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Technical Briefs

Dynamic Hydroelastic Scaling of the Underwater Shock Response of Composite Marine Structures

[+] Author and Article Information
Erin E. Bachynski

Centre for Ships and Ocean Structures,  Norwegian Univ. of Science and Tech., 7491 Trondheim, Norway e-mail: erin.bachynski@ntnu.no.

Michael R. Motley1

Postdoctoral FellowDept. of Naval Arch. and Marine Eng.,  University of Michigan, Ann Arbor, MI, 48109 e-mail: mmotley@umich

Yin L. Young2

Associate Professor Dept. of Naval Arch. and Marine Eng.,  University of Michigan, Ann Arbor, MI, 48109 e-mail: ylyoung@umich.edu

1

Permanent address: Princeton University, Princeton, NJ, 08544.

2

Corresponding author.

J. Appl. Mech 79(1), 014501 (Nov 14, 2011) (7 pages) doi:10.1115/1.4004535 History: Received December 31, 2009; Revised July 06, 2011; Posted July 07, 2011; Published November 14, 2011; Online November 14, 2011

The hydroelastic scaling relations for the shock response of water-backed, anisotropic composite marine structures are derived and verified. The scaling analysis considers the known underwater explosion physics, previously derived analytical solutions for the underwater shock response of a water-backed plate, and elastic beam behavior. To verify the scaling relations, the hydroelastic underwater shock response of an anisotropic composite plate at several different scales is modeled as a fully coupled fluid-structure interaction (FSI) problem using the commercial Lagrangian finite element software ABAQUS/Explicit. Following geometric and Mach similitude, as well as proper scaling of the FSI parameter, scaling relations for the structural natural frequencies, fluid and structural responses are demonstrated for a variety of structural boundary conditions (cantilevered, fixed-fixed, and pinned-pinned). The scaling analysis shows that the initial response scales properly for elastic marine structures, but the secondary bubble pulse reload caused by an underwater explosion does not follow the same scaling and may result in resonant response at full scale.

FIGURES IN THIS ARTICLE
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Copyright © 2012 by American Society of Mechanical Engineers
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References

Figures

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Figure 1

Top view and elevation view of model domain. Shaded regions are in the solid domain; white regions are in the fluid domain. Note that Xf  = Xs for the fixed-fixed and pinned-pinned boundary conditions.

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Figure 2

Comparison of wetted natural period to shock pressure decay time for the cantilevered (Cant.), fixed-fixed (FF), and pinned-pinned (PP) CFRP and NAB plates at prototype, half, and eighth scale. θ  = 0.26 ms (prototype), W = 10 kg (prototype), R = 10 m (prototype).

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Figure 3

CFRP (left) and NAB (right) cantilevered plate interface pressure at the tip, midpoint (MID), quarter point (QTR), and root along the centerline (midchord). L = 1.68 m (prototype), Po  = 8.52 MPa, θ  = 0.26 ms (prototype).

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Figure 4

CFRP cantilevered (left), fixed-fixed (middle) and pinned-pinned (right) plate front side interface pressure along the centerline (midchord) at prototype, half, and eighth scale. L = 1.68 m (prototype), Po  = 8.52 MPa, θ  = 0.26 ms (prototype).

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Figure 5

CFRP (left) and NAB (right) cantilevered plate deflection at the tip, midpoint (MID), quarter point (QTR), and root along the centerline (midchord). L = 1.68 m (prototype), Po  = 8.52 MPa, θ  = 0.26 ms (prototype).

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Figure 6

CFRP (left) and NAB (right) cantilevered plate stresses at the root, front face, centerline. L = 1.68 m (prototype), Po  = 8.52 MPa, θ  = 0.26 ms (prototype).

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Figure 7

Comparison of wetted natural frequencies to shock pressure decay constant for the cantilevered (Cant.), fixed-fixed (FF), and pinned-pinned (PP) CFRP and NAB plates at prototype, half, and eighth scale. θ  = 0.26 ms (prototype), W = 10 kg (prototype), R = 10 m (prototype)

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