Stress Corrections After Necking Using a Two-Parameter Equation for the Radius of Curvature

Abstract

Uniaxial tensile tests were conducted at room temperature, 100 °C and 150 °C, for obtaining necking-corrected stress–strain curves until fracture. The necking correction is based on specimen contours estimated from images recorded during testing. Axisymmetric tensile specimens of an AA6082 alloy artificially aged at different times were tested. The radius of the minimal cross-section area and the necking-curvature radius R were experimentally obtained. For all cases, a/R as a function of the strain after the onset of necking ɛ − ɛu shows a characteristic nonlinear transition into a linear asymptotic relationship. Based on the tests, a new two-parameter curve was proposed for the a/R relationship. The slope of the linear part of the new model equals 1.1, as in the Le Roy model. An additional parameter is introduced, which controls the part of the curve with the nonlinear transition. This region increases at increased testing temperature and varies for different aging times. The proposed equation and the necking corrections were verified by finite element modeling analysis.