The sharpness of a Berkovich indenter

Precise calibration of the indenter shape is an important procedure in nanoindentation analysis since the indenter geometry enters directly into the most common methods of data analysis in this type of testing. Not only is the geometry required to be known with some precision, but also the sharpness of the tip, especially in the case of pyramidal indenters, is important for the use of indenters for testing hardness in thin film specimens—the most common application of nanoindentation. In this paper, a method of determining the area function and tip radius for a Berkovich indenter is described. It is shown that the tip radius estimated from the area function data is in reasonable agreement with a direct measurement using a calibrated atomic force microscope. It is shown that subjective decisions about tip radius may lead to unjustified rejection of a tip for hardness measurement. A new criterion for tip quality is presented in terms of tip radius and specimen material properties.