Spherical impression of thin elastic films on elastic–plastic substrates

The mechanical behavior of thin elastic _lms deposited onto structural alloys plays a critical role in determining _lm durability[ This paper presents analysis of an impression experiment designed to evaluate some of the relevant properties of these _lms[ The modeling provides quantitative strain information which can be used to estimate the fracture toughness of the _lm\ the static friction coe.cient of the surface and the constitutive behavior of the substrate[ Results are presented for radial and circumferential strain distributions in the _lm relevant to the interpretation of cracking patterns[ Additionally\ load!displacement curves are provided that may be used to evaluate the plastic properties of the substrate[ To facilitate estimates of the _lm cracking strain through correlation with experiments\ the radial strain distributions are presented as functions of impression depth\ yield strain and hardening exponent