Wave Propagation in Functionally Graded 1-D Acoustic Black Hole via Viscoelastic Local Interaction Simulation Approach

Hui Zhang

The acoustic black hole (ABH) effect produces drastic wave compression and energy trapping in thin-walled structures. Recent research has shown that the reflected wave in realistic ABH structures can be reduced by attaching specific wave concentration areas with thin absorbing layer.

In this work, the novel design and implementation of one-dimensional (1D) functionally graded acoustic black hole (FGABH) are studied, as an alternative to achieve low reflection effect. Two kinds of the FG-ABHs are demonstrated, i.e., an axially graded ABH and a thickness graded ABH. The FG-ABH beams are manufactured by 3D printing technology using an Objet Connex 500 printer. Materials with varying levels of rubber-like characteristics are produced using two base materials called TangoPlus and VeroWhitePlus. The FG-ABH beams have both diminishing thickness and elastic modulus from the uniform area to the tip of the wedge.

Numerical investigation of wave propagation, attenuation and reflection are conducted utilizing a viscoelastic code: University of Michigan’s Local Interaction Simulation Approach (UM/LISA). The damping effect of the materials is included based on Kelvin-Voigt viscoelasticity theory. Finally, the process of wave propagation in FG-ABHs, traditional ABH and uniform beam are experimentally investigated using a scanning laser doppler vibrometer (SLDV) system. The reflection coefficients based on the ratios between the amplitude of reflected wave and incident wave are computed. Results indicate that the FG-ABHs enhance the ABH effects, and lower reflection is observed when compared to the traditional ABH structure.

The designs of the two FG-ABH compared to tranditional ABH without damping layer

here.

The reflection coefficient plots of the several different FG-ABH design are shown below

here.

For more information about the algorithm and features, please check the following references.

References

  1. Wei Huang, Hui Zhang, Hongli Ji, Carlos E. S. Cesnik, Jinhao Qiu, Daniel J. Inman, “Numerical Analysis of Wave Propagation in Functionally Graded 1-D Acoustic Black Hole via Viscoelastic Local Interaction Simulation Approach, INTER-NOISE (2018).

  2. Wei Huang, Hui Zhang, Daniel J. Inman, Jinhao Qiu, Carlos E. S. Cesnik, Hongli Ji, “Low Reflection Effects by 3D-Printed Functionally Graded Acoustic Black Holes”. (Under review, 2018).