Accession Number : ADA290008

Title :   Experimental Validation of Finite Element and Boundary Element Methods for Predicting Structural Vibration and Radiated Noise.

Corporate Author : KENTUCKY UNIV LEXINGTON

Personal Author(s) : Seybert, A. F. ; Wu, T. W. ; Wu, X. F.

PDF Url : ADA290008

Report Date : JAN 1994

Pagination or Media Count : 95

Abstract : This research report is presented in three parts. In the first part, acoustical analyses were performed on modes of vibration of the housing of a transmission of a gear test rig developed by NASA. The modes of vibration of the transmission housing were measured using experimental modal analysis. The boundary element method (BEM) was used to calculate the sound pressure and sound intensity on the surface of the housing, and the radiation efficiency of each mode. The radiation efficiency of each of the transmission housing modes was then compared to theoretical results for a finite baffled plate. In the second part, analytical and experimental validation of methods to predict structural vibration and radiated noise are presented. A rectangular box excited by a mechanical shaker was used as a vibrating structure. Combined finite element method (FEM) and boundary element method (BEM) models of the apparatus were used to predict the noise level radiated from the box. The FEM was used to predict the vibration, while the BEM was used to predict the sound intensity and total radiated sound power using surface vibration as the input data. Vibration predicted by the FEM model was validated by experimental modal analysis, noise predicted by the BEM was validated by measurements of sound intensity. Three types of results are presented for the total radiated sound power: (1) sound power predicted by the BEM model using vibration data measured on the surface of the box: (2) sound power predicted by the FEM/BEM model; and (3) sound power measured by an acoustic intensity scan. In the third part, the structure used in part two was modified. A rib was attached to the top plate of the structure. The FEM and BEM were then used to predict structural vibration and radiated noise respectively. (MM)

Descriptors :   *VIBRATION, *HELICOPTERS, *NOISE REDUCTION, *TRANSMISSION GEARS, *RADIATED NOISE, *AIRCRAFT NOISE, FINITE ELEMENT ANALYSIS, DAMPING, BOUNDARY VALUE PROBLEMS, ACOUSTIC ATTENUATION, SOUND PRESSURE, HOUSINGS, MACHINERY NOISE, ACOUSTIC PROPERTIES, RIBS.

Subject Categories : Helicopters
      Acoustics
      Noise Pollution and Control

Distribution Statement : APPROVED FOR PUBLIC RELEASE