Chapter 4, Problem 4.30P

Interpretation Introduction

Interpretation:

There are two dislocations A and B in the crystal. On applying a shear stress, the effect on the dislocations A and B needs to be explained.

Concept Introduction:

Shear stress is a tangential force which leads to the dislocation or slip of atomic structure. Dislocations are types of defects in the crystal. The two basic types of dislocations are edge and screw dislocations.

Edge dislocation is easy to see in a lattice as an extra half-plane of atoms. Since, the defective points are produced due to dislocation in the line, this is called a line defect. The line runs along the extra half-plane at its top. The distortion is seen in the inter-atomic bonds near the dislocation line.

As compared to the edge dislocation, the screw dislocation is hard to visualize. It also results from shear stress, but the movement of defect line is perpendicular to the stress direction and replacement of metal. Which is parallel in the case of edge distortion.