• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.235-238
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• 2005

In this study, it is investigated that the effect of material properties such as strength coefficient and strain hardening exponent on formability of AZ31 alloy sheet in square cup deep drawing process. Mechanical properties of AZ31 alloy sheet at elevated temperature $250^{\circ}C$ are obtained from uniaxial tensile tests and based on these results, a series of square cup deep drawing tests at the same temperature condition are carried out. Also, the possibilities of necking initiation is predicted by the FEM and FLD and compared with experimental results.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2011.06a
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• pp.9-10
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• 2011

• Transactions of Materials Processing
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• v.18 no.2
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• pp.112-115
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• 2009

Press forming of magnesium alloy sheet is conducted at elevated temperatures to improve the press formability due to its low formability at room temperature. At elevated temperatures, magnesium alloy sheet formability is known to be very sensitive to the strain rate. In this paper, warm deep drawing tests of magnesium alloy AZ31 sheet was conducted under double forming velocity as well as single forming velocity to examine the formability change by forming velocity profile. The observed formability improvement by double forming velocity was analyzed by using the finite element analysis.

• Transactions of Materials Processing
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• v.16 no.6
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• pp.447-451
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• 2007

The springback characteristics of AZ31B magnesium alloy sheet was investigated in OSU draw/bend test Springback is the elastically-driven change of shape of a part after forming and it should be estimated and controlled to manufacture more precise products in sheet forming. Magnesium alloy sheets have unique mechanical properties such as high in-plane anisotropy/asymmetry of yield stress and hardening response. So, there will be a difference in the prediction of springback with symmetric mechanical properties for magnesium alloy sheets. In this work, the Strip draw/bend tests were conducted with various conditions - die radius, sheet thickness and controlled tensile force and the tendency of springback angle was observed from the tests.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.285-288
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• 2009

The purpose of this study is to predict the forming limit diagram (FLD) of strain-rate sensitive materials on the basis of the Marciniak and Kuczynski (M-K) theory. The strain-rate effect is taken into consideration in such a way that the stress-strain curves for various strain-rates are inputted into the formulation as point data, not as curve-fitted models such as power function. Tensile tests and R-value tests were carried out at several levels of temperature and strain-rate from $25^{\circ}C$ to $300^{\circ}C$ and 0.16 to 0.00016/s, respectively to obtain the mechanical properties of AZ31B magnesium alloy sheet. The FLD of this material was experimentally obtained by limit dome height tests with the punch velocity of 0.1 and 1.0 mm/s at $250^{\circ}C$. The M-K theory-based FLD predicted using Yld2000-2d yield criterion was compared with the experimental results.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2006.06a
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• pp.99-102
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• 2006

In the present study, the blow forming characteristics of AZ31 sheet was investigated to test the feasibility of the practical application of wrought Mg alloys. Mg alloys have drawn a huge attention in the field of transportation and consumer electronics industries since it is the lightest alloy which could be industrially applicable. Most Mg alloy components have been fabricated by casting method. However, there have been a lot of research activities on the wrought alloys and their plastic forming process recently. Shallow cups for the small electronics cases have been stamped with warm die system. However, some technical issues will challenge Mg forming when large parts are considered with warm die system over $200^{\circ}C$. Most of all, thermal expansion of die system will deteriorate a die accuracy. On the other hand, blow forming does not have a problem with inaccuracy with die system. In this study, tensile tests were followed by blow forming at various temperature and pressure. AZ31 sheet showed a superplastic deformation behavior with extensive grain boundary sliding at the temperature above $300^{\circ}C$. However, the deformation behavior was likely to differ depending on stress condition.

• Transactions of Materials Processing
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• v.15 no.3 s.84
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• pp.232-240
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• 2006

Magnesium alloys are expected to be widely used fur the parts of structural and electronic appliances due to their lightweight and EMI shielding characteristics. While the die casting has been mainly used to manufacture the parts from the magnesium alloys, the press forming is considered as an alternative to the die casting for saving the manufacturing cost and improving the structural strength of the magnesium alloy parts. However, the magnesium alloy has low formability at room temperature and therefore, in many cases, forming at elevated temperatures is necessary to obtain the required material flow without failure. In the present study, square cup deep drawing tests using the magnesium alloy AZ31 sheet were experimentally conducted at various elevated temperatures as well as room temperature, and the corresponding finite-element simulations, which calculated the damage evolution based on the Oyane's criterion, were conducted using the stress-strain relations from the tensile tests at various temperatures. The formability predictability by the finite-element analysis was investigated by comparing the predicted damage distributions over the deformed AZ31 sheet at elevated temperatures with the corresponding experimental deformations with failures.

• Journal of Welding and Joining
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• v.30 no.6
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• pp.56-61
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• 2012

Magnesium alloy sheet which is commercially available in the market presently is AZ31B, a Mg-Al-Zn three elements alloy. AZ31B is used by being classified into AZ31B-H24 and AZ31B-O depending on temper designation. In this study, AZ31B-H24 and AZ31B-O alloy sheets with 1.25mm thickness were butt-welded using CW Nd:YAG laser. And the effect of materials on mechanical properties was investigated by tensile and hardness tests. As a result of this study, regardless of materials, the butt-welded joint did not show a significant difference in tensile strength and hardness values. However, compared with the basemetal, the AZ31B-O showed more outstanding mechanical properties than AZ31B-H24, and that is because H24 material lost the effect of work hardening during welding.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.10a
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• pp.222-222
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• 2009

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.10a
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• pp.25-26
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• 2006