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Advantages of Phased-array Ultrasonic Inspection

Feb. 08, 2023

For non-destructive testing (NDT), the industry is increasingly using phased-array ultrasonic testing (PAUT). It is replacing other traditional ultrasonic and radiographic NDT methods with its high detection and accurate measurement capabilities. For industries such as aerospace, power generation, and pipeline services, phased-array ultrasonic inspection offers many advantages.


Phased-array ultrasonic inspection methods

Phased-array ultrasonic inspection methods operate with a series of small transducers in a single assembly that can emit pulses individually. The beam emitted from these individual transducers can therefore be controlled and can be focused and swept along the material without the need to move the probe. The pulse timing of each transducer is controlled by a computer. The results obtained from the reflected pulses are analyzed to identify defects in the material. The ability to optimize beam angle and focal length make the PAUT an effective method for determining material quality. The PAUT can be used for volumetric applications including weld inspection, corrosion inspection, and material thickness measurement.


How does a phased array work?

As described above, a phased-array ultrasonic flaw detection probe consists of a number of piezoelectric crystals that transmit/receive independently at different times. Using a time delay to focus the ultrasound beam, the time delay is applied to the elements to produce phase length interference in front of the wave. This interference allows the energy to be focused at any depth and angle in the specimen.

HS PA20-Ex Multi-function Phased Array Ultrasonic Flaw Detector

 HS PA20-Ex Multi-function Phased Array Ultrasonic Flaw Detector

Phased Array Ultrasonic Detection (PAUT)

Each element radiates a spherical wave at a specified time, producing converging and diverging waves, thus creating an almost planar wave front at a specified location. Varying the progressive time delay allows the beam to be electronically controlled and swept through the test material like a searchlight. When multiple beams are placed together, it creates a visual image showing a slice of the test object.


Different techniques can be used with the PAUT system.

Total Focus Method (TFM)

This method involves applying the basic phased-array focusing principle to a defined area of interest. The inspection area is divided into a grid of positions or pixels and beamforming is applied to each pixel in the grid.


Electronic scanning

Electronic scanning reproduces the inspection performed by manually moving a standard UT probe. The ultrasonic beam is electronically translated over the entire probe, thus speeding up the inspection while limiting mechanical displacement. The technique can be performed using either S- or L-wave and can be combined with beam focusing and beam control.


 HS PA30-E Ultrasonic Phased Array Detector

HS PA30-E Ultrasonic Phased Array Detector

Sector scanning

Sector scanning uses the electronic delay law to electronically change the angle of the ultrasonic beam in a defined sector. This means that only one transducer is required to detect components at different angles and is also much faster than standard oblique beam UT, displaying the cross section of the sample in real time and allowing easier interpretation. The technique can be combined with electronic focusing for both L- and S-waves.


Advantages of phased-array ultrasonic inspection

The PAUT offers many advantages over other NDT methods, including


Increased flaw detection capability

In PAUT, the probe is used to guide and control the direction and shape of the beam produced by the transducer. Unlike eddy current techniques, the beam can be controlled to scan the surface at different angles. Controlled scanning and optimised control allows increased coverage to detect defects in the material. Complex geometries of material can be inspected by controlling the beam at an angle, which may be difficult to do when operating manually.  

Multi-function Phased Array Ultrasonic Flaw Detector HS PA20-Aex

Multi-function Phased Array Ultrasonic Flaw Detector HS PA20-Alex


The PAUT is also effective in determining the thickness of the material. During the inspection, ultrasound can be used to determine any changes in material thickness due to corrosion or erosion.


Increased inspection speed

Phased array probes use multiple transducers, which helps to inspect larger surfaces in a short time. Multiple inspections can be carried out using a single probe, saving time spent reconfiguring and changing probes for each unique test.


Using a phased array system, digital feedback can be received instantly. This helps to identify defects and understand weld quality faster.


Reliability of results

Phased array probes can provide test results with an excellent repeatability factor. The ability to inspect complex geometries and detect defects makes the PAUT a reliable testing method.

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