Composite Materials Research Progress

Eletromechanical Field Concentrations and Polarization Switching... 265
normal stress at the interface, the dashed line represents the normal stress near the internal
electrode tip, and the alternate long and short dashed line denotes the value near the surface
electrode tip. The normal stress at the interface is singular at the electrode tip. The stress
ahead of the electrode tip is tensile, while the stress behind the electrode tip is compressive.
The values of the normal stress near the internal electrode tip are higher than those near the
Displacem ent,u z (�m )
2
1
0
-1
-2
FEA
W ork
x = 0 m m
y = 0 m m
z = 10 m m
L = 30 m m
W = 10 m m
4h = 20 m m
a = 20 m m
24
28
-1000 0 1000
Voltage,V 0 (V)
Figure 4. Normal stress versus x for laminated actuator under E0 =0.2 MV/m.
surface electrode tip. Fig. 5 shows the comparison of the distribution of the shear stress σzx
against x near the internal electrode tip with that near the surface electrode tip for the same
laminated actuator. The shear stress peaks at about x =5.5 mm, and the peak value near
the internal electrode tip is higher than that near the surface electrode tip.
Surface electrode
h
h
x
z
b
O
b �
b
c
r
Internal electrode
Figure 5. Shear stress versus x for laminated actuator under E0 =0.2 MV/m.
y