Mechanical analysis of indentation experiments with a conical indenter

Abstract

Conference on Instrumented Indentation Testing in Materials Research and Development , Iraklion, Greece, October 07-14, 2005International audienceThe finite element method was used to study the pyramidal indentation of elastic perfectly plastic (EPP) solids. The ratio of the effective elastic modulus, E*, to the flow stress, σ0, ranged from 2.79 (quasielastic solid) to 2790 (quasirigid perfectly plastic (quasi-RPP) solid). The frictional shear stress was taken as equal to zero or its maximal value. First we analyzed the two-dimensional indentation with a rigid axisymmetric cone (semiapical angle θ∈=∈70.3°). We determined the evolution with the indentation index, X∈=∈(E*/ σ0)cot∈θ, of the indent profile, the shape ratio, c∈=∈hc/h where h (hc) is the indentation (contact) depth, and the hardness, H. The influence of friction becomes significant for X∈>∈10. We validated our results by comparison with the results related to RPP solid and the results of three-dimensional numerical simulation of the Vickers and Berkovich pyramidal indentation for X∈=∈1, 30 and 100. A method for interpreting the results of instrumented indentations is proposed and compared with the Oliver and Pharr method

Analytical correlation of indentation experiments

“…But according to this model whose velocity field is purely radial, the sample surface remains plane (the shape factor c p = 1), H* increases steadily with X and the representative strain and strain rate have not been derived. Besides this analytical analysis, Ramond-Angélélis [5] has analyzed by the finite element method the conical indentation of EPP solids for θ = 70.3 deg and Tresca friction coefficient m = 0 and 1 ( m is the ratio between the friction shear stress and the solid maximal shear stress); her results are in good agreement with elastic and SLF analysis [6].…”

New expanding cavity model for conical indentation and its application to determine an intrinsic length scale of polymeric materials

“…The presented model does not take into account the effect of the free surface distortion (so-called, pile-up or sink-in). The resulting error can become significant for very large or, on the contrary, very small values of y E  (see, for example, Felder and Ramond-Angelelis, 2006).…”