Open Access

ARTICLE

Modeling and Measurement of a Tunable Acoustoelastic System

Deborah Fowler¹, Garrett Lopp², Dhiraj Bansal³, Ryan Schultz⁴, Matthew Brake⁵, Micah Shepherd⁶

1 Undergraduate Student, University of Massachusetts, Lowell, 01854
2 Graduate Research Assistant, University of Central Florida, Orlando, FL, 32816
3 Graduate Student, University of Colorado Boulder, Boulder, CO 80309
4 Sandia National Laboratories, PO Box 5800-MS0557, Albuquerque, NM, 87123
5 Assistant Professor, William Marsh Rice University, 6100 Main St, MS 321, Houston, TX 77005
6 Assistant Research Professor, The Pennsylvania State University, PO Box 30, State College, PA 16804
The author can be reached at: rschult@sandia.gov.

Sound & Vibration 2018, 52(3), 12-17. https://doi.org/10.32604/sv.2018.03864

Abstract

Acoustoelastic coupling occurs when a hollow structure’s in-vacuo mode aligns with an acoustic mode of the internal cavity. The impact of this coupling on the total dynamic response of the structure can be quite severe depending on the similarity of the modal frequencies and shapes. Typically, acoustoelastic coupling is not a design feature, but rather an unintended result that must be remedied as modal tests of structures are often used to correlate or validate finite element models of the uncoupled structure. Here, however, a test structure is intentionally designed such that multiple structural and acoustic modes are well-aligned, resulting in a coupled system that allows for an experimental investigation. First, coupling in the system is identified using a measure termed the magnification factor. Next, the structural-acoustic interaction is measured. Modifications to the system demonstrate the dependency of the coupling on changes in the mode shape and frequency proximity. This includes an investigation of several practical techniques used to decouple the system by altering the internal acoustic cavity, as well as the structure itself. These results show that acoustic absorption material effectively decoupled the structure while structural modifications, in their current form, proved unsuccessful. Readily available acoustic absorptive material was effective in reducing the coupled effects while presumably adding negligible mass or stiffness to the structure.

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