Dislocations and Lattice Strain Fields
In materials science parlance, dislocations are defined as line defects in a material's crystal structure. The bonds surrounding the dislocation are already elastically strained by the defect compared to the bonds between the constituents of the regular crystal lattice. Therefore, these bonds break at relatively lower stresses, leading to plastic deformation.
The strained bonds around a dislocation are characterized by lattice strain fields. For example, there are compressively strained bonds directly next to an edge dislocation and tensilely strained bonds beyond the end of an edge dislocation. These form compressive strain fields and tensile strain fields, respectively. Strain fields are analogous to electric fields in certain ways. Specifically, the strain fields of dislocations obey similar laws of attraction and repulsion; in order to reduce overall strain, compressive strains are attracted to tensile strains, and vice versa.
The visible (macroscopic) results of plastic deformation are the result of microscopic dislocation motion. For example, the stretching of a steel rod in a tensile tester is accommodated through dislocation motion on the atomic scale.
Read more about this topic: Work Hardening, Theory
Famous quotes containing the words dislocations and, dislocations, strain and/or fields:
“Imagination of my kind is most caught, most fired, most worked upon by the unfamiliar: I have thriven ... on the changes and chances, the dislocations and ... contrasts which have made up so much of my life.”
—Elizabeth Bowen (1899–1973)
“Imagination of my kind is most caught, most fired, most worked upon by the unfamiliar: I have thriven ... on the changes and chances, the dislocations and ... contrasts which have made up so much of my life.”
—Elizabeth Bowen (1899–1973)
“You are all alike, you respectable people. You can’t tell me the bursting strain of a ten-inch gun, which is a very simple matter; but you all think you can tell me the bursting strain of a man under temptation. You daren’t handle high explosives; but you’re all ready to handle honesty and truth and justice and the whole duty of man, and kill one another at that game. What a country! What a world!”
—George Bernard Shaw (1856–1950)
“O do not grieve
for a torn earth
barren fields burnt forests
cracked riven volcano-broken
hill-slopes islands shrunken
mountains lost.”
—Hilda Doolittle (1886–1961)