On the determination of the Young’s modulus of thin films using indentation tests

Abstract

The main difficulty with the characterization of thin coatings using depth-sensing indentation tests is related to the determination of the contributions of the substrate and the film to the measured properties. In this study, three-dimensional numerical simulations of the Vickers hardness test are used in order to examine the influence of the elastic and plastic properties of the substrate and the film on the composite's Young's modulus results. The hardness of the film is equal to or higher than the substrate hardness. A study of the stress distributions and the indentation geometry of composites, film/ substrate, was performed, taking into account the relative mechanical properties of the film and substrate. In addition, stress evolution during indentation was studied, in order to quantify the critical indentation depth under which the substrate is not elastically deformed. The accurate evaluation of the Young's modulus of the films using weight functions is also examined: some of these have previously been proposed and one was introduced for this study. Two different fitting procedures were used to compare the results obtained from eight fictive film/substrate combinations using six weight functions. The first procedure, commonly used, considers the substrate's modulus as a known parameter in the fitting process. In the second, the film and the substrate's modulus are considered as unknown variables that are calculated simultaneously during the fitting process. The validity of the conclusions obtained using the fictive materials was checked by applying the weight functions to four real composites.

An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques

“…6b). Now and knowing the elastic modulus of the film, it is possible to test the robustness of the different models [3,[14][15][16][17][18][19]. All the elastic modulus values obtained in nanoindentation (Fig.…”

“…The different models developed for nanoindentation [14][15][16][17][18][19] express the relative variation of the composite reduced elastic modulus compared to that of the substrate and of the film, as a function of the indenter displacement to thickness ratio. One can notice that, in these models, the fact that a direct determination is possible for very low indenter displacements is usually neglected.…”

“…In these conditions, models are required for separating the contributions of the film and of the substrate from the measured or, often called, composite reduced modulus. These models have been formerly developed for analysing nanoindentation data by Gao et al [14], Menčik et al [15], Perriot and Barthel [16], Antunes et al [17], Doerner and Nix [18] and Bec et al [19] on the basis of the best fit of the elastic modulus variation as a function of the indenter displacement, film thickness and some adjusting parameters.…”

Mechanical Properties Evaluation of Bulk and Coated Material by Depth Sensing Indentation

“…Moreover, the DSI equipments allow evaluating, not only the hardness, but also other mechanical properties, such as the Young's modulus (Doerner & Nix, 1986;Oliver & Pharr, 1992). Other mechanical properties, such as the yield stress and work-hardening coefficient (Dao et al, 2001;Antunes et al, 2007), of bulk and coated materials can be determined from the DSI results, by applying accurate models or inverse analysis procedures. Most of the achievements reached in this domain arise from the employment of numerical tools.…”

“…The inconvenience, common to all these procedures, is the experimental use of multiple indenters. Recently, a new reverse analysis procedure, making use of results obtained with single indenter geometry, was proposed by (Antunes et al, 2007). The methodology, based on three-dimensional numerical simulations of the hardness test, is constructed in order to ensure unique results for the representative stress and the work-hardening coefficient.…”