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Modes of Vibration of High Speed Ship Hull Sections

conference contribution
posted on 2023-05-23, 05:46 authored by Michael DavisMichael Davis, Davidson, G, Roberts, T, Cato, CA
Impact testing of a typical high speed ship section has shown that the mode of vibration most likely to fall in the frequency range of excitation due to propeller or rotor blade passing is that where the ship frame rocks in a fore and aft direction about its base connection to the hull plate. This vibration has significant amplitude to either side of the keel and it is found that connection between the inboard and outboard sides is weak. As a consequence vibration can occur in two modes in which the opposite sides of the hull either move together or in anti phase. This leads to the structural strain energy in the two modes being slightly different, the mode with opposite motion to either side involving rather smaller strain energy. As a consequence the two modes have slightly different frequency, the mode with opposite motion to either side having rather less strain energy and thus a lower frequency. Because the frequencies of the two modes are thus close together the transient response exhibits beating in which vibration energy is exchanged between the two sides of the hull at the low beat frequency. Vibration of the ship frames in this manner appears to have been the cause of minor weld cracking where the top of stiffeners pass through cut outs in the web of the ship frames within the fuel tank areas of the hull.

History

Publication title

Proc 11th International Conference on Fast Sea Transportation

Editors

Todd J Peltzer, Chairman Organizing and National Scientific Committees

Pagination

524-531

Department/School

School of Engineering

Publisher

American Society of Naval Engineers

Place of publication

Honolulu, Hawaii

Event title

FAST: International Conference on Fast Sea Transportation

Event Venue

Waikiki, Honolulu

Date of Event (Start Date)

2011-09-26

Date of Event (End Date)

2011-09-29

Rights statement

Copyright 2011 American Society of Naval Engineers

Repository Status

  • Restricted

Socio-economic Objectives

Domestic passenger water transport (e.g. ferries)

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