Title

Modal testing using two speakers and application to the space shuttle tiles bond evaluation

Abstract

This paper concerns the application of two-speaker acoustic excitation in modal testing. Single-speaker excitation is first reviewed, and it is shown that anti-symmetric modes can not be adequately excited and measured when a uniform sound pressure is applied to the structure since the generalized forces are zeros. However, the two-speaker excitation method is shown to be effective in modal testing conducted on an aluminum plate and on the Space Shuttle tiles. The excitation signals are from the same function generator, but 180° out of phase. A laser vibrometer is used to measure the induced vibration. Data is acquired and processed using a two-channel spectrum analyzer, modal analysis software, and other instrumentation. The mode shapes (both symmetric and anti-symmetric) of the aluminum plate are determined experimentally and by finite element analysis. These results are shown to be in close agreement. This method of excitation, along with an inverse approach, is successfully implemented in the Space Shuttle tile bond evaluation. In this, the size and location of the disbonded regions are computed and displayed. The developed system for tile testing is shown to be quick, accurate, and user-friendly.

Publication Date

12-1-1997

Publication Title

Proceedings of the International Modal Analysis Conference - IMAC

Volume

1

Number of Pages

7-12

Document Type

Article; Proceedings Paper

Personal Identifier

scopus

Socpus ID

0031332154 (Scopus)

Source API URL

https://api.elsevier.com/content/abstract/scopus_id/0031332154

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