WAVES AND VIBRATIONS IN INHOMOGENEOUS STRUCTURES ...

c
Reflectance, R
7.1. Two-phase design
1.0
0.8
0.6
0.4
0.2
0.0
a
b
ARTICLE IN PRESS
0 200 400 600 800 1000 1200 1400 1600
Frequency [Hz]
Fig. 8. (a) Optimized distribution of scatter 1 (gray), scatter 2 (black) and host (white); (b) 2-phase design with host replaced by scattering
material; (c) resulting reflectance curves for P and S waves. P wave (solid line), S wave (dashed line), P wave-2 phase (discrete circles), S
wave-2 phase (discrete crosses).
Table 2
Material properties for the materials used in the dissipation example
Material r ðkg=m 3 Þ E (MPa) n Z r ðs 1 Þ
Host (ground) 1550 269 0.257 —
Epoxy 2000 4000 0.400 0.05
Scatter 3100 5380 0.350 —
The material data for the ground is taken from Ref. [23].
J.S. Jensen / Journal of Sound and Vibration 301 (2007) 319–340 333
In this section host and the absorptive material are used for the optimization. Fig. 10a shows an optimized
design for shear and pressure waves in a 10% frequency range near the center frequency with 10
optimization frequencies used. The optimized design is complicated but with characteristic features. A thin