Modeling of aluminum alloy sheets based on new anisotropic yield functions

New anisotropic models (Yld2000-2d, Barlat et al. [F. Barlat, J.C. Brem, J.W. Yoon, K. Chung, R.E. Dick, S.H. Choi, F. Pourboghrat, E. Chu, D.J. Lege, Plane stress yield function for aluminum alloy sheets, Int. J. Plastic. 19 (2003) 1297-1319]; Yld2004-18p, Barlat et al. [F. Barlat, H. Aretz, J.W. Yoon, M.E. Karabin, J.C. Brem, R.E. Dick, Linear transformation-based anisotropic yield functions, Int. J. Plastic. 21 (2005) 1009-1039] ) that accurately describe the anisotropic behavior of aluminum alloy sheets were implemented in a finite element code, LS-DYNA User MATerial subroutine (UMAT). The Yld2004-18p especially, requires sufficient experimental input taken every 15° from the rolling direction. As planar anisotropic behavior, earing simulation was carried out in order to show the capability of Yld2004-18p to predict more than four ears. A general automotive panel simulation which covers forming, trimming and springback was performed to show the generality and efficiency of the two new yield functions. The simulation results led to the excellent predictions.