Analysis of spherical indentation of linear viscoelastic materials

In this article, the time-dependent spherical indentation response of a linear, isotropic, viscoelastic material to different load histories is studied. To this end, finite element computations and depth-sensing microindentation experiments using polymethyl methacrylate specimens are undertaken. The validity of viscoelastic indentation theories is assessed by comparing with the finite element and experimental results. Finally, the creep response function is extracted from the experimentally recorded indentation displacement histories and is compared with that obtained from a conventional mechanical test. It is shown that accurate characterization of viscoelastic response of materials is possible from depth-sensing indentation, which has potential applications to components with small size scales such as thin films and biological tissues.