One-dimensional elasto-plastic material model with damage for a quick identification of the material properties

Abstract

Material parameters for elastic, plastic and damage behavior of low-molecular-weight epoxy resin CHS-EPOXY 520 hardened with CHS-P 11 are identified in the paper. Uniaxial cyclic static tests were performed on specimens in line with the ASTM standard D638 -10 using a Zwick Roell/Z050 test machine with a BTC-Exaclbi.001 clip-on biaxial extensometer. Poisson's ratio and tensile strength were calculated directly from the test results. Other parameters were identified using a combination of a one-dimensional material model, which assumes the infinitesimal strain theory and takes into account elastic, plastic and damage behavior and the optimization method. The model is coded in Python and the values of the material parameters are identified using the optiSLang optimization software. The optimization process uses simple design improvement and gradient-based algorithms with the goal to minimize the difference between the force-elongation curves recorded during the tests and those calculated with the proposed model. Keywords: epoxy, identification, optimization, elasticity, plasticity, damage V~lanku so opredeljeni parametri epoksi smole z majhno molekulsko maso CHS-EPOXY 520, utrjeno z CHS-p 11, pri elasti~nem, plasti~nem obna{anju in pri po{kodbi. Enoosni stati~ni cikli~ni preizkusi so bili izvedeni na vzorcih, ki ustrezajo ASTM standardu D638-10, z uporabo Zwick Roell/Z050 preizkusnega stroja z name{~enim dvoosnim ekstenziometrom BTC-Exaclbi.001. Poissonov koli~nik in natezna trdnost sta bili izra~unani neposredno iz rezultatov preizkusov. Drugi parametri so ugotovljeni s kombinacijo enodimenzijskega modela materiala, ki predpostavlja infinitezimalno teorijo napetosti in ki upo{teva obna{anje v elasti~nem, plasti~nem in ob po{kodbi ter metodo optimizacije. Model je kodiran v Pythonu in vrednosti parametrov materiala so ugotovljene z uporabo optiSLang programske opreme za optimizacijo. Proces optimizacije uporablja enostavno izbolj{anje oblike in algoritme, ki temeljijo na gradientu, s ciljem po zmanj{anju razlike med krivuljo silaraztezek zabele`ene med preizkusom in izra~unane z uporabo predlaganega modela.