Biaxial Work Hardening Characteristics of 6000 Series Aluminum Alloy Sheet for Large Strain Range

Deformation behavior of 0.9-mm-thick 6016-T4 aluminum alloy sheet with a high intensity of the cube orientation under biaxial tension was investigated. First, many linear stress paths in the first quadrant of stress space were applied to cruciform specimens to precisely measure the deformation behavior of the test material up to an equivalent strain of 0.04. True stress-true plastic strain curves, contours of plastic work in stress space and the directions of plastic strain rates were measured and compared with those calculated using selected yield functions. Second, in an effort to observe the plastic deformation behavior of the sample up to much larger strains over 0.1, the sample was bent and YAG-laser welded to fabricate tubular specimens with an inner diameter of 44.6mm. Using a servo-controlled tension-internal pressure testing machine, plane strain tension tests were performed. Hydraulic bulge test was also performed. The material exhibits significant differential work hardening; the Yld2000-2d yield functions with exponents of 6, 12 and 32 had the best agreement with the experimental work contours for the equivalent plastic strains of 0.002, 0.04 and 0.14, respectively.