Abstract
A commercial AZ31 magnesium alloy sheet has been tested under proportional
biaxial tensile loading using cruciform specimens. In order to quantitatively determine the
elastic-plastic deformation behavior of the test material, the contours of plastic work and the
directions of plastic strain rates were measured over a range of equivalent plastic strain,
0.001 p
≤ε 0 ≤ 0.008. The measured work contours and the directions of plastic strain rates have
been compared with those predicted using the von Mises, Hill’48 and the Yld2000-2d yield
functions. The validity of these yield functions is discussed from viewpoints of the yield surface
shape and normality flow rule in the first quadrant of the stress space. The r-value of AZ31 was
found to increase with plastic strain. The effect of the changes in r-value on the shape of the
calculated yield locus has been discussed. Furthermore, biaxial unloading tests following biaxial
loading were carried out for several stress ratios. The nonlinearity of the stress-strain curves
during uniaxial and biaxial unloading was measured and quantitatively evaluated.
DOI Link to Publication