https://sam.ensam.eu:443 The DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material. Thu, 14 May 2026 11:16:39 GMT 2026-05-14T11:16:39Z http://hdl.handle.net/10985/8559 A contact area function for Berkovich nanoindentation : Application to hardness determination of a TiHfCN thin film CHICOT, Didier; YETNA N'JOCK, M.; PUCHI-CABRERA, Eli-Saul; IOST, Alain; STAIA, M.H.; LOUIS, G.; BOUSCARRAT, G.; AUMAITRE, R. In nanoindentation, especially at very low indenter displacements, the indenter/material contact area must be defined in the best possible way in order to accurately determine the mechanical properties of the material. One of the best methodologies for the computation of the contact area has been proposed by Oliver and Pharr [W.C.Oliver, G.M.Pharr, J.Mater. Res. 7 (1992) 1564], which involves a complex phenomenological area function. Unfortunately, this formulation is only valid when the continuous stiffness measurement mode is employed. For other conditions of indentation, different contact area functions, which take into account the effective truncation length or the radius of the rounded indentertip, as well as some fitting parameters, have been proposed. However, most of these functions require a calibration procedure due to the presence of such parameters. To avoid such a calibration, in the present communication a contact area function only related to the truncation length representative of the indenter tip defect, which can be previously estimated with high resolution microscopy, has been proposed. This model allows the determination of consistent indentation data from indenter displacements of only few nanometers indepth. When this proposed contact area function is applied to the mechanical characterization of a TiHfCN film of 2.6 μm in thickness deposited onto a tool steel substrate, the direct determination of the hardness and elastic modulus of the film leads to values of 35.5±2 GPa and 490±50 GPa, respectively. Wed, 01 Jan 2014 00:00:00 GMT http://hdl.handle.net/10985/8559 2014-01-01T00:00:00Z CHICOT, Didier YETNA N'JOCK, M. PUCHI-CABRERA, Eli-Saul IOST, Alain STAIA, M.H. LOUIS, G. BOUSCARRAT, G. AUMAITRE, R. In nanoindentation, especially at very low indenter displacements, the indenter/material contact area must be defined in the best possible way in order to accurately determine the mechanical properties of the material. One of the best methodologies for the computation of the contact area has been proposed by Oliver and Pharr [W.C.Oliver, G.M.Pharr, J.Mater. Res. 7 (1992) 1564], which involves a complex phenomenological area function. Unfortunately, this formulation is only valid when the continuous stiffness measurement mode is employed. For other conditions of indentation, different contact area functions, which take into account the effective truncation length or the radius of the rounded indentertip, as well as some fitting parameters, have been proposed. However, most of these functions require a calibration procedure due to the presence of such parameters. To avoid such a calibration, in the present communication a contact area function only related to the truncation length representative of the indenter tip defect, which can be previously estimated with high resolution microscopy, has been proposed. This model allows the determination of consistent indentation data from indenter displacements of only few nanometers indepth. When this proposed contact area function is applied to the mechanical characterization of a TiHfCN film of 2.6 μm in thickness deposited onto a tool steel substrate, the direct determination of the hardness and elastic modulus of the film leads to values of 35.5±2 GPa and 490±50 GPa, respectively. http://hdl.handle.net/10985/8662 Analysis of indentation size effect in copper and its alloys CHICOT, Didier; PUCHI-CABRERA, Eli-Saul; IOST, Alain; STAIA, M.H; DECOOPMAN, Xavier; ROUDET, F.; LOUIS, G. For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8662 2013-01-01T00:00:00Z CHICOT, Didier PUCHI-CABRERA, Eli-Saul IOST, Alain STAIA, M.H DECOOPMAN, Xavier ROUDET, F. LOUIS, G. For describing the indentation size effect (ISE), numerous models, which relate the load or hardness to the indent dimensions, have been proposed. Unfortunately, it is still difficult to associate the different parameters involved in such relationships with physical or mechanical properties of the material. This is an unsolved problem since the ISE can be associated with various causes such as workhardening, roughness, piling-up, sinking-in, indenter tip geometry, surface energy, varying composition and crystal anisotropy. For interpreting the change in hardness with indent size, an original approach is proposed on the basis of composite hardness modelling together with the use of a simple model, which allows the determination of the hardness–depth profile. Applied to copper and copper alloys, it is shown that it is possible to determine the maximum hardness value reached at the outer surface of the material and the distance over which both the ISE and the workhardening take place. http://hdl.handle.net/10985/8554 An analysis of the elastic properties of a porous aluminium oxide film by means of indentation techniques HEMMOUCHE, L.; CHICOT, Didier; AMROUCHE, A.; IOST, Alain; BELOUCHRANI, M.A.; DECOOPMAN, Xavier; LOUIS, G.; PUCHI-CABRERA, Eli-Saul The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performe data nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represen the elastic modulus variation. Tue, 01 Jan 2013 00:00:00 GMT http://hdl.handle.net/10985/8554 2013-01-01T00:00:00Z HEMMOUCHE, L. CHICOT, Didier AMROUCHE, A. IOST, Alain BELOUCHRANI, M.A. DECOOPMAN, Xavier LOUIS, G. PUCHI-CABRERA, Eli-Saul The elastic modulus of thin films can be directly determined by instrumented indentation when the indenter penetration does not exceed a fraction of the film thickness, depending on the mechanical properties of both film and substrate. When it is not possible, application of models for separating the contribution of the substrate is necessary. In this work, the robustness of several models is analyzed in the case of the elastic modulus determination of a porous aluminium oxide film produced by anodization of an aluminium alloy. Instrumented indentation tests employing a Berkovich indenter were performe data nanometric scale, which allowed a direct determination of the film elastic modulus, whose value was found to be approximately 11 GPa. However, at a micrometric scale the elastic modulus tends toward the value corresponding to the substrate, of approximately 73 GPa. The objective of the present work is to apply different models for testing their consistency over the complete set of indentation data obtained from both classical tests in microindentation and the continuous stiffness measurement mode in nanoindentation. This approach shows the continuity between the two scales of measurement thus allowing a better representation of the elastic modulus variation between two limits corresponding to the substrate and film elastic moduli. Gao's function proved to be the best to represen the elastic modulus variation.