Reverse analysis in depth-sensing indentation for evaluation of the Young's modulus of thin films

Abstract

This paper presents an approach to reverse analysis in depth-sensing indentation of composite film/substrate materials, which makes use of numerical simulation. This methodology allows the results of experimental hardness tests, acquired with pyramidal indenter geometry, to be used to determine the Young's modulus of thin film materials. Forward and reverse analyses were performing using three-dimensional numerical simulations of pyramidal and flat punch indentation tests to determine the Young's modulus of the thin films. The pyramidal indenter used in the numerical simulations takes into account the presence of the most common imperfection of the tip, so-called offset. The contact friction between the Vickers indenter and the deformable body is also considered. The forward analysis uses fictitious composite materials with different relationships between the values of the Young's modulus of the film and substrate. The proposed reverse analysis procedure provides a unique value for the film's Young's modulus. Depending on material properties, the value of the Young's modulus of the film can be more or less sensitive to the scatter of the experimental results obtained using the depth-sensing equipment. The validity of the proposed reverse analysis method is checked using four real cases of composite materials.

Acknowledgements

The authors are grateful to the Portuguese Foundation for Science and Technology (FCT) who financially supported this work through the Program POCI 2010 (Portuguese Government and FEDER). One of the authors, N.A. Sakharova, was supported by a grant for scientific research from the Portuguese Science and Technology Foundation. This support is gratefully acknowledged.