Magnetic Damping in Conducting Solids
Magnetic Damping of Vibrating
Conducting Solids
COMSOL
Introduction
When a conductive solid material moves through a static magnetic field, an eddy current
density is induced
That induced eddy current density interacts with the static magnetic field and the result is
a Lorentz force back on the solid that counteracts the motion
Therefore, a conducting solid that is vibrating in a static magnetic field experiences a
structural damping
Model Definition
This example computes the
damping effect when a cantilever
beam is harmonically excited
across a range of frequencies and
placed in a strong magnetic field
Assumptions made:
‒
the relative magnitude of the
structural displacements are small
‒
the material has isotropic and linear
properties
A vibrating beam next to a current carrying wire experiences magnetic
damping
Model Definition
A vibrating beam next to a current carrying wire experiences magnetic
damping
‒
the damping Lorentz force can be
computed from the static magnetic
field and the motion-induced AC
eddy current density
Model Definition
Second-order effects arising from
the AC magnetic field generated
by the eddy currents are not
included in the computation
The AC magnetic field is also
computed and found to be 2-
3 orders of magnitude smaller
than the DC magnetic field
A vibrating beam next to a current carrying wire experiences magnetic
damping
Model Definition
Solid Mechanics
Results
The figure shows the magnetic
flux density computed for the
structure
The magnetic field around a current carrying wire
Results
The figure displays the magnitude
of the displacement of the tip of
the beam versus excitation
frequency for two different
magnetic field intensities for the
frequency-domain structural
dynamics problem
Displacement of the tip of the beam versus excitation frequency for
differing magnetic field strengths
Results
The figure shows a snapshot of
the induced eddy current
distribution in the beam
The AC current distribution
When a conductive solid moves through a magnetic field, eddy currents are induced, creating an interaction that leads to magnetic damping. This phenomenon, known as magnetic damping of vibrating conducting solids, plays a crucial role in various applications and can be analyzed using tools like COMSOL.
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