Indentation size effect in metallic materials: Correcting for the size of the plastic zone

A correction method is proposed for the Nix/Gao model of the indentation size effect, assuming that the geometrically necessary dislocations are stored within the plastically deformed volume, whose radius is given, depending on the material, by a factor times the contact radius. Using this volume for calculating the depth dependence of hardness and the characteristic indentation length scale h* a good agreement with experiments is found for many metallic materials.