Ultrasonic phased arrays use a multiple element probe whereby the output pulse from each element is time delayed in such a way so as produce constructive interference at a specific angle and a specific depth.
These time delays can be incremented over a range of angles to sweep the beam over the desired angular range. For example, 40 to 75 degree beam sweep would be produced by calculating the time delays to produce constructive interference at 40, 41, 42 …75 degs. This NDT technology is also referred as Swept Beam Ultrasonic testing. The main advantages of phased array in NDE are:
- Ability to sweep a range of angles
- Ability to display the image in real time for the swept angles
- Ability to focus
The above figure displays the concept of phased arrays. Time delays to the eight elements control focusing and beam sweep. Focal spot size (shown by the shaded orange area) is controlled by beam spread.
Checking Phased Array Probe Resolution. Resolution determines flaw definition and sizing accuracy. Instrument: Phasor