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 materia ls by using rectangular tensile specimens. In this method only load versus thickness reduction (at the diffuse necking zone) curve is needed. This met hod has been further developed for anisotropic materials. For anisotropic m aterials, both thickness and width reduction at the diffuse necking zone sh ould be measured. In this paper, the effect of plastic anisotropy on the de formed cross-section profile has been further studied, and the proposed met hod has been experimentally verified against steel which was assumed to be isotropic (width to thickness strain ratio, r(y) approximate to 1) and alum inium alloys which were anisotropic with r(y) varied in the range 0.28 < r( y) < 0.66. It has been shown that the numerically predicted deformed cross- section shape is very close to the experimental one, measured from sectione d interrupted specimens. The true stress-strain curves determined from the rectangular tensile specimens were compared with the one determined from th e conventional round tensile specimens, and very good agreement has been ob tained. It has been found that the method using rectangular tensile specime ns gives very consistent true stress-strain curves with small scatter. (C) 2001 Elsevier Science B.V. All rights reserved.