Direct measurement of indentation frame compliance

Accurate determination of frame compliance is an essential component of instrumented micro- and nanoindentation experiments. In load frames of finite stiffness, the load applied via the indenter induces displacement in both the sample and the load frame. Frame compliance must be identified and subtracted from the total indenter displacement to account properly for sample deformation. Current experimental procedures, in which the frame compliance is inferred from the elastic unloading indentation response of a reference sample, are based on several assumptions and simplifications that can propagate significant uncertainty with respect to subsequent analyses of mechanical behavior of the sample. We outline a new procedure that measures the compliance of the load frame, and identify the effects of load, loading direction, and loading rate on the measured compliance, as well as several possible sources of uncertainty in other available methods of frame compliance determination.