The effect of small-amplitude load oscillations on the nanocontact characteristics of materials in nanoindentation

A continuous stiffness measurement method allowing one to obtain physical-mechamical characteristics of materials in the process of indentation during gradually increasing loading has been scrutinized. The limits of applicability of this approach depend on the testing conditions at which the additional smallamplitude oscillations exert no influence on the mechanics, kinetics, and plastic strain of material being in contact with the indenter. As is shown by taking as examples specimens with amorphous structure, and fcc and bcc lattices, various techniques for determining the nanocontact characteristics of materials are different by their sensitivity to small-amplitude load oscillations. The oscillation amplitudes and the indentation depth ranges where one can neglect the oscillation effects have been evaluated. The impacts of the oscillations on the behavior of the contact (local) characteristics of the studied materials in supercritical modes have been established.