Plastic behaviour of perforated sheets under biaxial stress state

A yield criterion of sheets with a uniform triangular pattern of round holes under biaxial loading has been proposed in terms of apparent stresses. The yield criterion was confirmed by finite element analysis results in the whole range of ligament efficiency of the perforated sheet. In order to analyse stretching of a perforated sheet for dot-type shadow mask by the finite element method, a yield function which can incorporate the apparent yield stress and the apparent plastic contraction ratio has been obtained. The agreement between the measured and calculated results of stretch forming of the perforated sheet was satisfactory.