An instrument measuring ship's vibration

Related Terms

OVERTONE

One of the normal modes of vibration of a vibrating system whose frequency is greater than that of the fundamental mode.

NORMAL MODE OF VIBRATION

Vibration of a coupled system in which the value of one of the normal coordinates oscillates and the values of all the other coordinates remain stationary.

NORMAL FREQUENCIES

The frequencies of the normal modes of vibration of a system.

MISTUNING

The difference between the square of the natural frequency of vibration of a vibrating system, without the effect of damping, and the square of the frequency of an external, oscillating force.

MICRODIFFUSIOMETER

A type of diffusiometer in which diffusion is measured over microscopic distances, greatly reducing the time required for the measurement and the effects of vibration and temperature changes.

MECHANOOPTICAL VIBROMETER

A vibrometer in which the motion given to a probe by a surface whose vibration amplitude is to be measured is used to rock a mirror; a light beam reflected from the mirror and focused onto a scale provides an indication of the vibration amplitude.

KENNEDY AND PANCU CIRCLE

For a harmonic oscillator subject to hysteretic damping and subjected to a sinusoidally varying force, a plot of the in-phase and quadrature components of the displacement of the oscillator as the frequency of the applied vibration is varied.

ISOLATOR

1. A passive attenuator inw hich the loss in one direction is much greater than that in the opposite direction; a ferrite isolator for waveguides is an example. 2. Any device that absorbs vibration or noise, or prevents its transmission.

INHERENT DAMPING

A method of vibration damping which makes use of the mechanical hysteresis of such materials as rubber, felt, and cork.

HYSTERESIS DAMPING

Damping of a vibration due to energy lost through mechanical hysteresis.

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