Thermal drift in room temperature nanoindentation experiments: Measurement and correction

Nanoindentation is widely used for characterizing mechanical properties of materials at small length scales. Thermal drift effects during indentation are well-known, and are typically corrected using a linear relationship between displacement and time. However, this method has serious drawbacks for measuring thermal drift for long duration experiments even at room temperature. We show that for experiments in displacement control (DC) mode, conventional methods to measure thermal drift are inaccurate. Changes in value due to thermal drift occur in load data, not in displacement data since displacement is controlled by transducer in DC experiments. In addition, we find that thermal drift rate may not be constant even for 100 s duration experiments. Drift correction methods that require post-monitoring of displacement lead to errors since unloading behavior is influenced by elastic response of the sample being tested. We propose a novel scheme that involves prior drift monitoring, which alleviates all problems.