Experimental-Theoretical Method for Assessing the Stiffness and Adhesion of the Coating on a Spherical Substrate

Known methods and approaches are ineffective or not applicable at all in the study of mechanical characteristics and adhesion of coatings of complex structure, initially formed on non-planar surfaces. A device has been developed that includes fragments of spherical substrates with rings for mounting along the contour, a pressure source of the working medium with a pressure gauge, a line with a valve for supplying the working medium, a measuring complex and a line for etching the working medium. In a fragment of a spherical substrate there is a small diameter hole, in the area of which a cover is formed according to a given technology. The working medium is fed through a small hole in the tray. A segment of the coating detached from the substrate forms a dome in the form of an ellipsoid fragment. A numerical model of deformation of a coating fragment in the form of a spherical segment with a complex contour is being developed using well-known software complexes. At each step of loading by the “targeting” method, varying the modulus of elasticity and the Poisson’s ratio, we approach the parameters of the experimental dome and determine the actual mechanical and stiffness properties of the coating under study. We calculate the normal separation forces through the radial forces determined by the current numerical model, and then determine the coupling stresses. The developed experimental-theoretical method is an effective tool for evaluating the mechanical properties and stiffness of coatings of complex structure, as well as the adhesion of the coating to a spherical substrate.