ASA 127th Meeting M.I.T. 1994 June 6-10

3aED2. Identification of sound radiation from a discontinuity.

Patricia L. Driesch

Dept. of Aerosp. Eng. and Eng. Mech., Iowa State Univ., 2019 Black Engineering, Ames, IA 50011

The identification the of far-field sound radiation from a discontinuity on a beam is accomplished using a time-domain-based method that identifies the variations in wave propagation caused by the discontinuity. This identification of the far-field sound radiation includes determining the significance that each local variance in the metal has on the far-field sound radiation. The local variances are the material variances, geometric variances, and the applied stresses. To isolate the effects of the local variances on the far-field sound radiation, comparisons of many cases were made. The cases included aluminum versus steel, no discontinuity versus both a bolted and welded rib attachment, and a welded rib attachment versus the same geometry machined from one-piece of metal. Comparisons of these cases displayed a significant amount of far-field sound radiation around the rib attachment. These cases also displayed reflections of the structural waves at the rib attachment location. There were differences between the aluminum and steel cases, indicating a dependency upon the material. [Sponsored by ONR, Grant No. N00014-93-1-0493.]