Consistent parameters for plastic anisotropy of sheet metal (Part 1-uniaxial and biaxial tests)

The anisotropy parameters for sheet metal used hitherto are mainly determined by uniaxial tensile tests. Such tests, however, do not give sufficient information about the yield locus and the forming behaviour in that range where the two principal tensile stresses are of similar magnitude like in stretch forming. The same applies for combined tensile and compressive stress like in deep-drawing. To fill these gaps, new parameters are defined. Their experimental determination is briefly discussed. The "equibiaxial yield stress" and "equibiaxial anisotropy" which refer to equibiaxial tensile stress can be determined by cross tensile tests. However, these require a special apparatus. Alternatively experiments for obtaining plane strain can be applied for determining the equibiaxial parameters indirectly. This is possible using conventional tensile testing machines. In this case also anisotropy parameters for plane-strain deformation, the "semibiaxial anisotropy" in rolling and transverse direction, can be determined.