For each type of edge, screw, and mixed dislocations, describe briefly the relationship between the direction of the applied shear stress and the direction of dislocation line motion.

A full detail of the edge and screw dislocation and motion is attached in a picture format, attached here.

Explanation:

Edge and Screw Dislocations

• In an edge dislocation, localized lattice distortion exists along the

end of an extra half-plane of atoms.

• A screw dislocation results from shear distortion.

• Many dislocations in crystalline materials have both edge and

screws components; these are mixed dislocations.

• An edge dislocation moves in response to a shear

stress applied in a direction perpendicular to its line.

• Extra half-plane at A is forced to the right; this

pushes the top halves of planes B, C, D in the same

direction.

• By discrete steps, the extra 1/2-plane moves from L

to R by successive breaking of bonds and shifting of

upper 1/2-planes.

• A step forms on the surface of the crystal as the

extra 1/2-plane exits.

Dislocation Motion

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