Three-point bending (3PB) and indentation tests are often employed for calibrating mechanical models of homogeneous materials. Mechanical calibration means here identification of parameters which are contained in constitutive elastic-plastic and fracture models and turn out to be not directly measurable by traditional elementary tests. Either semi-empirical formulae or inverse analysis can be used for such calibration. Inverse analysis based on suitable finite element simulations of the test allows to exploit wider sets of experimental data and to increase the number of estimated parameters and estimation accuracy.
In the two calibration methods proposed and discussed in this paper, traditional experimental information consisting of loading-unloading curves (reaction force versus imposed displacement) are supplemented by further data: in the 3PB tests, by displacements measured through interferometric optical means on the lateral surfaces of the specimen like in [
]; in instrumented indentations, by the mapping of residual imprints as in [
]. The estimation of the mechanical properties dealt with herein concerns metal-ceramic functionally graded materials (FGMs), the mechanical behavior of which is described by modified mixture laws [
The indentation technique is applied to a thin FGM coating on ductile metallic substrate, in order to assess the volume fraction distribution of the components across the thickness of the FGM layer. The purpose is to establish the effectiveness and robustness arising from the use of imprint mapping data in the identification process.
Parameter estimation by 3PB tests is applied to FGM layers of relatively large thickness (few millimeters of magnitude order) and concerns the phase distribution transversal to the specimen (which exhibits vertical symmetry) and the fracture properties of the components, namely tensile strength and fracture energy, consistently with a simple cohesive crack model.