It is well-known that surface tilt results in an overestimation of hardness and modulus, due to an underestimated contact area which—resulting in a systematic error in the measured properties.
This paper focuses on improving the contact area determination for nanoindentation of non-ideal samples, specifically samples with low tilt. This work builds on previous literature by adapting an easy-to-use methodology that accounts for the fact that pyramidal probes are not axi-symmetric and that the direction of tilt is as important as the amount of tilt.
This study reports a geometric model that utilized SPM measurements of the side lengths to determine the correction factor directly from an image of the residual indent. This means that there is no required a priori knowledge or measurement of the surface tilt or tilt orientation with respect to pyramid edge or face.
As a result, two contour plots, one for Berkovich and the other for cube corner, were created and provided in this paper. With these contour plots, geometric area correction factors can be directly read for a triangular pyramid probe.
This model is successfully validated using a Bruker-Hysitron (Minneapolis, Minnesota, USA) TriboIndenter equipped with a Berkovich probe on PMMA (poly(methyl metacrylated)) with surface tilts up to 6°.
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FEATURED BRUKER TECHNOLOGY:
Berkovich Nanoindentation, Elastic Properties, Hardness, Nanoindentation, Surface Tilt