An analytical solution for a linear viscoelastic layer loaded with a cylindrical punch: Evaluation of the rebound indentation test with application for assessing viability of articular cartilage

A general closed-form solution for the so-called rebound indentation test’ is obtained for a cylindrical flat-ended punch indenting a linear viscoelastic layer lying on a rigid substrate. Under the assumption of time-independent Poisson's ratio, we derive closed-form analytical expressions for the contact force (in a displacement controlled regime) and for the indentation displacement (in a load-controlled regime) and we consider in detail the case of standard viscoelastic solid. Our results indicate that the rebound displacement (in other words the indentation displacement in the load-controlled stage) is independent of the relaxed elastic modulus and Poisson's ratio, and also of the layer's thickness. Our analytical solution can be used for layered samples of arbitrary materials exhibiting viscoelastic properties; however, since the rebound indentation test has been recently suggested for assessing the viability of biomedical materials, we have applied our theoretical framework to the identification of materials parameters from experiments on articular cartilage. In this context, we have found a pretty good agreement for the rebound deformation, even until the strain becomes relatively large.

► A hybrid-type indentation test for an articular cartilage layer consisting of two stages (displacement-controlled loading stage and load-controlled observation stage, when the rebound deformation of the cartilage layer is recorded after the indenter removal) is considered. ► A general closed-form solution is obtained for a cylindrical flat-ended punch indenting a linear viscoelastic layer lying on a rigid substrate. ► It is shown that the rebound displacement is independent of the relaxed elastic modulus and Poisson's ratio, and also of the layer's thickness.