(Sung-Woo Choi),박상후(Sang Hu Park),정호승(Ho Seung Jeong),민준기(June Kee Min),정재헌(Jae-Hun Jeong),조종래(Jong-Rae Cho),김현준(Hyun June Kim),폴윌리암(Paul Willians) 대한기계학회 2010 大韓機械學會論文集A Vol.34 No.2

스탬핑 프로세서는 고생산성과 낮은 가격으로 인해 자동차 차제나 항공기 부품, 그리고 전자제품 등 다양한 장치에 널리 이용된다. 최근에 에너지 산업과 연관되어 연료전지 분리판, 열교환기 등에 사용되는 주름구조를 가지는 박판의 응용이 급속히 증가되고 있다. 그러나 복잡한 형상 때문에 주름구조물을 한번의 성형으로 만들기가 매우 어렵다. 따라서 본 연구에서는 다단성형공정을 이용하여 성형성을 향상시키는 방법을 제안하였다. 1 차 박판성형 후 열처리를 통하여 가공경화 부분을 제거하고 다시 성형하는 방법으로 복잡하고 실용성이 높은 박판구조물 제작이 가능하도록 하였다. 본 연구에서는 제안한 방법을 검증하기 위하여 판형 열교환기에 응용이 가능한 두께 100 ㎛를 가지는 박판주름구조를 제작하고 공정변수를 연구하였다. The stamping process is widely used in fabricating various sheet-parts for vehicle, airplane, and electronic devices due to its low processing cost and high productivity. Recently the use of thin sheets with corrugated structures has rapidly increased for the production of energy devices, e.g., heat exchangers and fuel cells. However, it is very difficult to make corrugated structures directly in the stamping process due to their geometrical complexity. To solve this problem, this paper proposes a multi-step stamping process with a combined heat treatment process: a sequence of the first stamping, heat treatment, and second stamping. By multi-stamping, we obtained successful results in fabricating very thin corrugated structures with thicknesses of 100 ㎛; these are applicable as part of a plate-type heat exchanger.

Microstructural control of hot rolled strips and their tensile strengths after hot stamping process

하원,이창훈,박철재 대한기계학회 2015 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.29 No.1

The influence of microstructure of hot rolled strips on tensile property after hot stamping was investigated using boron-bearing steel of1470 MPa grade for hot stamping. Hot rolled strips with two kinds of microstructures were produced by mill trial based on a timetemperaturetransformation (TTT) diagram that resulted from a dilatometric experiment. The first had a ferrite-pearlite banded microstructureand the other had a bainitic microstructure. The strip with bainite had a higher tensile strength after hot stamping compared withthe tensile strength of the strip with ferrite-pearlite banded microstructure after hot stamping. The former almost fully transformed tomartensite after hot stamping, while the latter transformed to partial martensite and ferrite that originated from the inhomogeneous hardenabilityof the ferrite-pearlite banded structure due to segregation of alloying elements such as carbon and manganese.

Conduction Heating of Boron Alloyed Steel in Application for Hot Stamping

Weikang Liang,Yong Liu,Bin Zhu,Minglin Zhou,Yisheng Zhang 한국정밀공학회 2015 International Journal of Precision Engineering and Vol. No.

In traditional hot stamping process, heating of the sheet by radiation heating occupies most of cycle time, which limits the application of hot stamping in automotive industry. Thus a faster heating method has great significance on the hot stamping. The conduction heating overcomes shortage of the radiation heating because of higher heating rate and greater energy efficiency. It attracts increasing attention in the application of heating blanks in hot stamping. In the present study, a movable conduction heating device on die was designed in terms of the Joule’s Law. Heating experiments of boron alloyed steel were performed using the developed device. Heating rate and uniform temperature region were investigated in the non-heat preservation condition (NHPC) and the heat preservation condition (HPC). The results revealed that in the HPC, the heating rate was improved by 13.1 °C/s. In addition, the length of the uniform temperature region was lengthened by 15 mm. It was demonstrated that the HPC was preferred. Furthermore, it was indicated that the mechanical properties of the blanks in uniform temperature region of the conduction heating were also superior to that of the radiation heating.