Finite Element Analysis of Magnesium AZ31 Alloy Sheet in Warm Deep-Drawing Process Considering Heat Transfer Effect
 
Abdel-Wahab El-Morsy * and Ken-ichi Manabe **
* Metals Technology Sector, Central Metallurgical Research and Development Institute, Cairo, Egypt
** Department of Mechanical Engineering, Tokyo Metropolitan University, Tokyo, Japan
 

In this study, finite element (FE) analysis of warm deep-drawing process of AZ31 magnesium alloy was initiated with following two primary objectives. First, to have first-hand knowledge of warm deep- drawing process considering heat transfer effect between blank and die components (die and blank holder) and second to investigate the improvement of drawability of magnesium alloy. Fig. 1 shows the FE model of deep-drawing process. Table 1 shows the temperatures of the deep-drawing components for the two models on forming temperature conditions. Fig. 2 shows the material properties, K, n, and m as a function of temperature of AZ31 used in the FE simulation.

Figure 3 shows the influence of heat transfer in warm deep-drawing process on the deformation profile. It is obvious that localized thinning occurred in the formed blank in the case of uniform temperature (Model II) at early stage. Conversely, the blank in model I with the heated flange part and cooled punch part considering heat transfer is drawn successfully without any localized thinning and the cup height is higher compared with the second model. The temperature distribution of flange part and its heat transfer have strong effect on the final deformation profile of the process.

Figure 4 shows the estimated temperature distribution along the deformed part of warm deep drawing with heat transfer (model I). From this figure, the suitable temperature condition for a success of the process can be estimated, and the importance of considering the heat transfer also can be understood.

Figure 5 shows the effect of punch speed on the temperature distribution along the deformed part. The simulation is conducted at three different speed 135, 270, and 1350 mm/min. With increasing the punch speed, the temperature of the deformed part at the punch bottom is higher than room temperature which means there is a gap between the punch and blank in this area. Increasing the temperature at the punch bottom leads to the decrease in the strength of the blank and the thinning can take place at this area. The heat transfer is more effective with low punch speed than that of high punch speed due to the effect of long time dictated by low punch speed. The maximum cup height with low punch speed is higher than that with high punch speed. This may be due to the effect of the heat transfer on the warm deep-drawing process.

[Published in Materials Letters, Volume 60, Issue 15 (2006), pp.1866•1870]
Table 1 Temperature distribution in the two models


Fig. 1 Illustration of FE model of warm deep drawing process used

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Fig.2 Material properties of AZ31 used in FE simulation.



Fig. 3 Effect of temperature distribution and heat transfer on the deformation profile of warm deep-drawing process.


Fig. 4 Temperature distribution of warm deep-drawing process along deformed part at punch speed 135 mm/min.

 
Fig. 5 Temperature distributions along deformed part at three different punch speeds (number of steps=calculated forming time/s).