• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2009년도 춘계학술대회 논문집
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• pp.389-392
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• 2009

The application of an equivalent drawbead model(EDM) for sheet metal forming analysis, which adopts the forces instead of complex geometries in modeling the drawbead, to the numerical simulation of auto-panel stamping process is introduced in this study. In terms of the thinning and draw-in, better agreement with experimental measurements was found in EDM than in commercial code models so that the excellence of EDM in the accuracy of drawbead forces for the simulation of auto-body stampings was revealed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2000년도 춘계학술대회논문집
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• pp.26-29
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• 2000

drawbead expert models are developed for calculating drawbead restraining force and drawbead-exit thinnings which are boundary conditions in FEM stamping simulation employing the linear multiple regression method by which the deviation of drawing characteristics between drawing test and mathematical model is minimized. In order to show the efficiency and accuracy of an expert drawbead model a finite element simulation of auto-body panel stamping is carried out. The finite element simulation shows that the expert drawbead model provides the accurate solution guarantees the stable convergence and the merit in the computation time.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1999년도 추계학술대회논문집
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• pp.14-17
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• 1999

The finite element formulation is developed for predicting strain distributions and weld line movements in the forming processes of laser welded blank. The welded zone(WZ) is modelled with several narrow finite elements whose material characteristics are analytically obtained from those of base metals based on the tensile tests. In order to show the reliability and effectiveness of weld element the forming process of hemispherical dome stretching and auto-body door inner panel stamping are simulated FEM predictions show good agreements with experimental observations.

• 한국레이저가공학회:학술대회논문집
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• 한국레이저가공학회 1999년도 춘계학술발표대회 논문개요집
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• pp.29-32
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• 1999

The material properties of laser welding zone such as strength coefficient, work-hardening exponent, and plastic anisotropic ratio are analytically obtained from those of base metals based on the tensile tests. . The finite element formulation is developed for predicting strain distributions and weld line movements in the forming processes of laser welded blank. The welding zone(WZ) is modelled with the several, narrow finite elements whose material characteristics are based on the experimental results and the analytical equations. In order to show an application of the developed weld element the stamping process of auto-body door inner panel is simulated. FEM predictions are compared and showed good agreements with experimental observations.

• 한국자동차공학회논문집
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• 제9권3호
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• pp.131-142
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• 2001

A wrinkling is the instability phenomenon influenced by material properties, shape geometry, forming conditions, stress state, etc. The wrinkling is considered as a critical defect in appearance of product. Many wrinkling prediction methods using thickness strain distribution and farming analysis have been proposed. The wrinkling, however, is not easily predicted precisely by these methods. In this study, the region in the biaxial plane stress state is modeled with a rectangular plate introducing the effective dimension, and critical stress values for the wrinkling are calculated. Prediction index for the wrinkling is then evaluated by normalizing the actual stress with respect to the critical stress. In order to show the validity and efficiency of the method proposed, the wrinkling prediction for a squared sheet in the uniaxial tensile stress and auto-body front finder panel is performed.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 1996년도 자동차부품 제작기술의 진보
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• pp.97-109
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• 1996

In the present work computations are carried out for analysis of complicated sheet metal forming process such as forming of a rear hinge. Finite element formulation using dynamic explicit time integration scheme and step-wise combined Implicit/Explicit scheme are introduced for numerical analysis of sheet metal forming process. The rigid-plastic finite element method based on membrane elements has long been employed as a useful numerical technique for the analysis of sheet metal forming because of its time effectiveness. The explicit scheme in general use is based on the elastic-plastic modelling of material requiring large computation time. In finite element simulation of sheet metal forming processes, the robustness and stability of computation are important requirements since the computation time and convergency become major points of consideration besides the solution accuracy due to the complexity of geometry and boundary conditions. The implicit scheme employs a more reliable and rigorous scheme in considering the equilibrium at each step of deformation, while in the explicit scheme the problem of convergency is eliminated at the cost of solution accuracy. The explicit approach and the implicit approach have merits and demerits, respectively. In order to combine the merits of these two methods a step-wise combined implicit/explicit scheme has been developed.