Indenter tip radius and load frame compliance calibration using nanoindentation loading curves

The finite-element method has been used to simulate the indentation process of a variety of isotropic elastic-plastic materials indented by a rigid conical indenter with a perfectly sharp tip and round tips of various radii. Analyses of the obtained loading curves showed that the load frame compliance Cf of the nanoindentation instrument and the tip roundness r of the indenter can be determined from the loading curve. In a real indentation experiment, the obtained raw load-depth data during the loading stage can be described by the second-order polynomial dependence of depth on the square root of load, from which the Cf and r values are determined. An experimental procedure has thus been proposed for Cf and r calibration using the loading curves of a hard and isotropic material. Nanoindentation experiments on fused silica demonstrate the reliability of the proposed technique for accurate and quick Cf and r calibration.