Ultrasonic Testing (UT)

Ultrasonic testing is a non-destructive testing method that sends high-frequency sound waves into a material and analyses their reflection or transmission to detect internal defects, measure thickness and characterise material properties.

A transducer, usually piezoelectric, emits short pulses of ultrasound, typically in the megahertz range for industrial inspection, which travel through the material and reflect from boundaries such as the back wall or internal discontinuities. In the common pulse-echo technique, the time of flight of each echo indicates the depth of the reflector and its amplitude gives an indication of size. A couplant, such as gel or water, transmits sound between the probe and the part. Phased array probes steer and focus the beam electronically, and time-of-flight diffraction uses signals diffracted from crack tips for accurate sizing.

UT is used to inspect welds, forgings, castings, plates, pipes, composites and bonded structures, and to measure remaining wall thickness in pipes, tanks and pressure vessels affected by corrosion. Industries include aerospace, power generation, oil and gas, rail, where it is used on axles and rails, and automotive manufacturing. It can find volumetric and planar defects deep inside thick sections and gives immediate results.

UT requires skilled operators, suitable calibration blocks and written procedures, and results depend on surface condition, geometry, grain structure and defect orientation relative to the beam. Coarse-grained materials, such as some cast and austenitic steels, scatter sound and are harder to inspect. Personnel are commonly certified under ISO 9712 or equivalent schemes, and product and sector standards define techniques and acceptance criteria.

Key points

Uses high-frequency sound waves to find internal defects and measure thickness.
Pulse-echo time of flight gives the depth of a reflector.
Phased array and TOFD are advanced techniques for imaging and sizing.
Results depend on operator skill, calibration, geometry and material structure.

Where AiVibe comes in

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Ultrasonic Testing (UT)

Key points

Where AiVibe comes in

Related terms

Terms that refer to Ultrasonic Testing (UT)