Mapping of the plastic zone under nanoindentation imprints : toward a better ductile to brittle transition insight in oxide glasses
Abstract
In order to study the regime of nanoindentation for which
plasticity (shear flow and densification) is the only responsible for the
creation of the residual imprint (i.e. no crack).We have developed a
technique allowing for the 3-dimensional probing of the plastic zone, with a
nanometer scale resolution underneath nanoindentation imprints.
Nonetheless this regime is quite difficult to study experimentally as it requires
the application of ultra-low indentation loads (below 50 mN) in order to
minimize as much as possible the occurrence of cracks. This leads to a
plastic zone size of the order of tens to hundreds of nanometers, which
makes conventional methods such as Micro Raman or Brillouin
Spectroscopies inappropriate to study this zone. The experimental approach
is nonetheless necessary for the validation of the constitutive law
implemented in numerical simulations.This method based on AFM and image
3D image treatment is sensitive to the structural modifications in the glassy
network resulting from the densification and allows for the 3-dimensional
reconstruction of the plastic domain. We will present the robustness of the
developed method as well as experimental results such as the effect of load,
loading rate. This method is also very promising for studying the first steps of
crack nucleation under sharp contact.