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Why does necking occur during tensile testing of ductile materials?

  1. Apr 13, 2012 #1
    Why does necking occur during tensile testing of ductile materials?
     
  2. jcsd
  3. Apr 13, 2012 #2

    Astronuc

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    Re: Necking

    Necking coincides with the limiting uniform elongation, which corresponds with the ultimate tensile strength.

    The reduction in (cross-sectional) area is related to conservation of mass (and volume), which is observed in the Poisson effect. One observes a significant amount of shearing in the necking area. Basically it is a region of local instability in the material.
     
  4. Apr 14, 2012 #3
    Formation of necks is mainly due to the formation of micro-voids, that form during the plastic flow of metals/alloys under tension. So, when a micro-void is formed atomic layers slide around them. These micro-voids coalesce to form micro-cracks (Stress Raisers) which causes fracture.
    Basically voids are responsible for the necking phenomenon.

    Hope this helps you !
     
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