Phased array ultrasonics (PA) is an advanced method of

ultrasonic testing Ultrasonic testing (UT) is a family of non-destructive testing techniques based on the propagation of ultrasonic waves in the object or material tested. In most common UT applications, very short ultrasonic pulse-waves with center frequencies ...

that has applications in medical imaging and industrial nondestructive testing. Common applications are to noninvasively examine the heart or to find flaws in

manufactured Manufacturing is the creation or production of goods with the help of equipment, labor, machines, tools, and chemical or biological processing or formulation. It is the essence of secondary sector of the economy. The term may refer to a ran ...

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 Ultrasound is sound waves with frequencies higher than the upper audible limit of human hearing. Ultrasound is not different from "normal" (audible) sound in its physical properties, except that humans cannot hear it. This limit varies fr ...

testing is based on principles of

wave In physics, mathematics, and related fields, a wave is a propagating dynamic disturbance (change from equilibrium) of one or more quantities. Waves can be periodic, in which case those quantities oscillate repeatedly about an equilibrium (re ...

physics Physics is the natural science that studies matter, its fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge which r ...

, which also have applications in fields such as

optics Optics is the branch of physics that studies the behaviour and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behaviour of visible, ultraviole ...

and electromagnetic

antenna Antenna ( antennas or antennae) may refer to: Science and engineering * Antenna (radio), also known as an aerial, a transducer designed to transmit or receive electromagnetic (e.g., TV or radio) waves * Antennae Galaxies, the name of two collid ...

Principle of operation

The PA probe consists of many small

ultrasonic transducer Ultrasonic transducers and ultrasonic sensors are devices that generate or sense ultrasound energy. They can be divided into three broad categories: transmitters, receivers and transceivers. Transmitters convert electrical signals into ultrasoun ...

s, 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 Construction is a general term meaning the art and science to form objects, systems, or organizations,"Construction" def. 1.a. 1.b. and 1.c. ''Oxford English Dictionary'' Second Edition on CD-ROM (v. 4.0) Oxford University Press 2009 and com ...

, 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. Apart from detecting flaws in components, phased array can also be used for wall thickness measurements in conjunction with

corrosion Corrosion is a natural process that converts a refined metal into a more chemically stable oxide. It is the gradual deterioration of materials (usually a metal) by chemical or electrochemical reaction with their environment. Corrosion engi ...

testing. Phased array can be used for the following industrial purposes: *Inspection of welds *Thickness measurements *Corrosion inspection *PAUT Validation/Demonstration Blocks *Rolling stock inspection (wheels and axles) *PAUT & TOFD Standard Calibration Blocks

Features

*The method most commonly used for medical ultrasonography. *Multiple probe elements produce a steerable and focused beam. *Focal spot size depends on probe active aperture (A), wavelength (λ) and focal length (F). Focusing is limited to the near field of the phased array probe. **

\text = F\lambda/A

\text = A^2/4\lambda

*Produces an image that shows a slice through the object. *Compared to conventional, single-element

systems, PA instruments and probes are more complex and expensive. *In industry, PA technicians require more experience and training than conventional UT technicians.

Standards

;

European Committee for Standardization The European Committee for Standardization (CEN, french: Comité Européen de Normalisation) is a public standards organization whose mission is to foster the economy of the European Single Market and the wider European continent in global t ...

(CEN) *prEN 16018, ''Non destructive testing - Terminology - Terms used in ultrasonic testing with phased arrays'' *ISO/WD 13588, '' Non-destructive testing of welds – Ultrasonic testing – Use of (semi-) automated phased array technology''

References

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Books

*
ASME Boiler and Pressure Vessel Code
'. American Society Of Mechanical Engineers, 2013. Section V — ''Nondestructive Examination''. ee Article 4 — ''Ultrasonic Examination Methods for Welds''. Para E-474 ''UT-Phased Array Technique''

External links

''FOCUS - Fast Object-oriented C++ Ultrasound Simulator''
ATLAB routines for creating and simulating phased arraysbr>Phased array animated simulator
egistration required after 5 minutes' usebr>Phased Array Tutorial
Education resource from Olympus Nondestructive testing Ultrasound Medical ultrasonography