An inverse analysis approach based on a POD direct model for the mechanical characterization of metallic materials

Indentation tests are frequently employed to determine the mechanical properties of materials and are particularly suitable when dealing with small components due to their "quasi-non-destructiveness". During an indentation test, the material is subjected to a triaxial stress state and, because of this, the mechanical properties cannot be inferred directly from the experiments. In these cases, suitable procedures must be implemented to derive them and, among the different alternatives available in the literature, the inverse analysis approach has been extensively studied and applied to a wide range of materials and systems. When the inverse analysis procedure relies on the use of a time-consuming finite element model for the modelling of an experimental test, the results are accurate yet computationally demanding. In the present paper, a numerically efficient approach was implemented, which relied on the use of an 'a priori' finite element model reduction procedure. This consists of a Proper Orthogonal Decomposition (POD) model that simulates the response of the material when subjected to an indentation test. The experimental data used in this study as input to the inverse analysis approach consist of both indentation curves and pile-up markings observed at the end of the indentation in the samples. Independent tensile tests were carried out on samples of aluminium alloys AA 6061-O and AA 7075-O. These experimental results were used for the validation of the proposed numerical approach. These results highlighted the accuracy and efficiency of the proposed procedure.