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The illustrations shows Voltaterras basic idea:
Take a cylinder of a material, cut it along some wall, move the surfaces of the
cut in all ways that - after welding the wall together again - will lead to
different deformation states. |
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There is a limited and rather small number of possible
independent cuts. All other cuts plus some deformation can always be experessed
as a linear superposition of the elementary cuts. |
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Here are the elementary cuts. The first 4 ones correspond to
dilocationes - i.e. a real dislocation produces exactly the kind of
straín field produced by the cut; the last three ones corresponds to
defects (disclinations) that are more elementary than dislocations, but are not
observed in real crystals. They do however, appear in two-dimensional lattices,
e.g. in the flux-line lattice of
superconductors. |
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5.2.2 Stress Field of a Straight Dislocation