NDT Systems TG400 Operator's Manual page 32

Thickness Gaging Procedures for Non-Metallic and Composite Materials.
To some extent, all of the previously described procedures can be applied to thickness gaging of
engineering materials other than metals. Because there are so many such materials, there will be no
attempt in this manual to detail them. Materials other than metals have their own unique properties
with respect to the transmission and propagation of ultrasonic energy. In general, the velocity of
ultrasound is lower and attenuation greater. Characteristics such as the presence of scattering
reflectors, impedance, an isotropy, Modula, and other physical and mechanical properties all interact
with ultrasonic sound beams somewhat differently than in metals.
Despite the differences, most polymers and glasses, some ceramics and composite materials can be
tested with the same transducers and procedures as for metals, except for the obvious adjustments
that may be required in calibration. Once the procedures for thickness gaging metals are understood,
experimentation with other materials is generally straightforward. Feel free to consult with NDT
Systems, Inc.' factory engineering personnel or technical field sales representatives on special
techniques/procedures.
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