Uticaj sile držanja pri dubokom izvlačenju tankih limova

Abstract

The formability of thin sheets by deep drawing is limited by appearance of defects of two kinds. First, there is appearance of wrinkling, and second, there is fracture, that is a crack in the critical zone of the working-piece. Wrinkling appears on the flange of the working-piece as the consequence of the activity of compressive tangential stresses. The fracture takes place after reaching the limit values of stresses, i.e. of strains in critical section in the zone of transfer of deformation force. It is possible to reduce or completely eliminate wrinkling by using sufficiently large blank holder force (BHF). However, the increase of BHF influences the increase of deformation force and thus increases the possibility for the appearance of fracture. In order to avoid such situation in which the solution of one problem causes new, more difficult problems, it is necessary to identify the most important influential factors, to give integral analysis of their influence and to give solution for the posible control over the forming process. Isolated observation of the activity of some factors (especially at numerical simulations) leads to mistakes in evaluations and conclusions.