The Effect of the Vertex Angles of Wedged Indenters on Deformation during Nanoindentation
X. W. Hu and Y. S. Ni
Crystals, 7, 380 (2017).

ABSTRACT
In order to study the effect of the angle of wedged indenters during
nanoindentation, indenters with half vertex angles of 60 degrees, 70 degrees and
80 degrees are used for the simulations of nanoindentation on FCC aluminum (Al)
bulk material by the multiscale quasicontinuum method (QC). The
load-displacement responses, the strain energy-displacement responses, and
hardness of Al bulk material are obtained. Besides, atomic configurations for
each loading situation are presented. We analyze the drop points in the
load-displacement responses, which correspond to the changes of microstructure
in the bulk material. From the atom images, the generation of partial
dislocations as well as the nucleation and the emission of perfect dislocations
have been observed with wedged indenters of half vertex angles of 60 degrees and
70 degrees, but not 80 degrees. The stacking faults move beneath the indenter
along the direction [110]. The microstructures of residual displacements are
also discussed. In addition, hardness of the Al bulk material is different in
simulations with wedged indenters of half vertex angles of 60 degrees and 70
degrees, and critical hardness in the simulation with the 70 degrees indenter is
bigger than that with the 60 degrees indenter. The size effect of hardness in
plastic wedged nanoindentation is observed. There are fewer abrupt drops in the
strain energy-displacement response than in the load-displacement response, and
the abrupt drops in strain energy-displacement response reflect the nucleation
of perfect dislocations or extended dislocations rather than partial
dislocations. The wedged indenter with half vertex angle of 70 degrees is
recommended for investigating dislocations during nanoindentation.