• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.7
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• pp.1107-1118
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• 2001

The forming limit diagram introduced by Keeler and Goodwin has been used generally to analyze the formability of sheet metal. However, path dependent forming limit curves based on the state of strain can be explained only by a single criterion which is based on the state. In this study, experimental forming limits in strain space of some metal sheets are transformed into forming limit curves in stress space. Effects of yield criterion are investigated in transforming the forming limit curves. Some important design aspects which are based on the close prediction of movements in forming limit curves during sheet forming are concluded.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.2
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• pp.30-37
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• 2020

We propose a practical method for increasing formability of a sheet metal plate using laser heat treatment (LHT) and cladding process. In this work, two kinds of process such as laser-induced heat treatment and cladding were utilized to evaluate the effect on formability of SUS316 sheets with different thickness of 1 and 3 mm. By using a vertically line-patterned tensile specimen that was LHTed or cladded on its surface, the process parameters of each surface treating method were studied and optimized. Through the basic test, we knew that the laser power of 900 W and scanning speed of 500 mm/min was the best condition for increase of formability. As the treatment results, ultimate tensile strength and elongation were increased as approximately 2.1 and 7.0%, respectively. To verify the usefulness of this work in industrial cases, we conducted a bulging test using with and without LHTed SUS316 sheet metal blanks. The results show that the bulging height of LHTed sheet was increased by 73% compared to that of the original one.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2008.10a
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• pp.349-353
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• 2008

A fundamental study on warm incremental forming of a magnesium alloy sheet has been carried out. In order to enhance the incremental formability of the magnesium alloy sheet, a local heating device was newly designed and manufactured. Through the incremental forming tests of AZ31 under various forming conditions, the effects of process parameters such as the temperature, feeding depth per cycle, and inclination angle on the incremental formability of AZ31 were investigated. In addition, conventional FLDs at elevated temperatures were constructed experimentally and applied to predict the forming failure.

• Transactions of Materials Processing
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• v.24 no.5
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• pp.348-353
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• 2015

The PEPS(Polar-coordinated Effective Plastic Strain) FLD(Forming Limit Diagram), a new type of FLD based on a polar representation of the EPS(Effective Plastic Strain), appears to be an effective solution to the problem of non-linear strain path effects. This method has the advantages of the familiar strain-based diagram for linear loading, but without the strain-hardening limitations of the stress-based diagram, or non-intuitive aspects of alternate Cartesian diagrams based on effective plastic strain. In the current study, the PEPS FLD was applied to the development process of an aluminum automobile-body panel, including the necking or crack prediction, die design, and die modification. As a result, the PEPS FLD provided improved formability of aluminum sheet as compared to deriving the potential formability with non-linearity.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.938-942
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• 1996

Despite the increasing demand for improved product design, a limited number of works have been reported in the field of sheet metal forming. In the present study, introducing the Taguchi method, an optimal and robust combination of parameters is found and a data base management system and nomograms are utilized for knowledge acquisition. The developed system is applied to a deep drawing process, Through the present study, it is shown that the developed system is useful for the design and the formability estimation of sheet metal forming processes.

• Journal of Ocean Engineering and Technology
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• v.14 no.4
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• pp.86-91
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• 2000

Numerical simulation of sheet metal forming for panels as other components has wide acceptance in the automotive industry. Therefore this paper was focused in the drawability factors (which are friction coefficient , radius of die and punch ) on the square cup deep drawing by the explicit finite elements code $PAM-STAMP^{TM}$. The computed results are compared with the experimental results to show the validity of the analysis. In order to compare the simulation results with the experiment results and predict the effect of drawability factors, the relationships between punch load punch stroke, and the relationships between thickness strain and distance are used. According to this study, the results of simulation by using $PAM-STAMP^{TM}$ will give engineers good information to access the drawability of square drawing.

• Journal of Power System Engineering
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• v.9 no.3
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• pp.66-70
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• 2005

Structural components for aerospace, electronics and automobile industry are the main applications for magnesium alloys due to their lightweight and high specific strength. 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 paper, the authors aim to improve the formability of AZ31 magnesium alloy. For this, experiment and finite element analysis on used warm deep drawing process with a local heating and cooling technique were done. Both die and blank holder were heated at various warm temperature while the punch was kept at room temperature by cooling water.

• 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 Society of Precision Engineering Conference
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• 2007.06a
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• pp.235-236
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• 2007

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2005.10a
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• pp.122-125
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• 2005

Magnesium alloys are expected to be widely used for the parts of structural and electronic applications 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.