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1
1
(a)
(b)
0.9
0.95
0.8
0.7
0.9
0.6
0.5
0.85
0.4
0.8
0.3
0.2
0.75
0.1
0
0.7
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
RWWSI
RWWSI
Fig. 6.
Relationship between the Rayleigh wave vibration amplitude and the RWWSI.
Rayleigh waves are generated by Lorentz forces (a) due to the dynamic magnetic field
and (b) due to the static magnetic field respectively. The maximum vibration ampli-
tudes are normalized.
4
14
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
(b)
(a)
3
12
2
10
1
8
0
6
-1
4
-2
2
-3
0
-4
-2
-25
-20
-15
-10
-5
0
5
10
15
20
-25
-20
-15
-10
-5
0
5
10
15
20
Y (mm)
Y (mm)
Fig. 7.
(a) Z-direction Lorentz force distributions due to dynamic magnetic field and
(b) Y-direction Lorentz force distributions due to static magnetic field with different
RWWSI
the minimum value when the RWWSI is 0.5. Fig. 6 illustrates that Rayleigh
waves generated by Lorentz force due to the dynamic magnetic field decreases
sharply with the increase of the RWWSI. Whereas Rayleigh waves generated by
Lorentz force due to the static magnetic field decreases slowly when the RWWSI
increases.
The excitation current density decreases almost linearly with the increase
of the RWWSI. The Lorentz force distribution due to the dynamic magnetic
field has close relationship with the excitation current amplitude, and the force
amplitude is proportional to the inverse square of the RWWSI, whereas the
Lorentz force due to the static magnetic field is proportional to the reciprocal
of the RWWSI, as shown in Fig. 7. Z-direction force is the main component of
the Lorentz force due to the dynamic magnetic field, whereas Y-direction force
is the main component of the Lorentz force due to the static magnetic field.
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