Fracture of Thin Elastic Films on a Metal Substrate

摘要

A ductile metal substrate with a brittle thin film coating is one of common coating-substrate structures encountered in engineering applications. Fracture behavior of the thin film coating and the coating adhesion are among the major considerations in evaluating the integrity and quality of such coating-substrate systems. A reliable and consistent measurement of these properties is also critical in improving the thin film processing technologies. Based on our recent study of anodic oxide coatings on aluminum alloys, a new methodology has been developed to better measure the fracture property of the thin oxide coating and the interfacial strength of oxide-metal interface. The essential aspects of the methodology including (a) in-situ tensile testing of plastically deforming coated substrate under optical microscope, scanning electron microscope and atomic force microscope and (b) a nonlinear finite element analysis of the coating-substrate system. In this talk, we will detail the theoretical and experimental basis of this new methodology with a particular emphasis on the importance of setting up the proper boundary conditions in finite element method baaed stress analysis of a reduced coating-substrate model.