FIFTH CANADIAN CONFERENCE ON NONDESTRUCTIVE ... - IAEA

EXTENSION
CONTRACTION
- 87 -
COMPRESSED
FIELD (H)
UNSTRESSED
TENSIONED
Figure 5: Magnetostriction is the fractional change in length, the strain of
a ferromagnetic material when magnetised. Initially iron expands
on magnetisation but at higher fields it begins to contract, as
shown. The effect is also stress dependent. Compression tends to
enhance the region of expansion, tension to reduce it. The inverse
effect, the change of magnetisation with stress variation, is the
magnetomechanical effect which was expected to have a reciprocal
behaviour.