Understanding Acoustic Emission Testing- Reading 1 Part B-A

9.0 AE Barkhausen Techniques
The Barkhausen effect
The Barkhausen effect refers to the sudden
change in size of ferromagnetic domains
that occur during magnetization or
demagnetization. During magnetization,
favorably oriented domains develop at the
cost of less favorably oriented domains.
These two factors result in minute jumps of
magnetization when a ferromagnetic
sample (e.g. iron) is exposed to an
increasing magnetic field (see figure).
Domain wall motion itself is determined by
many factors like microstructure, grain
boundaries, inclusions, and stress and
strain. By the same token, the Barkhausen
effect is too a function of stress and strain.
Charlie Chong/ Fion Zhang