International Journal for ENGINEERING MODELLING
Vol. 12, No. 1-4, 1999.
On the increase of accuracy in numerical modelling of metal plasticity
Zeljko Somodji(1), Jurica Soric(2) and Ivo Alfirevic(2)
(1)Faculty of Textile Technology, University of Zagreb, Prilaz baruna Filipovica 30,
HR-10000 Zagreb, CROATIA
(2)Faculty of Mechanical Engineering and Naval Architecture, University of Zagreb,
Ivana Lucica 5, HR-10000 Zagreb, CROATIA; e-mail: soric@fsb.hr
SUMMARY
A yield criterion is proposed suitable for accurate numerical modelling of metal plasticity
when there are deviations from classical theories in the actual yield curve. The new
criterion is obtained by enhancing the von Mises yield curve with a trigonometric series
in the deviatoric plane. Limits for the admissible values of correction amplitudes in the
sense of convexity postulate are given for lower numbers of correction harmonics. Consistent
tangent material matrix is derived in the form suitable for incorporating the proposed yield
criterion. An example presenting a perforated tension strip demonstrates the influence of the
yield function's deviation from von Mises theory on the calculated displacements and spread
of the plastic zones. No significant loss in computational performance is recorded when von
Mises is replaced by the new yield criterion.