A Case Study in Dislocations and Plasticity Nanoindentation

An attractive higher-level framework within which to study plasticity during nanoindentation is provided by the dislocation dynamics methods described above. In particular, what makes such calculations especially attractive is the possibility of making a direct comparison between quantities observed experimentally and those computed on the basis of the nucleation and motion of dislocations. In particular, one can hope to evaluate the load-displacement curve as well as the size and shape of the plastic zone beneath the indenter, and possibly the distribution of dislocations of different character. While the 

The subsurface dislocation structures described above can be revealed by electron microscopy as shown in fig. 12.31. Such experiments are suggestive of the physical mechanisms involved in the onset of plasticity and provide the hope of quantifying the crystallography and size of the initial dislocation loops. 

In addition, tests of this type also reveal some of the key effects that emerge once the characteristic dimensions of the problem (i.e. the grain size, the indenter size, etc.) begin to reach into the nanometer range. Indeed, one compelling example of such size effects has been argued for in the context of nanoindentation as seen in fig. 12.32. 

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