DEFECTS IN METALS AND SIMULATION OF MECHANICAL ...

Fig. 2-3: Force displacement curves for indenter velocities of 20 and 100m/s with no
vacancies.
As expected Fig. 2-3 shows that the yield load decreases as the velocity of the indenter decrease,
comparable to what was observed by other investigators [ 25 ] where the yield stress decreased
with a lower strain rate. In addition Te-hua Fang et al. [ 26 ] investigated the atomistic mechanism
of nanoindentation process under various indentation loads and velocities using a diamond tip
penetrating a copper thin film, they found that at higher indentation velocities the Young’s
modulus and hardness increase, which explains the difference in the elastic part shown in Fig. 2-
3 for different indentation velocities in iron.
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