A NUMERICAL-EXPERIMENTAL METHODOLOGY TO CHARACTERIZE THERMOPLASTICS SUBJECT TO LARGE STRAIN USING A VARIATIONAL ELASTOPLASTIC MODEL

Francisco Luiz Bresolin¹; Bruno Klahr¹; Jakson Manfredini Vassoler¹

¹ UFRGS

doi:10.20906/CPS/CILAMCE2015-0689

Resumo

Heterogeneous strain fields due to necking occurs on nonlinear elastoplastic materials, like thermoplastics, when submitted to finite strains. The prediction of this phenomenon with an adequate constitutive model requires a non-trivial numerical-experimental procedure since the resulting force data obtained from a tensile testing is not sufficient to assure the kinematics aspects of the necking. In order to determine the constitutive response of an elastoplastic material, this paper presents a numerical-experimental methodology combining numerical methods and experimental data obtained from mechanical testing with optical measurements. A variational constitutive model for nonlinear elastoplastic materials is implemented on a finite element method code, where the experimental conditions observed in mechanical testing are reproduced in a numerical simulation. The force history, obtained from the load cell, and the displacement field of the necking region, obtained from the optical measurement system, are used in a parameter identification procedure of the variational material model. A suitable objective function is proposed in order to take into account the necking phenomenon. The proposed methodology is applied on polyvinyl chloride (PVC) specimens, where tensile tests are performed. This methodology allows to evaluate the capability of the material model to reproduce simultaneously the results of force and necking displacement field.

Palavras-chave: Non-linear materials; Optical measurement; Variational model