Dislocation

In materials science, a dislocation is a crystallographic defect, or irregularity, within a crystal structure. The presence of dislocations strongly influences many of the properties of materials. The theory was originally developed by Vito Volterra in 1905 but the term 'dislocation' was not coined until later by the late Professor Sir Frederick Charles Frank of the Physics Department at the University of Bristol. Some types of dislocations can be visualized as being caused by the termination of a plane of atoms in the middle of a crystal. In such a case, the surrounding planes are not straight, but instead bend around the edge of the terminating plane so that the crystal structure is perfectly ordered on either side. The analogy with a stack of paper is apt: if a half a piece of paper is inserted in a stack of paper, the defect in the stack is only noticeable at the edge of the half sheet.

There are two primary types: edge dislocations and screw dislocations. Mixed dislocations are intermediate between these.

Mathematically, dislocations are a type of topological defect, sometimes called a soliton. The mathematical theory explains why dislocations behave as stable particles: they can be moved about, but maintain their identity as they move. Two dislocations of opposite orientation, when brought together, can cancel each other (this is the process of annihilation), but a single dislocation typically cannot "disappear" on its own.

Read more about Dislocation:  Dislocation Geometry, Observation of Dislocations, Sources of Dislocations, Dislocations, Slip and Plasticity, Dislocation Climb

Other articles related to "dislocations, dislocation":

Lomer-Cottrell Junction
... junction is a particular configuration of dislocations ... When two perfect dislocations along a slip plane, each perfect dislocation can split into two Shockley partial dislocations a leading dislocation and a trailing dislocation ... When the two leading Shockley partials combine, they form a separate dislocation with a burgers vector that is not in the slip plane ...
Dislocation Climb
... Dislocations can slip in planes containing both the dislocation and the Burgers Vector ... For a screw dislocation, the dislocation and the Burgers vector are parallel, so the dislocation may slip in any plane containing the dislocation ... For an edge dislocation, the dislocation and the Burgers vector are perpendicular, so there is only one plane in which the dislocation can slip ...
Charcot Arthropathy - Radiologic Findings
... disease, characterized by acute peri-articular fracture and joint dislocation ... the "6 D's" of hypertrophy are Distended joint Density increase Debris production Dislocation Disorganization Destruction The natural history of the ... joints in the medial left foot, with fracture and dislocation of fragments these are classic findings ...
Types of Pinning Points - Second Phase Precipitates
... of a material creates physical blockades through which a dislocation cannot pass ... The result is that the dislocation must bend (which requires greater energy, or a greater stress to be applied) around the precipitates, which inevitably leaves residual ...
Dislocation Creep
... Dislocation creep is a deformation mechanism in crystalline materials ... Dislocation creep involves the movement of dislocations through the crystal lattice of the material ... Dislocation creep is highly sensitive to the differential stress on the material ...

Famous quotes containing the word dislocation:

    For, as it is dislocation and detachment from the life of God, that makes things ugly, the poet, who re-attaches things to nature and the Whole,—re-attaching even artificial things, and violations of nature, to nature, by a deeper insight,—disposes very easily of the most disagreeable facts.
    Ralph Waldo Emerson (1803–1882)