Page 317 - Introduction to Naval Architecture

302 VIBRATION, NOISE AND SHOCK

In warships essential equipment is designed to remain operable up to
a level of shock at which the ship is likely to be lost by hull rupture. The
first of class of each new design of warship is subjected to a shock trial in
which its resistance to underwater shock is tested by exploding large
charges, up to 500 kg, fairly close to the hull

SUMMARY
The three closely related phenomena of vibration, noise and shock
have been reviewed. Each topic is important in ship design and levels of
vibration and noise must meet internationally agreed standards. Shock
is especially important for warships which must be able to withstand
enemy attack. Considerable advances have been made in recent years
in applying finite element analysis and statistical energy analysis to
these problems but the mathematics is beyond the scope of this book
and it has only been possible to outline the main features of each and
how the designer can deal with them. Having calculated, during design,
the vibration amplitudes expected, these can be checked as the build
nears completion, by setting up and running a vibration generator on
board. Finally the ship's acceptance trials are the final demonstration of
how successful a designer has been in reducing vibration and noise
levels to acceptable limits. In vibration some simplified formulae are
given upon which preliminary design assessments can be based.

References
1. Dieudonne, J. (1959) Vibration in ships. TINA.
2. Schlick, O. (1884) Vibration of steam vessels. TINA.
3. Todd, F. H. (1961) Ship hull vibration. Arnold,
4. Taylor, J. L. (1924-5) The theory of longitudinal bending of ships. TNECEES.
5. Taylor, J. L. (1927-8) Ship vibration periods. TNECJES.
6. Johnson, A. J. (1950-1) Vibration tests on all welded and riveted 10000 ton dry
cargo ships. TNEC1ES.
7. Burrill, L. C. (1934-5) Ship vibration: simple methods of estimating critical
frequencies. TNECIES.
8. Lewis, F. M. (1929) The inertia of water surrounding a vibrating ship. TSNAME.
9. Landweber, L. and deMacagno, M. C. (1957) Added mass of two dimensional forms
oscillating in a free surface, Journal of Ship Research, SNAME.
10. Taylor, J. L. (1930) Vibration of ships. TINA.
11. Towroin, R. L. (1969) Virtual mass reduction factors: J values for ship vibration
calculations derived from tests with beams including ellipsoids and ship models.
TMNA.
12. BS 6634: 1985. ISO 6954: 1984. Overall evaluation of vibration in merchant ships.
13. Warnaka, G. E. (1982) Active attenuation of noise - the state of the art. Noise Control
Engineering.