Influence of sample thickness and experimental device configuration on the spherical indentation of AISI 1095 steel
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d Mauvoisin, Olivier Bartier, and Xavier Hernot L.A.R.M.A.U.R-Indentation, E.A. 42.82, Université de Rennes 1, Campus de Beaulieu, 35402 Rennes Cedex, France
Simon-Serge Sablin
Technocentre Renault, Research Advanced Studies and Materials Engineering (DREAM) – Material Engineering Department (DIMat), 78288 Guyancourt Cedex, France (Received 5 May 2011; accepted 19 July 2011)
Most 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. I. INTRODUCTION
The spherical indentation test data is obtained by continuously measuring the applied load F and penetration depth h of a stiff spherical indenter of radius R in the surface of the tested material. Concerning metallic alloys, recent studies have shown that the data from a single spherical indentation test has the potential to evaluate a unique solution for the Young modulus as well as for the two parameters of the Hollomon hardening law, especially if sufficiently deep normalized penetration h/R is achieved in the case of materials that are difficult to differentiate.1,2 The spherical indentation test has been widely used to evaluate the mechanical properties of bulk materials,3–14 treated surfaces, and coatings15–17 by computer-assisted inverse analysis. Some studies have also considered anisotropic materials and proposed to use the geometry of the residual imprint as additional information for computerassisted inverse analysis.18,19 The main advantages of the indentation test compared, for instance, to the tensile test, are the local probing of mechanical characteristics and the few restrictions on the sample shape and size. However, most of the theoretical and numerical models proposed so far consider infinite a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.247 76
J. Mater. Res., Vol. 27, No. 1, Jan 14, 2012
http://journals.cambridge.org
Downloaded: 26 Apr 2015
sample dimensions compared to the indenter radius, which implies no influence on the indentation response. Few studies on metallic sheets also consider the thickness to be high enough to have no influence.20 Only few studies have considered the influence of sample thickness on indentation response. For example, Yang21 studied the indentation problem o
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