1. The principles of Phased Array Ultrasonic Testing (PAUT):

PAUT is similar in principle to the conventional ultrasonic inspection, but it employs an array of ultrasonic transducers instead of a single probe. The advanced imaging technology allows the information gathered from the array of transducers to be displayed in ways that can be more intuitively interpreted for accurate results.

Picture 1: Equipment of PAUT.

Phased Array technology:

- The probe is composed of a small and discreet transducers.

- Each transducer element can be separately driven by varying the relative time delay:

• Called “ delay law” or “focal law”.
• Enabling to electrically steer or focus the sound beam.
• Without mechanical motion of the phased array probe.

- The response of each transducer element is independently received and processed. 

- Beam shaping is performed by pulsing the elements with different time delays.

Picture 2: The principles of Phased Array Ultrasonic Testing (PAUT).

2. Advantages and Disadvantages of PAUT:

- Advantages:

• Multiple transducer elements.
• Increased examination coverage.
• Flexibility to inspect geometries not possible with conventional UT techniques.
• Can be optimized for particular inspections.
• Sophisticated equipment and software.
• Real-time imaging.
• More intuitive display and better presentation of data.

- Disadvantages:

• Complex equipment more difficult to operate than conventional UT.
• Additional operator training required.
• First-time PA system set-up is very time-consuming.
• PA probes and wedges are larger than conventional UT probes.
• The higher cost of the whole system.
• The absence of widely accepted PA inspection standards and calibration blocks.