The present paper describes an application of Hertzian indentation with rheological models as a method for determining the fracture of any multi-layered brittle coating. The advantage of the method revealed here is that the only quantity to be measured is a deformation or a fracture load. Use of a refined stress intensity factor formulation for surface-breaking cracks in steep stress gradients has enabled accurate estimates to be made of the minimum loads necessary to propagate cracks by Hertzian indentation. At present the analysis only applies for the case where the sphere and the substrate are made of similar materials. However, the analysis is comprehensive in that it can be applied to sphere/substrate systems with any value of Poisson’s ratio, elastic, plastic and viscous properties of materials that may be included in appropriate rheological models for study a strain-deformation state. By measuring this minimum load (and that is the only quantity that must be measured) an accurate estimate of fracture may easily be made with application of rheological modeling. Two further points are worthy of note. Because the only quantity that must be measured is a fracture load, it is possible that this method of determining fracture can be automated with equipment and software. Also, the existence of an absolute minimum fracture load, for a given sphere size, suggests that the Hertzian indentation test could find use as a localized proof-test.

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