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Did You Know? Crystals Are Essential to NDT Transducers

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Just like a certain galactic super weapon, crystals are an essential component of transducers. The difference is that our transducers use crystals for nondestructive testing instead of blowing up planets.

Transducers use piezoelectric ceramic crystals to convert electrical energy into mechanical energy in the form of ultrasound and then convert returning ultrasound to electrical energy. These electrical signals are interpreted by a flaw detector to provide inspectors information about the test material. 

A diagram showing the inner workings of a transducer.
 

Transducer ceramic elements are cut in a crystalline lattice structure, which deforms in a predictable manner when pulsed with an electric current. The repeated deformation of the crystal face creates an ultrasonic wave that travels through the test material. The crystal structure can be oriented to maximize either longitudinal or shear deformation, creating longitudinal or shear ultrasonic waves. The thickness of the piezoelectric element determines the frequency of ultrasound generated: thicker crystal elements generate lower frequency ultrasound, while thinner crystal elements generate higher frequency ultrasound. 

The frequency used for a given thickness gaging application depends on a number of factors, including the acoustic properties of the inspection material and the required thickness resolution. The frequency used for a flaw detection application depends on the minimum allowable flaw size. 

Different types of transducers are made to suit a wide variety of inspection applications.


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Phil Graham has undergraduate degrees in history and anthropology, a master’s degree in the humanities from the University of Chicago, and a PhD in anthropology from the University of Connecticut. He spent many years teaching writing-intensive college courses before joining Evident. Phil enjoys using his training in the social sciences to communicate with the public about advanced technologies and products. 

December 16, 2016
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