DEFECTS IN METALS AND SIMULATION OF MECHANICAL ...

Fig. 2-9 shows that with a higher stiffness (k=1000 eV/ Ǻ 2 and above) of the indenter is
very close to the Hertzian fit in terms of force and displacement values, which is a proof that the
system during nanoindentation behaves as it s supposed to behave during experimental
nanoindentation.
In summary, the effect of vacancies on the yield load in nanoindentation was studied by
molecular dynamics simulations. The results indicate that the presence of vacancies lowers the
yield load, and a higher concentration will cause a higher deviation from the yield point with no
vacancies following a weak power law relationship. During nanoindentation we can observe that
the number of vacancies is going down as the indenter depth is higher.
Dislocations begin to form at the yield load and after this point the model behaves plastically.
The vacancies are not required to be present at the regions of highest imposed shear stresses to
impact the nucleation stress, and as such may be influencing the stress field in the solid as well
as participating directly in mechanisms that require additional time or temperature to activate a
source.
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