Phased Array Technology
General Description of the Phased Array Technology
Phased array (PA) ultrasonic is an advanced method of ultrasonic testing that has a vast application in the industrial non-destructive testing. 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 active 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 wave physics, which also have applications in fields such as optics and electromagnetic antennae.
The PA probe consists of many small ultrasonic transducers, each of which can pulse and receive independently. By varying the time delays, for instance by pulsing the elements one by one in sequence along a row, a pattern of constructive interference is set up that results in a beam at a set angle. In other words, the beam can be focused and steered electronically. The beam is swept like a search-light through the object being examined.
Phased array technology is widely used for non-destructive testing (NDT) in many industrial sectors, such as materials examination, 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 and/or material 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.
Main Advantages of PA-Technology:
- One PAP can substitute many conventional probes;
- Fewer amount of mechanics;
- Fewer amount of required maintenance;
- PA-technology reduces participation of people in both calibration and test process.
That reduces a “Human factor” negative influence;
- The PAP increases reliability of the test process; it implies decrease in over-rejection.
How the PAP Works:
Conventional ultrasonic testing technique is typically based on application of piezoelectric probes with a very limited number of crystals intended for generating/receiving of ultrasonic waves. Such probes can only generate ultrasonic waves in one direction, determined by an initial design of the probe (see below).
The PA probe consists of many small elements, each of which can be pulsed separately. In the figure below the element on the right is pulsed first, and emits a pressure wave that spreads out like a ripple on a pond (largest semicircle). The second to right element is pulsed next, and emits a ripple that is slightly smaller than the first because it was started later. The process continues down the line until all the elements have been pulsed. The multiple waves add up to one single wave front travelling at a set angle. In other words, the beam angle can be set just by programming the pulse sequences and delays.
It is well known that the most significant feature of phased array probe is its flexibility - convenient and effective control of the beam shape and ultrasound field distribution parameters. The field parameters can be changed dynamically, thousands times a second by changing of delay of crystals excitation.
Because of the powerful software and sophisticated electronics, the system controls the piezoelectric elements of each PAP on an individual way.
Ultrasonic Testing Systems of NORDINKRAFT NDT GROUP, its Phased-Array transducers are well known for their precision and robustness.
Engineers of NORDINKRAFT NDT GROUP have developed more than 40 types of piezoelectric PA-probes intended for different applications. Innovative ultrasonic testing systems NORDINKRAFT are currently in a successful industrial operation all over the world. Our PAP-based products and services meet the highest technical and qualitative standards.
Products and services of NORDINKRFAT GROUP meet the highest standards.