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Computational modeling of viscoplastic polymeric material response during micro-indentation tests

Authors
  • O’Connor, Joan1
  • Santos, Bianca Bastos dos2
  • Borges, Lavinia1
  • Costa, Marysilvia Ferreira da2
  • Castello, Daniel Alves1
  • 1 Federal University of Rio de Janeiro, UFRJ, Rio de Janeiro, RJ, 21945-970, Brazil , Rio de Janeiro (Brazil)
  • 2 Federal University of Rio de Janeiro UFRJ, Rio de Janeiro, RJ, 21941-598, Brazil , Rio de Janeiro (Brazil)
Type
Published Article
Journal
Journal of the Brazilian Society of Mechanical Sciences and Engineering
Publisher
Springer Berlin Heidelberg
Publication Date
Jul 30, 2020
Volume
42
Issue
8
Identifiers
DOI: 10.1007/s40430-020-02511-2
Source
Springer Nature
Keywords
License
Yellow

Abstract

The computational modeling of instrumented indentation tests used to characterize material properties is challenging. It is mainly due to the computational techniques demanded to couple the complex physical mechanisms involved, such as, for example, the time-dependent inelastic material response to loads during contact. Therefore, this work aims to simulate the mechanical response of the poly vinylidene fluoride (PVDF) during a micro-indentation test considering a viscoplastic material model, and a prescribed load approach, using the finite element method. Further, model validation is performed based on experimental data measured during the contact between the indenter and the PVDF. Numerical analyses were performed using COMSOL Multiphysics finite element software considering the loading scheme of the experimental tests of 800 mN/min rate during loading and unloading, and a 400 mN constant load, held by 30 s. Finally, a viscoplastic Chaboche constitutive model is presented considering two cases: (1) a perfectly plastic behavior, and (2) a nonlinear isotropic hardening behavior based on Voce and Hockett–Sherby exponential laws. While the latter models exhibit some discrepancy in capturing the experimental behavior, the former one has shown excellent agreement with the load-depth curves obtained experimentally, achieving the best fitting for the set of Chaboche parameters: A=1s-1,n=4.62\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$A=1\,{\mathrm{{s}}}^{-1}, {n}=4.62$$\end{document} and σref=132\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\sigma _\mathrm{{ref}}=132$$\end{document} MPa. Moreover, several phenomenological features of viscoplastic behavior such as rate dependence, plastic flow (or creep) and stress relaxation were accurately provided by the Chaboche model when describing the behavior of the PVDF material.

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