Understanding Acoustic Emission Testing- Reading 1 Part B-A

Also, the TRIP steel is particularly useful for side impact protection. The
material deforms and absorbs the energy of the impact. It also becomes very
strong as it hardens, which prevents the side sections from collapsing too
much and protects vehicle occupants from injury.
However, the double TRIP effect does not explain why an alloy with 15-25
manganese content is particularly ductile. This is caused by small faults in the
crystal structure called "stacking faults". Stacking faults can be visualized as a
shift in the grid of atomic planes neatly arranged side by side and one on top
of the other. If an extra stack of two atomic planes is introduced into the lattice
from above, the regular stacking sequences are disturbed and therefore form
a stacking fault. This folding mechanism takes place on a mirror plane,
creating regularly mirrored sections of crystal. Experts refer to this as twinning,
which is what manifests itself externally as extreme ductility.
Charlie Chong/ Fion Zhang
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