Abstract:
Wrinkling in the flange region has been observed during redrawing operation by a few
researchers. In the present work an analysis methodology, based on a combination of upper
bound and energy approaches, is proposed for the prediction of number of wrinkles and
minimum blankholding pressure necessary to avoid wrinkling in redrawing operation.
Thickness variation predicted by the upper bound formulation is used as input for the wrinkling analysis by assuming a suitable waveform based on geometrical and process conditions. The flange is constrained at both ends, i.e., by the blank holder profile radius and at
the die entry point (where the sheet enters into the die cavity). The waveform for present
analysis is assumed such that it has zero displacement at both ends (since it is constrained)
and the maximum amplitude of the wave at some point in between those ends. The wrinkling predicted by the present methodology seems to be reasonably accurate considering
the geometrical and process constraints of the redraw
