Indentation and imprint mapping for the identification of constitutive parameters of thin layers on substrate: perfectly bonded interfaces

Indentation tests are at present frequently employed for the identification of material parameters at different scales. The indentation curve provides experimental data for the calibration of mechanical models through traditional semi-empirical formulae or through simulation of the test and inverse analysis. A recently proposed innovative inverse analysis technique combines the traditional indentation test with the mapping of the residual deformations (imprint), thus providing experimental data apt to be used to identify isotropic and anisotropic material parameters in more accurate fashion and in larger number. In this paper, such new methodology is employed for the identification of material properties in film–substrate systems. The film and a significant portion of the underlying bulk material are incorporated in the finite element models built up to simulate the indentation test in finite strain regime. The substrate material properties are considered among the unknown parameters to be identified through inverse analysis, carried out by a batch, deterministic approach, using conventional optimisation algorithms for the minimisation of a suitably defined discrepancy norm. Several numerical examples are discussed in order to test the performance of the proposed methodology in terms of result accuracy and computing effort.