• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.289-293
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• 2007

The effect of temperature on the forming limit diagram was investigated for AZ31B magnesium alloy sheet through the limit dome height test in the range from room temperature to $300^{\circ}C$. The formability of AZ31B sheet was improved significantly according to the increasing temperature. Also we studied the springback characteristics through the 2D draw bending test with different blank holding forces at elevated temperatures. Springback quantity was considerably reduced as temperature went up. The blank holding force in the range used, however, had little influence on springback. Experimental results obtained in this study may provide a material database for AZ31B sheet.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.10a
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• pp.67-69
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• 2007

Unusual mechanical constitutive behavior of magnesium alloy sheets has been implemented into the finite element program ABAQUS via user material subroutine. For the verification purpose, the springback of AZ31B magnesium alloy sheet was measured using the unconstrained cylindrical bending test of Numisheet'2002. In addition to the developed constitutive models, the other two models based on isotropic constitutive equations with tensile and compressive properties were also considered. Preliminary comparisons have been made between simulated results by the finite element analysis and corresponding experiments and the newly proposed model showed enhanced prediction capability in springback prediction.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1379-1380
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• 2011

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2003.10a
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• pp.117-120
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• 2003

Warm deep drawing which is one of the new forming technologies to improve formability of sheet metal is applied to the cylindrical cup drawing of Mg-alloy sheet metal. In experiments the temperature of die and blank holder is varied from room temperature to $300^{\circ}C$, while the punch is cooled by circulation of coolant to increase the fracture strength of workpiece on the punch corner area. Test material chosen for experiments is AZ31 magnesium sheet metal. Teflon film as a lubricant is used on both sides of a workpiece. The limit drawing ratio as well as thickness distributions of drawn cups are investigated and validity of warm deep drawing process is also discussed.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.05a
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• pp.385-388
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• 2005

The use of magnesium alloys meets the need of reducing weight of componests(especially in automotive and aerospace industry) keeping unmodified their mechanical properties. The adoption of magnesium alloys in sheet forming processes is still limited, due to their low formability at room temperature caused by the hexagonal crystal structure. In this study, the authors aim to understand the process condition which can lead to a successful improvement in the formability of a magnesium alloy(AZ31). Experiment and simulations of deep drawing were doned at various warm temperature for the blank and tool(holde and die)while the punch was kept at room temperature by cooling wale. in order to confirm that the deep drawing performance of magnesium alloy can be considerably enhanced with using the local heating and cooling technique.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2016.11a
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• pp.125.2-125.2
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• 2016

마그네슘 판재는 많은 연구자들에 의해 합금, 성형성, 표면처리성의 진보로 인해, IT 부품 및 자동차 부품화에 성공하고 있다. 그러나, 아직도, 자동차 부품으로의 양산화 실적은 매우 열약하고, 수만대급의 자동차 시장 진입을 위해서는, 개발해야할 기술이 많다. 본 연구 발표에서는, Mg 자동차 부품 양산화를 위해서 현재의 표면처리 상태를 되짚어보고, 앞으로 개발이 되어야할 기술들에 대해 소개함으로써, Mg 판재의 자동차 부품화에 있어서 표면처리 기술 개발의 중요성에 대해 소개하고자 한다.

• Proceedings of the KWS Conference
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• 2008.05a
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• pp.47-47
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• 2008

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.1387-1388
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• 2013

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.1313-1314
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• 2011

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2007.05a
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• pp.298-301
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• 2007

Magnesium alloy sheets have unique mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening response. The unusual mechanical behavior of magnesium alloys has been understood by the limited symmetry crystal structure of HCP metals or by deformation twinning. In the present study, the continuum plasticity models considering the unusual plastic behavior of magnesium alloy sheet were derived for a finite element analysis. A new hardening law based on two-surface model was developed to consider the general stress-strain response of metal sheets such as Bauschinger effect, transient behavior and the unusual asymmetry. Three deformation modes observed during the continuous tension/compression tests were mathematically formulated with simplified relations between the state of deformation and their histories. In terms of the anisotropy and asymmetry of the initial yield stress, the Drucker-Prager's pressure dependent yield surface was modified to include the anisotropy of magnesium alloys.