The dynamics of frequency-specific, depth-sensing indentation testing

Depth-sensing indentation involves applying a specific force-time history on a rigid indenter while continuously monitoring the displacement of the indenter into the surface. Frequency specific depth-sensing indentation testing entails adding a small harmonic force on the indenter and measuring the harmonic response of the indenter at the excitation frequency. While often taken for granted, understanding the dynamics behind these frequency specific measurements is of vital importance in the determination of quantitative mechanical properties. This paper will focus on the dynamics of a variety of depth-sensing indentation systems and how these dynamics affect such parameters as detecting the point of surface contact, environmental sensitivity, dynamic frequency range, and the range over which contact stiffnesses and moduli can be accurately measured.