Axi-symmetric contact on thin compliant coatings

This paper presents a theory for the indentation of a soft thin coating by a rigid body. The coating is assumed to be bonded to a rigid substrate and to behave linearly elastically. A simplifying approximation enables the stresses within the coating, averaged through its thickness, to be determined for particular indenter profiles. The results are shown to be sensitive to the thickness and compressibility of the coating material. Unlike much previous work, the results can be expressed analytically for certain indenter profiles and have been substantiated by experiment. The theory has many useful applications, in particular for situations where the layer acts as a protective coating and for the accurate, in situ and non-destructive measurement of the elastic modulus of the coating material.