Correction factor for contact radius in spherical indentation measurements

A correction factor for applying previous method proposed by Collin et al. (2008) to indentation test with high strain rate is proposed in this paper. While the previous method allowed an accurate determination of the contact radius changes from the unloading stiffness and the elastic properties for a/R ratio lower than 0.25, the correction factor allows application of the method whatever the a/R ratio. It is shown that the proposed method is more accurate than methods using C2 factor depending on plastic properties of the sample. Moreover, the proposed method is the only one to determine the contact radius changes during the unloading process.

► Contact radius is an important data in the study of instrumented indentation.
► A correction factor to a former paper is proposed in this paper.
► Factor increases the accuracy and the field of application of the previous method.