Standard Practice for Contact Ultrasonic Testing of Welds Using Phased Arrays

Importancia y uso:

5.1 Phased array ultrasonic testing (PAUT) is an advanced examination technique used for enhanced flaw detection, sizing, and imaging as compared to conventional UT employing single-element transducers. PAUT utilizes multi-element (array) probes in which groups of elements are pulsed with pre-calculated time delays (“focal laws”) for each element (“phasing”). The resulting constructive and destructive interference allows for electronic steering, shaping, and focusing of the sound beam.

5.2 Though primarily a method of generating and receiving ultrasound, phased arrays are also a method of scanning and imaging. The two basic types of scans are the Linear or Electronic scan (E-Scan) and the Sectorial or Azimuthal scan (S-Scan). In the E-Scan, which emulates a manual scan, multiple sound beams are created at the same refracted angle. The beam is electronically translated along the active axis of the array by sequentially adding an element on one end and dropping an element off the other end of the active group of elements within the probe, with time multiplexing coordinated by the instrument’s on-board processor. In the S-Scan, which is unique to phased arrays, the sound beam is electronically swept through a range of user-defined angles by sequentially changing the time delays applied to each element. Because the beam angle is no longer solely dependent upon the wedge angle, more complete data can be obtained and more complex geometries can be examined versus conventional UT. With their distinct features and capabilities, phased arrays require special set-ups and standardization, as addressed by this practice. Commercial software permits the operator to easily make set ups without detailed knowledge of the phasing requirements.

5.3 Phased arrays can be used in different ways: manual or encoded linear scanning; and different displays or combinations of displays. In manual scanning, the dominant display will be an S-scan with associated A-scans. S-scans have the advantage over E-scans in that all the specified examination angles can be covered at the same time.

5.4 The main advantages of using phased arrays for ultrasonic weld examinations are:

5.4.1 Increased control of beam characteristics, including capability for focusing and steering the beam;

5.4.2 Faster scanning and increased probability of detection due to multiple lines/angles acquired and displayed in a single pass;

5.4.3 Increased ability to examine complex geometries and areas with limited access;

5.4.4 Better imaging from the true depth S-scan;

5.4.5 Digital data storage capability, which is intended to enable auditing, archiving, and off-line post-processing, re-processing, and comparison of data from different examinations;

5.4.6 Rapid and reproducible set-ups with electronic instruments.

Subcomité:

E07.06

Referida por:

E3170_E3170M-18R23, E0543-21, E3044_E3044M-22, E0543-21

Volúmen:

03.04

Número ICS:

25.160.40 (Welding joints and welds)

Palabras clave:

nondestructive testing; PAUT; phased arrays; phased array probe; ultrasonic contact examination; ultrasonic NDT of welds; welds;