Modeling and Measurement of a Tunable Acoustoelastic System

Journal Article · Tue May 01 00:00:00 EDT 2018 · Sound and Vibration

DOI:https://doi.org/10.32604/sv.2018.03864· OSTI ID:1477453

Fowler, Deborah ^[1]; Lopp, Garrett ^[2]; Bansal, Dhiraj ^[3]; Schultz, Ryan ^[4]; Brake, Matthew ^[5]; Shepherd, Micah ^[6]

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1. Univ. of Massachusetts, Lowell, MA (United States)
2. Univ. of Central Florida, Orlando, FL (United States)
3. Univ. of Colorado, Boulder, CO (United States)
4. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
5. Rice Univ., Houston, TX (United States)
6. Pennsylvania State Univ., University Park, PA (United States)

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.

• Research Organization: Sandia National Laboratories (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1477453
• Report Number(s): SAND--2018-4962J; 663505
• Journal Information: Sound and Vibration, Journal Name: Sound and Vibration Journal Issue: 3 Vol. 52; ISSN 0038-1810
• Publisher: Tech Science Press
• Country of Publication: United States
• Language: English

Related Subjects

42 ENGINEERING
acoustic absorption
acoustic modes
coupled modes
modal testing
structural-acoustic interaction