Details

Autor(en) / Beteiligte

• Pathak, Siddhartha
• Riesterer, Jessica L.
• Kalidindi, Surya R.
• Michler, Johann

Titel

Understanding pop-ins in spherical nanoindentation

Ist Teil von

• Applied physics letters, 2014-10, Vol.105 (16)

Ort / Verlag

Melville: American Institute of Physics

Erscheinungsjahr

2014

Quelle

American Institute of Physics

Beschreibungen/Notizen

• Pop-ins, or sudden displacement-bursts at constant load in a nanoindentation test, are typically attributed to the difficulty of setting up potent dislocation sources in the very small indentation zones in these experiments. Such displacement (and strain) bursts would intuitively indicate a sharp drop in stress during the pop-in event itself. However, spherical indentation stress-strain curves routinely exhibit a high and stable indentation stress value during the pop-in, and the indentation stresses decrease only after a further finite amount of additional indentation displacement has been applied. In order to understand this discrepancy, we utilize a combination of interrupted spherical indentation tests along with depth profiling of the residual indentation surfaces using in-situ atomic force microscopy (AFM) to study pop-ins. The AFM surface profile maps show that there is an asymmetric profile change over a limited region around the indentation contact area for a single pop-in; the asymmetry disappears upon further loading beyond the pop-in. A plausible sequence of physical processes (related to metal plasticity) occurring underneath the indenter during and immediately after the occurrence of the pop-in is proposed to explain these observations.