Ultrasonic Testing (UT)

Definition - What does Ultrasonic Testing (UT) mean?

Ultrasonic testing (UT) is a nondestructive method of characterizing the thickness or internal structure of a test piece through the use of high-frequency sound waves. Ultrasonic testing can be used for:

  • Flaw detection/evaluation
  • Dimensional measurements
  • Material characterization

Ultrasonic testing is performed on steel as well as other metals and alloys. It can also be used on concrete, wood and composites, albeit with less resolution.

Ultrasonic testing is also known as ultrasonic nondestructive testing (ultrasonic NDT).

Corrosionpedia explains Ultrasonic Testing (UT)

Ultrasonic testing uses high-frequency sound waves (typically in the range between 0.5 and 15 MHz) to conduct examinations and take measurements. For example, an ultrasonic thickness measurement can test the thickness of an object to monitor pipework corrosion.

Ultrasonic testing is completely nondestructive. The test piece does not have to be cut, sectioned or exposed to damaging chemicals. Access to only one side is required, unlike measurement with mechanical thickness tools like calipers and micrometers. There are no potential health hazards associated with ultrasonic testing, unlike radiography. When a test has been properly set up, results are highly repeatable and reliable.

In ultrasonic testing, an ultrasound transducer connected to a diagnostic machine is passed over the object being inspected. In general, ultrasonic testing is based on the capture and quantification of either the reflected waves (pulse-echo) or the transmitted waves (through-transmission). Each of the two types is used in certain applications, but generally, pulse-echo systems are more useful since they require one-sided access to the object being inspected.

A typical pulse-echo UT inspection system consists of several functional units, including:

  • Pulser/receiver
  • Transducer
  • Display device

Ultrasonic flaw detection requires a trained operator who can set up a test with the aid of appropriate reference standards and properly interpret the results. Inspection of some complex geometry may be challenging. Ultrasonic thickness gauges must be calibrated with respect to the material being measured, and applications requiring a wide range of thickness measurement or measurement of acoustically diverse materials may require multiple setups. Ultrasonic thickness gauges are more expensive than mechanical measurement devices.

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