Determining true stress–strain curve for isotropic and anisotropic materials with rectangular tensile bars: method and verifications

Based on an extensive numerical study, the authors have recently developed a method for determining the true stress–strain curve for isotropic materials by using rectangular tensile specimens. In this method only load versus thickness reduction (at the diffuse necking zone) curve is needed. This method has been further developed for anisotropic materials. For anisotropic materials, both thickness and width reduction at the diffuse necking zone should be measured. In this paper, the effect of plastic anisotropy on the deformed cross-section profile has been further studied, and the proposed method has been experimentally verified against steel which was assumed to be isotropic (width to thickness strain ratio, ry≈1) and aluminium alloys which were anisotropic with ry varied in the range 0.28<ry<0.66. It has been shown that the numerically predicted deformed cross-section shape is very close to the experimental one, measured from sectioned interrupted specimens. The true stress–strain curves determined from the rectangular tensile specimens were compared with the one determined from the conventional round tensile specimens, and very good agreement has been obtained. It has been found that the method using rectangular tensile specimens gives very consistent true stress–strain curves with small scatter.