## 3pSA1. Is power equipartitioned in complicated structures?

### Session: Wednesday Afternoon, December 4

### Time: 2:00

**Author: Ira Dyer**

**Location: Dept. of Ocean Eng., MIT, Cambridge, MA 02139**

**Abstract:**

A tenet of statistical energy analysis is that power of an elastic wave is
partitioned equally among the substructures of an overall structure, and
prevails when modes of each overlap those of the other substructures. Is power
equipartition achieved for all complicated structures, specifically, for those
in which several wave types spatially coexist? Recent research equivocates: only
sometimes! Analysis by He for a finite-length ringed shell in water shows power
equipartition among compressional, shear, and flexural waves. But measurements
by Machens and Dyer, and by Bondaryk, on various 3-D truss structures in air, do
not show power equipartition. An explanation for the apparent contradiction in
these different structural systems is not, at this writing, worked out.
Speculations, however, point to the differences between scattering from one wave
type to another, on the shell and in the truss. On the shell, scattering at a
ring is distributed with finite width in helical angle. In the truss, scattering
is localized at truss joints. Both systems have spatial regularity and hence
stopbands, but the helical angle width on the shell can induce good wave--wave
spatial overlap, while no ``extra'' dimension is available in the truss to
counter the stopband rejections. [Supported by ONR.]

ASA 132nd meeting - Hawaii, December 1996