An internal-state-variable based viscoelastic-plastic model for polymers

Abstract

In this study, a new viscoelastic-plastic constitutive model which has been formulated by utilizing the formalism of stress-like internal state variables is introduced. The developed constitutive equation allows for a good description of the inelastic material response of polymeric materials over a wide range of strain rates. An algorithm for numerical integration of the model equations has been derived. The FE implementation of the constitutive equation is widely discussed and the results of solving several exemplary problems are presented.

Numerical implementation of finite strain elasto-plasticity without yield surface

“…The basic concepts of the considered framework were first introduced as a part of a viscoplastic constitutive model for polymeric materials, cf Suchocki (2015). Further research proved applicability of the proposed theory to model the material response of metals (Suchocki and Skoczylas, 2016).…”

“…However, the concept of an intrinsic time adopted therein and defined as the arclength in the nine-dimensional strain space has been slightly modified for the purpose of present considerations (cf Suchocki, 2015;Suchocki and Skoczylas, 2016). The fictitious time is utilized to build a functional of the deformation history which determines the material stress response and is analogous to the history functional known from the viscoelasticity theory (e.g.…”

“…The FE implementation was discussed as well. A viscoplastic model containing an elasto-plastic term without a yield condition was also proposed and implemented into FEM by Suchocki (2015). This model was formulated in the reference configuration using the material description and presents itself a generalization of the hyperelasticity theory.…”

“…This model was formulated in the reference configuration using the material description and presents itself a generalization of the hyperelasticity theory. The approximation of the Material Jacobian (MJ) tensor proposed by Suchocki (2015) proved to be accurate enough for the purpose of modeling the mechanical response of polymers. However, application of the same constitutive modeling framework to metallic materials results in much higher values of the model constants.…”

Finite strain formulation of elasto-plasticity without yield surface: theory, parameter identification and applications

“…In the present work, a finite strain formulation of plasticity without the yield surface, previously introduced by Suchocki (2015), is analyzed upon its ability to capture the inelastic response of metals. In order to clearly lay out basic theory assumptions, the infinitesimal strain formulation is described first.…”