In summary, necking occurs during tensile testing of ductile materials due to the limiting uniform elongation and ultimate tensile strength. This is related to the conservation of mass and volume, observed in the Poisson effect, and the significant shearing in the necking area. The formation of necks is caused by the formation of micro-voids during plastic flow, which then coalesce to form micro-cracks and ultimately cause fracture. Overall, voids play a crucial role in the necking phenomenon.
#1
pukb
94
1
Why does necking occur during tensile testing of ductile materials?
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.
#3
MalliCk
33
0
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.