NATURE OF MATERIALS - Materials for Civil and Construction Engineers - page 65

FIGURE 2.10 Atomic packing at
a line defect. (© Pearson Education,
Inc. Used by permission.)

dislocation are in tension. As a result, the atoms are not at their natural
spacing, so the bonds of these atoms are not at the point of minimum
energy, as shown in Figure 2.2. Thus, when a shear stress is applied to this
location, there will be a tendency for the atoms to slip in a progressive man-
ner from position (a) to (b) to (c), as shown in Figure 2.11 (Flinn and Trojan
1986; Budinski 1996).
Volume defects are flaws in the manufactured material; they will not be
discussed further. Area defects are discussed next.

■ 2.2.3 Grain Structure

The structure of metals has been described in terms of the unit cell or the
repeated crystalline structure. However, equally important to the behavior of

(a) (b) (c)

FIGURE 2.11 Plastic deformation involving movement of atoms along a slip

plane.