Material modeling of 6000 series aluminum alloy sheets with different density cube textures and effect on the accuracy of finite element simulation

Biaxial tensile tests of 6000 series aluminum alloy sheet with different density cube textures were conducted using cruciform specimens. The specimens were loaded under linear stress paths in a servo-controlled biaxial tensile testing machine. The plastic orthotropy remained coaxial with the principal stresses throughout every experiment. Successive contours of plastic work in stress space and the directions of plastic strain rates were precisely measured and compared with those calculated using selected yield functions. The Yld2000-2d yield functions with exponents of 12 and 6 were capable of reproducing the general work contour trends and the directions of plastic strain rates observed for the test materials with high and low density cube textures, respectively. Hydraulic bulge tests were also conducted and the variation of thickness strain along the meridian directions of the bulged specimen was compared with that calculated using finite element analysis (FEA) based on selected yield functions. Differences in the cube texture density caused significant differences in the strain distribution of the bulged specimens, and were in good agreement with the FEA results obtained using the Yld2000-2d yield functions. It is thus concluded that the biaxial tensile testing method with a cruciform specimen is an effective material testing method for accurately detecting and modeling the deformation behavior of sheet metals under biaxial tension.