Combined effects of strain hardening characteristics and tool geometry on the deep-drawability of square aluminum cups

The combined effects of the corner radii of square tools and the strain-har dening characteristics (n-values) on the deep drawability of square aluminu m cups were investigated. Several materials having different n-values were prepared under various annealing conditions and used in the experiments. Ty pical fractured cups were observed and classified into several types, accor ding to the location and the propagation of the cracks induced in the drawn cups. The fracture types were strongly influenced by both the n-values and the corner radii of the square punches. The maximum limiting drawing ratio was obtained under the appropriate combination of n-values and the corner radii of the square punches. However, the limiting drawing ratio decreased considerably under the following two combinations: the first, when blanks h aving higher n-values were drawn with square punches of small corner radii; the second, when blanks having lower n-values were drawn with square punch es of large corner radii. The variation in the limiting drawing ratio with n-values and punch corner radii corresponded well to the variation in drawi ng forces, fracture forces and fracture types of cups. (C) 1999 Elsevier Sc ience S.A. All rights reserved.