Phased array ultrasonics (PA) is an advanced method of
ultrasonic testing that has applications in
medical imaging and industrial
nondestructive testing. Common applications are to
noninvasivelyexamine the heart or to find flaws in
manufactured materials such as
welds. Single-element (non-
phased array)
probes, known technically as monolithic probes, emit a beam in a fixed direction. To test or interrogate a large volume of material, a conventional probe must be physically scanned (moved or turned) to sweep the beam through the area of interest. In contrast, the beam from a phased array probe can be focused and swept electronically without moving the probe. The beam is controllable because a phased array probe is made up of multiple small elements, each of which can be pulsed individually at a computer-calculated timing. The term phased refers to the timing, and the term array refers to the multiple elements. Phased array
ultrasonic testing is based on principles of
wavephysics, which also have applications in fields such as
optics and electromagnetic
antennae.
Principle of operation
The PA probe consists of many small
ultrasonic transducers, each of which can be pulsed independently. By varying the timing, for instance by making the pulse from each transducer progressively delayed going up the line, a pattern of constructive interference is set up that results in radiating a quasi-plane ultrasonic beam at a set angle depending on the progressive time delay. In other words, by changing the progressive time delay the beam can be steered electronically. It can be swept like a search-light through the tissue or object being examined, and the data from multiple beams are put together to make a visual image showing a slice through the object.
Use in industry
Phased array is widely used for
nondestructive testing (NDT) in several industrial sectors, such as
construction, pipelines, and
power generation. This method is an advanced NDT method that is used to detect discontinuities i.e. cracks or flaws and thereby determine component quality. Due to the possibility to control parameters such as beam angle and focal distance, this method is very efficient regarding the defect detection and speed of testing.[1] Apart from detecting flaws in components, phased array can also be used for wall thickness measurements in conjunction with
corrosion testing.[2][3]
Phased array can be used for the following industrial purposes:
Multiple probe elements produce a steerable and focused beam.[6]
Focal spot size depends on probe active aperture (A), wavelength (λ) and focal length (F).[7] Focusing is limited to the near field of the phased array probe.
Produces an image that shows a slice through the object.
Compared to conventional, single-element
ultrasonic testing systems, PA instruments and probes are more complex and expensive.
In industry, PA technicians require more experience and training than conventional UT technicians.
^ASTM, E2700 (2012). Nondestructive Testing, vol 3.03, Contact Ultrasonic Testing of Welds using Phased Arrays. Conshohocken, PA: American Society for Testing of Materials. pp. 1536–44.
ISBN978-0-8031-8729-0.{{
cite book}}: CS1 maint: numeric names: authors list (
link)
^ASTM, E2491 (2012). Nondestructive Testing vol 3.03, Evaluating Phased Array Characteristics of Phased Array Ultrasonic Testing Instruments and Systems. Conshohocken, PA: American Society for Testing of Materials. pp. 1358–75.
ISBN978-0-8031-8729-0.{{
cite book}}: CS1 maint: numeric names: authors list (
link)
^Birring, Anmol (September 2008). "Selection of Phased Array Parameters for Weld Testing". Materials Evaluation.
Books
ASME Boiler and Pressure Vessel Code. American Society Of Mechanical Engineers, 2013. Section V — Nondestructive Examination. [See Article 4 — Ultrasonic Examination Methods for Welds. Para E-474 UT-Phased Array Technique