A tensile-film-cracking model for evaluating interfacial shear strength of elastic film on ductile substrate

The stress distribution associated with the film cracking model originally proposed by Agrawal and Raj is further investigated through the use of the finite element analysis (FEA) technique. The result of the FEA analysis indicates that the interfacial shear stress can be approximated by a quarter segment of an elliptical function, rather than by a sine function of a full wavelength as employed in the original model. A modified model related to the maximum interfacial shear stress is thus proposed. The validity of the new model has been tested in a TiN coating–304 stainless steel system. It is demonstrated that the interfacial shear strength evaluated through the new model is of the same order of magnitude as that of the yield shear strength of the substrate.