THE SIGNIFICANCE OF THE CHANGE OF CONTACT PRESSURE IN BLANK-HOLDER ZONE IN DEEP DRAWING

Abstract

Tribological conditions in blank holder zone in deep drawing significantly influence the total forming process. The value of contact pressure in holder and die zone influences the appearance of wrinkles and tearing in the zone of forming force transfer. In standard forming processes, holder force has constant value in course of deep drawing. The paper gives results of experimental researches, realized on special researching equipment, which make possible the change of holding force during the forming process. The change of blank holding force, i.e. the change of friction force on contact surfaces of holder and sheet metal, that is die, is realized according to previously determined law, as funcion of the position of outer flange edge, i.e. time. Standard sheet metals and sheet metals with anticorosion coatings, as well as various lubricants, are used in experiments. The obtained results point to the influence of contact pressure onto the drawing force, strain distributions, forming limit etc.