Inspectioneering Journal

Dry-Coupled Ultrasonic Testing: An Effective, Yet Underutilized NDE Method

By Borja Lopez, President and CEO at Innerspec Technologies, Inc. This article appears in the November/December 2015 issue of Inspectioneering Journal.


The conversion of electrical pulses to mechanical vibrations and the conversion of returned mechanical vibrations back into electrical energy is the basis for ultrasonic testing (UT). Although there are non-contact options available for some applications (e.g. EMAT), the most widely used technique involves using a piezoelectric element to generate the ultrasound. Due to the impedance mismatch between the piezoelectric transducer and the material inspected, a liquid couplant is typically used to transmit the vibrations from the transducer into the part and receive the vibrations back into the transducer. While this technique is very efficient and popular, liquid couplants used for ultrasonic inspection have some inherent limitations and disadvantages. The liquid couplant itself is sensitive to extreme weather conditions, can be harmful to the part and environment, can make some inspections cumbersome or impossible, and their use and disposal can be expensive. An alternative method to using liquid couplant is Dry-Coupled Ultrasonic Testing (DCUT).

Applications and Advantages

A new family of piezoelectric transducers has recently been developed to withstand very high voltages and can be efficiently coupled through rubber with no need for liquid couplant. These DCUT transducers can be used to inspect metals, composites, and any material suited for ultrasound propagation with the following advantages over more conventional options

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Posted by mahendra kumar rastogi on February 16, 2016
Excellent information can short out many... Log in or register to read the rest of this comment.

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