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노학곤(Hakgon Noh),윤준석(Junseok Yoon),송우진(Woojin Song),강범수(Beomsoo Kang),김정(Jeong Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
Electromagnetic forming(EMF) is an impulse or high-speed forming technology using pulsed magnetic field to apply Lorentz forces to workpiece. Generally, EMF have better formability characteristic due to its high-speed forming condition. in this paper, numerical simulation were performed to investigate formability enhancement of EMF. Gurson-Tergaard-Needleman(GTN) plasticity material model was used to verify the effect of the tool-sheet interaction which is main reason of formability enhancement. A free bulging and a conical forming die with 0.7T AL1050sheet was used to predict damage evolution based on GTN model. The impact between the tool and sheet results in combined stress states such as compressive hydrostatic stresses. In conclusion, the damage reduction because of the tool-sheet interaction can be the main factor increasing formability in EMF process.
냉간압연강판의 성형성 예측을 위한 실험 및 수치해석적 파손기준 비교
윤준석(Junseok Yoon),노학곤(Hakgon Noh),송우진(Woojin Song),강범수(Bemsoo Kang),김정(Jeong Kim) 한국자동차공학회 2012 한국자동차공학회 학술대회 및 전시회 Vol.2012 No.11
The ability to predict the forming severity with respect to crack and failure is essential to analysis of sheet metal forming process. The forming limit diagram (FLD) is commonly used to gauge the formability of sheet metal. In this article, forming limit diagrams of cold rolled carbon steel (JIS-SPCC), which widely used to produce parts of automobile, are obtained by performing experiment and FEM simulation of the Nakajima-test. By using the GTN (Gurson-Tvergaard-Needleman) model, a failure criterion based on void evolution was examined in this FEM simulation. The parameters are determined through comparison of experimental and numerical result and acceptably can be used in GTN model using given material.