ASA 130th Meeting - St. Louis, MO - 1995 Nov 27 .. Dec 01

4aSA4. Time domain simulation and visualization of fuzzy structures.

Victor W. Sparrow

Graduate Prog. Acoust., Penn State Univ., 157 Hammond Bldg., University Park, PA 16802

Fuzzy structure formulations divide a complicated structure into a well-known master structure and an imprecisely known fuzzy substructure. The loss of energy from the master structure, now known in the fuzzy structures literature as apparent damping, is simply a transfer of energy into the internal degrees of freedom of the attached fuzzy substructure. Some energy in the substructure is not returned to the master structure if either the internal damping of the substructure is non-negligible or there are a large number of degrees of freedom in the substructure with closely spaced resonances. This paper will demonstrate such effects using transverse wave pulses propagating on simple master structures, strings, and rods. Sets of one degree of freedom (dof) oscillators, drawn from particular statistical distributions, are attached as the fuzzy substructure. Finite-difference models for the strings and rods are solved simultaneously with the dynamics of the attached one dof oscillators in the time domain. Videotape animations show both the displacements of the master structure and the attached oscillators. Quantitative comparisons are made to the recent results of Russell [J. Acoust. Soc. Am. 97, 3414--3415(A) (1995)]. [Work supported by ONR.]