Simple lightweight and flexible structures act as building blocks for larger more intricate systems. When subject to dynamic loads, these structures transmit vibrations that can compromise the integrity, stability and control of its connecting members. Specifically, we are focused on broadband low frequency applications where weight reduction becomes critical, such as with aerospace and underwater applications.
Our group has developed a novel solution known as Multi-Element Multi-Path (MEMP) design: a technique that utilizes the inherent dynamics of flexible structures rather than heavy damping and active controllers to reduce vibration transmission across the structure. Through this method, a simple structure is divided up into several constituent substructures with separate, elastically coupled, wave transmission paths to achieve substantial wide-band reductions in the low frequency range while satisfying constraints on static strength and weight. Attenuation is achieved through several processes acting in concert: different subsystem wave speeds, mixed boundary conditions at end points, interaction through elastic couplings, and stop band behavior.
The MEMP design has been incorporated into both multi-layered thin beams and concentric cylindrical shells with promising results. Experiments using two-layer aluminum beams excited by a shaker table reveal wideband reductions, verifying results and trends from our in-house algorithms. Applications include rotor design, sensor mounts and submarine hulls.
Selected References
Raudales, D. "Vibration Transmission Reduction Through Multi-Element Multi-Path Structural Design in Thin Beams and Cylindrical Shells" (Masters Thesis, Duke University, 2015).
Bliss, DB, Raudales, D, and Franzoni, LP. "A Study of Multi-Element/Multi-Path Concentric Shell Structures to Reduce Noise and Vibration" The Journal of the Acoustical Society of America 135, 2386. (2014).
Su, K. "Rotor Vibration Reduction Using Multi-Element Multi-Path Design" (Masters Thesis, Duke University, 2013).