Some experiments on the microindentation of digital audio tape

The durability of digital audio tape is a function of the elastic and plastic properties of the magnetic layer and substrate. In this work a micro-indentation method has been used to estimate these properties. The loading part of the compliance curve (load against indentor penetration) is analysed to obtain magnetic layer hardness. The unloading part is used to determine the reduced elastic modulus. Indentations at various depths have been recorded and an extrapolation technique used to predict layer properties. Rate dependence of the magnetic layer has been studied through constant loading rate tests. Results are presented isochronally, to indicate any viscous elastic–plastic non-linearities.