Measuring elastic–plastic properties of thin films on elastic–plastic substrates by sharp indentation

A new technique has been proposed to measure the elastic–plastic properties of thin film materials on elastic–plastic substrates from the force–displacement curve of the sharp indentation. With the assistance of the substrate effect, explicit relationships between the indentation parameters and the elastic–plastic properties of film–substrate materials are established through extensive finite element analysis. The forward analysis predicts an indentation response from a given set of elastic–plastic properties of film/substrate systems considering the substrate effect, whereas the reverse analysis seeks to extract film elastic–plastic properties from depth-sensing indentation response with a moderate penetration depth. Numerical indentation tests are carried out to examine the effectiveness of the proposed method. Both nanoindentation and uniaxial tensile tests are also carried out on Ni films coated on mild steel substrates and the good agreement shows that the proposed film indentation technique can be applied in practice.