Comparison of calibration methods for nano-indentation testing machines

To deal with innovative productions and advanced materials, technological surface characterisation is becoming crucial to qualify components and optimise processes. Instrumented Indentation Test (IIT) is an effective method for materials mechanical characterisation enabling bulk to local characterisation by analysing the force-displacement curve resulting from the application of a loading/unloading indentation cycle. To guarantee accuracy, ISO 14577-2 defines procedures to calibrate testing machines. In particular, iterative methods that do not require the indenter area function to be known a-priori, thus avoiding the need of high resolution microscopes, are exploited for calibrating frame compliance and indenter area function. This work, basing on a Monte Carlo approach for evaluating calibration uncertainty, discusses the results of the comparison of these methods in the nano-range. Standards shortcomings due to effect of calibration materials and algorithms are highlighted as well.