Journal of Materials Research

Articles

Quantifying plasticity-independent creep compliance and relaxation of viscoelastoplastic materials under contact loading

Matthieu Vandammea1 c1, Catherine A. Tweediea2, Georgios Constantinidesa3, Franz-Josef Ulma4 and Krystyn J. Van Vlieta5 c2

a1 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139; and Laboratoire Navier (École des Ponts ParisTech; Institut Français des Sciences et Technologies des Transports, de l'Aménagement et des Réseaux; Centre National de la Recherche Scientifique), Université Paris-Est, 77455 Marne-la-Vallée, France

a2 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

a3 Department of Mechanical Engineering and Materials Science and Engineering, Cyprus University of Technology, 3603 Lemesos, Cyprus

a4 Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

a5 Department of Materials Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139

Abstract

Here we quantify the time-dependent mechanical properties of a linear viscoelastoplastic material under contact loading. For contact load relaxation, we showed that the relaxation modulus can be measured independently of concurrent plasticity exhibited during the loading phase. For indentation creep, we showed that the rate of change of the contact creep compliance can be measured independently of any plastic deformation exhibited during loading through , where a(t) is the contact radius, h(t) is the displacement of the contact probe, and Pmax is the constant applied load during the creep phase. These analytical relations were compared with numerical simulations of conical indentation creep for a viscoelastoplastic material and validated against sharp indentation creep experiments conducted on polystyrene. The derived relations enable extraction of viscoelastic material characteristics, even if sharp probes confer concurrent plasticity, applicable for a general axisymmetric contact probe geometry and a general time-independent plasticity.

(Received May 05 2011)

(Accepted August 22 2011)

Key Words:

  • Nanoindentation;
  • Polymer;
  • Elastic properties

Correspondence:

c1 Address all correspondence to these authors. e-mail: matthieu.vandamme@enpc.fr

c2 e-mail: krystyn@mit.edu

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