ASA 129th Meeting - Washington, DC - 1995 May 30 .. Jun 06

5pSA6. Energy partitioning in a truss structure.

Kai-Ulrich Machens

Ira Dyer

Dept. of Ocean Eng., MIT, Cambridge, MA 02139

MIT is investigating both theoretically and experimentally wave propagation in truss structures. Experiments were conducted to measure energy partitioning in flexural, longitudinal, and torsional vibrations of specific truss members. The truss consists of 109 aluminum struts assembled via 35 joints to form a regular structure of 11 cells connected in series. A complete numerical analysis [Y. P. Guo, 3291(A) (1994)] finds that energy equilibria among different wave types can be expected, the ratios of which are dependent upon the distinct classes of struts making up the truss. This was tested by simultaneous measurement of the transfer functions at various locations along the axis of each strut considered. The truss was excited by broadband white noise (5-kHz baseband) at one end of the truss. Wave number processing extracts two complex wave amplitudes, each associated with traveling waves propagating in opposite directions. Thus the spectral energy content of the strut is known and is compared to others in the same class. In addition, struts of other classes are measured to discuss issues related to equipartition of energy, pass/stop bands and natural damping of complex branched structures.