Nanoindentation nowadays is a standard method for the mechanical characterization of thin films and small volumes of material. One of the most meaningful parameters determined in nanoindentation experiments and simulations is the hardness of the tested material. For its determination, the knowledge of the exact value of the projected area in contact between the indenter and the specimen is essential. Inaccurate results for the projected area will result in noticeable errors in hardness. The determination of this area in finite element (FE) nanoindentation simulations is challenging because it cannot be determined directly and phenomena like pile-up and geometric imperfections of the indenter have to be considered. Hence, a new method, namely the triangulation method has been developed. It provides a reliable way to determine the projected area in FE-simulations, even under the occurrence of material pile-up. It is based on the nodes in contact between the indenter and the specimen as well as on the coordinates of the nodes. With this information, a Delaunay triangulation and Alpha shapes can be used to calculate the projected area. The triangulation method is compared to two established methods, one following the Oliver-Pharr analysis and the other one based on the computed true area in contact between specimen and indenter. The three methods are applied to results from an elastic-plastic FE simulation. Bland-Altman plots are used to compare the results of the three methods and to validate the triangulation method.
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