Contact area correction for surface tilt in pyramidal nanoindentation

A correction is needed to minimize errors in contact area caused by surface tilt in nanoindentation. Surface tilt decreases the contact area calculated using standard analyses that assume the tested surface is not tilted and thus results in overestimation of hardness and elastic modulus. Both the direction of tilt with respect to the pyramid face and the angle of the pyramidal probe are important when characterizing error caused by surface tilt. Here, a geometric model was used to create contour plots from which the area correction factor can be directly determined using only the ratios of side lengths measured from an image of the triangular nanoindentation impression. Contour plots for Berkovich, cube corner, and two nonstandard pyramidal probe geometries are given. The efficacy of the method was demonstrated in the correction of Berkovich nanoindentation on facets in freshly prepared poly(methyl methacrylate) with surface tilts as high as 6 degrees. Graphic