Practical implications of instrument displacement drift during force-controlled nanoindentation

The accuracy of instrumented indentation data relies heavily on the evaluation of experimental errors such as displacement drift. In spite of its importance, little attention has been given to the magnitude of an acceptable displacement drift rate, its relationship to a given set of test conditions, and how errors manifest themselves in force-displacement data. In this work we explored how drift rates that were acceptable for short-term tests caused artificial "abnormal" behavior that could have been interpreted as a true material response for a longer-term test. A critical review of the drift behavior of the nanoindentation system revealed that a useful metric for screening data quality was the nominal accumulated system drift as a fraction of the maximum penetration depth. Additionally, suggestions for drift management during nanoindentation tests were given.