Earing predictions based on asymmetric nonquadratic yield function

A nonquadratic yield function (Yld96; Barlat, F., Maeda, Y., Chung, K., Yan agawa, M., Brem, J.C., Hayashida, Y., Lege, D.J. Matsui, K., Murtha, S.J., Hattori, S., Becker, R.C., Makosey, S., 1997. Yield function development fo r aluminium alloy sheet. J. Mech. Phys. Solids, 45, 1727) which simultaneou sly accounts for the anisotropy of uniaxial yield stresses and r values was newly implemented in a finite element code. Yield surface shapes, yield st ress and r-value directionalities of Yld96 were investigated and compared w ith those of the previous yield function, Yld91 (Barlat, F,, Lege, D,J., Br em, J.C. 1991a. A six-component yield function for anistropic metals. Int. J. Plasticity, 7, 693). Complete formulations for Yld96 implementation and the calculation of coefficients were also discussed for the convenient use of Yld96. A 2090-T3 aluminum alloy sheet sample was modeled and earing form ation during a cup drawing test was simulated using the FEM code. The resul ts of earing and thickness strain profiles were compared with the results o btained with Yld91. Investigations were further carried out with a translat ed yield surface to account for the strength differential effect observed i n this material. Computation results with the translated yield surface were in very good agreement with experimental results. It was shown that the yi eld surface shape and translation have a significant influence on the predi ction of the cup height profile during the drawing of a circular blank. (C) 2000 Elsevier Science Ltd. All rights reserved.