Effect of die profile on the wrinkling behaviour of three different commercially pure aluminium grades when drawn through conical and tractrix dies

Abstract

Experiments have been carried out to evaluate the onset of wrinkling behaviour in three grades of annealed commercially pure aluminium sheets namely ISS 19000, ISS 19600 and ISS 19660 having thickness 2 mm, while drawing them through conical and tractrix dies. The deep drawing of circular blanks of different diameters of the previously mentioned sheet metals has been carried out using flat bottom punch. The analysis of the experimental data has revealed that the onset of wrinkling takes place when the ratio of the plastic strain increments (dε_r/dε_θ) reached a critical value. It has been also found that the measured strains followed non-linear paths in the wrinkling limit diagrams. Further, it has been observed that the aluminium grade having high strain hardening index value, low yield stress and high normalized hardening rate shows better resistance against wrinkling. Drawing with the tractrix die shows better resistance against wrinkling as compared to drawing with the conical die.