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Integrated Computational Materials Engineering (ICME) for Metals: Using Multiscale Modeling to Invigorate Engineering Design with Science by Mark F. Horstemeyer

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4.3 DISLOCATION MECHANICS BASICS

In this section, we review the basics of dislocations. The presentation is not meant to be exhaustive but enough to provide a basis for the reader. For a more elaborate discussion of dislocation mechanics, the reader is advised to consult with the books by Hull and Bacon [12] and Weertman and Weertman [13] for a comprehensive introductory presentation and the book by Hirth and Lothe [14] for a more advanced presentation.

4.3.1 Geometrical Attributes of Dislocations

A dislocation is a crystal line defect whose motion and interactions with other dislocations and crystal defects govern the plastic behavior of metals. As a dislocation glides, it causes slip, and hence its line defines the boundary between the material that slipped and that which did not. Figure 4.2 shows a simple thought process (referred to as the slice–shift–rejoin process) to illustrate the association between slip and dislocation. Figure 4.2a shows a perfect simple cubic crystal with an imaginary cut ABCD in the x-y plane, which breaks the atomic bonds across the crystal. To deform the crystal permanently, an x-z shear stress can be applied, as in Figure 4.2b, to cause relative sliding (slip) of one atomic spacing b between the two parts of the crystal above and below the cut, followed by the rejoining of the broken atomic bonds. As a result of this process, line AB is now associated with a crystal defect (additional half plane) and separates the slipped and unslipped parts of the ...

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