Most identification models based on instrumented indentation rely on the knowledge of the indentation load-penetration depth curve corresponding to the bulk material. Experimentally, and especially in the case of micro and nanoindentation testing, the measured curve can be affected by low scale artefacts such as sensor sensitivity, surface roughness, imperfect indenter tip geometry and material heterogeneity, leading to incorrect identifications of the indented material's bulk mechanical properties. This work proposes an exploitation of identification models which is based on the slope of the indentation curve at indentation load values and provides accurate results which are not affected by low scale artefacts.
International audienceMost instrumented indentation theoretical studies and models consider bulk sample geometry, which implies no influence on the indentation response. In the particular case of thin samples, our previous studies have shown that the thickness has an influence on the experimental device behavior as well as on the sample and material response. This work is a numerical and experimental illustration of this particularity. Spherical macroindentation tests are performed on AISI 1095 steel samples of thicknesses varying from 0.55 to 10 mm. Experimental and numerical results are compared. Experimental limitations are investigated, and solutions to obtain results that are independent of the sample thickness and curvature are proposed. We show that the proposed solution leads to a reliable identification of the material mechanical properties of thin and moderately bent samples
International audiencePerfect indenter geometry is quite difficult to manufacture, especially in the nano and macro scales. Indentation curves obtained with imperfect indenter geometry can show strong differences with those obtained with assumed perfect indenter geometry, thereby leading to erroneous data exploitation results. This numerical study brings out the effect of imperfect spherical indenter geometry on indentation load-penetration depth curves, and on the mechanical properties identified by a reverse analysis model based on ideal spherical geometry. It is shown that a method to take account of geometrical imperfections is essential. Two correction methods based on geometrical and physical considerations are assessed, as well as the relevance of the use of the penetration data or the contact data. A method based on the equality of mean contact pressures and indenter volumes under the contact surface is found to be most relevant, as confirmed by the quality results obtained after application of a reverse analysis model. The proposed method is of particular interest in the case of the use of an imperfect indenter whose profile is accurately known
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