| We estimate the "true" hardness value of a thin-film from composite hardness obtained by a conventinol microhardness tester. To separate the substrate and film contributions to the composite hardness, we apply the plastic-zone volume-law-of mixtures theory through the stress analysis of indentation. At this time, the geometrical deformation types are considered: spherical for substrate and cylindrical for film to consider the surface effect When an interface has a strong bonding, namely, no interface delamination occurs during loading, the deformation in the soft substrate is assumed to be restricted by the brittle film on condition that the strains of both film and substrate match at interface. And, in calculating the plastic-zone radii, the virtual pressures which the substrate and film actually support are considered. On the other hand, when an interface is weak, an interface parameter is introduced to reflect the partial debonding at interface during loading, resulting in the partial reease of plastic-zone confinement in the soft substrate. |
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