【正文】 1993。在設計和控制拉深過程不僅取決 工件的材料，而且還取決于工件表面狀態(tài)，塑性變形力和使用的設備。其中鋁合金在沖壓車間的成形的明顯差異以被觀察得到 （ Roger， 1991 年 。 關鍵詞 : 拉深 、 內部空氣壓 、 極限 拉深 比（ LDR）， 鋁 1050 。, The relatively steep decrease in thickness at rounding part that had touched with punch nose radius reflects the local strain has been concentrated on this part. Therefore, the decrease in the degree of thickness variation at the rounding part confirms that the local strain concentration has been relaxed by air pressing. Figure 7 shows the effect of the air pressure on the drawing. loaddisplacement curves. In general, an increase in the drawing force is observed for larger blank diameters due to the enlargement of fictional interfaces such as the dieblank and blank holder blank interfaces. While the figure indicates that the maximum drawing loads are not so significantly increased even with increasing maximum blank diameters at higher air pressure. It means that the internal airpressing contribute to the reduction of drawing load possibly by reducing friction between punch and blank. In other words, the internal airpressing itself does not alter the deformation resistance of deforming sheet blanks. but has an effect on the manner of the transmission of the load at punch nose radius part and increases LOR of blank. Although the experimental conditions used in this study may not be the optimum for the highest LOR, the trends obviously shows that the internal air pressing is advantageous for higher LOR. The effectiveness of the air pressing process depends on how well the metal can be pressed .Therefore, the effect of airpressing process will be more prominent for 10 aluminum alloy sheets than mild steel sheets. 4. Conclusion The airpressing method is proved to be very effective in increasing the deep drawability of AI1050. On the basis of the experimental investigation made herein, higher air pressing guarantees higher LDR. The increased LDR is mainly caused by the relaxation effect of local strain concentration at punch nose radius area. The results that have been described above show that airpressing method also has the potential to increase the LDR of other metal alloy sheets. 11 Acknowledgements This work has been supported by the Engineering Research Center for Net Shape and Die Manufacturing (ERC/NSDM), which is financed jointly by the Korean Science and Engineering Foundation (KOSEF) 12 References Chen X. and Sowerby R., 1996, Blank Development and the Prediction of Earing in Cup Drawing, International Journal of Mechanical Science, Vol. 8, , pp. 509516. Date . and Padmanabhan ., 1992, On the Prediction of the Forming Limit Diagram of Sheet Metals, International Journal of Mechanical Science, Vol. 34, , pp. 363374. Hrivnak A. and Sobotova L.,1992, The Influence of the Deformation Aging and the Conditions of Stress on the Properties of the Deep Drawing Steel Sheet, Journal of Materials Processing Technology, Vol. 34, pp. 425430. Johnson W. and Mellor .,1983 Engineering Plasticity, 2nd Ed., Ellis Horwood, Camelot Press, UK. Kawai N. et al., 1992,Friction Behavior in the Cup Ironing Process of Aluminum Sheets., Journal of Engineering for Industry, Vol. 114, ., 1997, Prediction of the Limiting Drawing Ratio and the Maximum Drawing Load in CupDrawing, International Journal of Machine Tools and Manufacture, Vol. 37, , pp. 201213. Lange K., 1985, Handbook of Metal Forming, McGrawHill, New York, pp. 2022. Roger P., 1991, Sheet Metal Forming, Adam Hilger, New York, pp. 181242. Thiruvarudehelvan S. and Loh ., 1993, Drawing of Cylindrical and Hemispherical Cups using an Improved Tooling for FrictionActuated Blank Holding, Journal of Materials Processing Technology, V