Dislocations edge, defined

Fig. 3.47 This force is acting in the negative y direction, because tensile stress induces the negative climb of a dislocation. Note that the width at the lower edge of the curve is less by b than at the upper edge, since a dislocation is defined by the extra half-plane [14]...

Dislocations are line defects. They bound slipped areas in a crystal and their motion produces plastic deformation. They are characterized by two geometrical parameters 1) the elementary slip displacement vector b (Burgers vector) and 2) the unit vector that defines the direction of the dislocation line at some point in the crystal, s. Figures 3-1 and 3-2 show the two limiting cases of a dislocation. If b is perpendicular to s, the dislocation is named an edge dislocation. The screw dislocation has b parallel to v. Often one Finds mixed dislocations. Dislocation lines close upon themselves or they end at inner or outer surfaces of a solid. 

Line defects in crystals such as screw or edge dislocations are quite common in solid substances. The typical length of all dislocation in 1 m3 of annealed material amounts to 1010 m (10 km in 1 cm3). The so-called dislocation density is defined as ... 

The values in Figure 13.13 for edge and screw dislocations define upper and lower bounds for As the average contrast factors for the limiting cases of... 

Recall from our discussion in chap. 2 that the solution of elasticity problems of the two-dimensional variety presented by the edge dislocation is often amenable to a treatment in terms of the Airy stress function. Consultation of Hirth and Lothe (1992), for example, reveals a well-defined prescription for determining the Airy stress function. The outcome of this analysis is the recogiution that the stresses in the case of an edge dislocation are given by... 

Fig. 3.25 Line DC defines an edge dislocation, which is the termination of an extra plane in a cubic crystal. A missing atom is also shown which is a vacancy [14]...

As indicated in Sect. 3.3.1, dislocations are line defects. The two basic types of dislocations are the edge and screw dislocations. A schematic three-dimensional (3D) illustration of an edge dislocation appears in Fig. 3.25. A (100) plane of Fig. 3.25 in a simple cubic crystal is illustrated schematically in Fig. 3.28. This illustration will help to define the Burgers vector later on. Figure 3.29 is a schematic view of edge and screw dislocations. 

Fig. 3.53 The jog, PP, and the screw dislocation line, AP PB, after intersection. This jog has an edge character and its glide plane (i.e., where the jog can glide) is defined by the shaded area. Movement of the screw dislocation to A B can occur only by climb [14]...

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