Necking

Quick
Necking is local deformation of a component. Necking begins at the tensile point, or ultimate stress point.
The neck is the portion of the specimen where necking occurs.


Details

After a certain maximum value of a load, P, has been reached, the area of the middle portion of a specimen may begin to decrease, because of local instability. This phenomenon is known as necking. Necking is commonly associated with ductile materials.



The above image shows a test specimen, when of a certain kind of material, and experienced under a great enough load, experiences necking.
The portion where necking occurs may be called the neck of the specimen.



The above figure shows the necking region in a stress-strain diagram for a ductile material.

Certain metals and plastics can experience necking.

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