Non-uniformity of plastic deformation of perforated sheet metal

The problem of non-uniformity of plastic deformation of perforated sheet metal at the level of the mechanics of material deformation is discussed. The bases for the discussion were the results of experimental investigations and computer simulation. There are presented typical examples of nonhomogeneous state of stress and strain of material, of the instability of the tensile curve, non-uniform flow during deep drawing, localisation of cracking and non-uniformity of the strain distribution in the product. The effect of selected factors (such as the width and the mode of cutting out the sample, the method of making the holes) on the course of the deformation and the deformation indices, are discussed. The paper presents the results of investigations of various sheet metals with hexagonal and straight perforation. The essential part of the investigations was performed for sheets with cut out circular holes, of 3 mm diameter and for the direction of their most dense packing coinciding with the rolling direction of the sheet metal.