A new continuous ultrasonic viscometer employing a pulsed resonant exponentially damped magnetostrictive strip is described and treated theoretically. Properties of viscoelastic materials affecting the propagation of transverse elastic waves are derived and are related to the response of the viscometer. Typical applications of the use of the ultrasonic viscometer are presented.

1.
In this paper, a non‐Newtonian material is one for which rate of shear is not directly proportional to shear stress as the magnitude and/or the frequency of the shear stress is varied. Effects of frequency are included in this definition, since some materials showing no measurable non‐Newtonianism owing to variations in magnitude of shear stress do exhibit change in viscosity as frequency of shear varies. Some silicone oils behave in this way.
2.
Ultra‐Viscoson, developed by the Rich‐Roth Laboratories, Hartford, Connecticut, manufactured by Cincinnati Division, Bendix Aviation Corporation, Cincinnati, Ohio.
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4.
Velocity of propagation of compressional elastic wave in a wire in which the diameter is very much less than one wavelength.
5.
The Ultra‐Viscoson will operate with transverse waves polarized in the plane of the strip or with torsional waves if a round rod is used instead of a strip. The analysis is similar in these other cases, so only the compressional mode, which is the case of most immediate importance, is discussed here.
6.
This assumption has proved to be true in all materials experimentally examined, including even mercury.
7.
W. P. Mason, Piezoelectric Crystals and Ultrasonics (D. Van Nostrand Company, Inc., New York, 1950), chap. 14;
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8.
Lord Rayleigh, Theory of Sound Vol. II, p. 317 (Dover Publications, New York, 1945).
9.
The negative sign is introduced since acoustic wave impedance is usually employed with pressure rather than stress and, in accordance with usual sign conventions, a positive pressure is equivalent to a negative stress.
10.
J. C. Slater, Microwave Transmission (McGraw‐Hill Book Company, Inc., New York, 1942), chap. 1.
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