کلیدواژهها

Isotropic hardening, kinematic hardening, strain range, hysteresis curve, optimization

چکیده

Although attempts have been devoted to consider the strain range effect in the material models, identification of material constants for accurate modeling the material response under cyclic loading within a wide range of strain amplitude is
still a challenge. The experiments show that the cyclic stress–strain curves are severely dependent on the strain range
for ductile metals. In most of the cyclic material models, only the stabilized cycle is considered to compute the constants
of the models. Considering this strategy in the simulation of ductile metals subjected to cyclic loading may lead to erroneous results particularly for the initial cycles of the loading. In this study, straincontrolled tests were conducted to
study the cyclic behavior of oxygenfree high thermal conductivity pure copper at different strain ranges. Each cycle of
the hysteresis curve was divided into a tensile and a compressive half cycle. The yield stress and the constants of the
fourrule Chaboche kinematic hardening model were computed for each half cycle using an automated program developed based on the genetic algorithm optimization. The results indicated that the constants of Chaboche model were
dependent on the strain range and the accumulated plastic strain. Therefore, new strain range–dependent relations for
isotropic and kinematic hardening conditions were proposed and the constants of the relations were computed. The
proposed model could accurately simulate the stress–strain curve of the hysteresis loop from monotonic loading to the
stabilized cycle.
