Title: Detecting in-plane tension induced crystal plasticity transition with nanoindentation,
Abstract: We present experimental data and simulations on the effects of in-plane
tension on nanoindentation hardness and pop-in noise. Nanoindentation
experiments using a Berkovich tip are performed on bulk polycrystaline Al
samples, under tension in a custom 4pt-bending fixture. The hardness displays a
transition, for indentation depths smaller than 10nm, as function of the
in-plane stress at a value consistent with the bulk tensile yield stress.
Displacement bursts appear insensitive to in-plane tension and this transition
disappears for larger indentation depths. Two dimensional discrete dislocation
dynamics simulations confirm that a regime exists where hardness is sensitive
to tension-induced pre-existing dislocations.