Stress analysis of the deep drawing process of copper alloy plates

The most important method to obtain cup shaped parts from sheet metal plates is deep drawing. Parts which have a base thickness greater than wall thickness, such as cartridge cases, are produced by ironing method. At the ironing process the thickness of the plate is equal to the base thickness of the work piece. Wall thickness is brought to the desired value by a number of ironing processes, while base thickness does not change. In this study, the problems encountered at the deep drawing processes two different cartridge cases are analyzed with finite element method and the results and solutions were compared with the actual results. First of all, the effect of friction coefficient is studied and it is identified that the decrease of friction coefficient decreases the force required for the deep drawing process. Actually this coefficient can be reduced by having better surface finish at the stamp and dies and also by using better lubricants. The wear of the stamp and dies also increases the friction. To prevent this dies and stamps can be coated. Another topic examined in this study is, how much the wall thickness can be reduced while producing cup shaped parts from sheets. According to the simulation results the ratio of the wall thickness of the work piece after deep drawing and the thickness of the plate can be maximum 0,964. This reduction reduces the number of the ironing processes after deep drawing. When the optimum reduction ratio is studied it is found that the ratio can be 63 percent maximum, according to the analysis results.Practically when the reduction ratio is 63,5 percent, the work piece is cracked and the deep drawing process did not result. When this ratio is reduced to 60,6 percent the problem was fixed and the operation did result properly. According to these results it is concluded that the ratio of 60 percent is proper and secure.