FORMABILITY OF DRAWING STEELS: MEASUREMENT AND MODELLING OF THE FORMING LIMIT CURVE

M.A. BERTINETTI; J.W. SIGNORELLI; P.A. TURNER; R.E. BOLMARO; J. INSAUSTI; A. LUCAIOLI; C. GARCIA; L. IURMAN

San Nicolas

Conferencia; IAS 3rd Conference on Uses of Steel; 2006

Forming limit curves at necking and at failure for a deep drawing low carbon steel have been determined experimentally by three formability tests: uniaxial, biaxial (hydraulic bulge test) and semispherical punch drawing. The initiation of localized necking is determined in terms of the strain distribution near the defect zone where the material is either thinner or weaker. The experimental results are compared with predicted ones calculated using a rate-dependent self-consistent plasticity policristal (VPSC) model. This model can describe the mechanical behaviour on the basis of texture and dislocation structure present in the material. Sheet necking is iniciated from an imperfection represented in terms of a narrow band, following the Marciniak-Kuczynski (MK) model. The deformations inside and outside the band are assumed to be homogeneous, and conditions of compability and equilibrium are enforced across the band interfaces. The MK-VPSC model has been used to discuss the effects of the ideal texture components ({001}<110>, {112}<110>, {111}<110>, {111}<112> y {554}<225> on the initiation of localized necking. The calculation with a more realistic scale transition successfully show an improvement on the predicted FLD predicts some of the experimental tendencies which cannot be reproduce by conventional Taylor model