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Ultrasonic testing with phased arrays

Since 2009, KARL DEUTSCH is shareholder of the French company M2M, a well-known supplier for phased array testing electronics (also see www.m2m-ndt.com). M2M offers a large variety of test electronics. Multiplexed and parallel units with configurations between 16 up to 1024 channels are available. Hybrid testing systems using a mix of mono-element and phased array probes are possible and are pre-configured concerning the connectors (usually LEMO and Hypertronix, respectively). Furthermore, KARL DEUTSCH owns and operates the market-leading ultrasonic simulation software CIVA (developed by the CEA in France) which is an important tool to design the phased array probes for the respective test task and to theoretically estimate the achievable test results. Each M2M-unit comes with a basic version of the CIVA software to allow system users to verify the optimum test parameters and to improve the performance of the testing system.

Basic knowledge on phased arrays technique
The phased array technique provides electronic alteration of the sound beam of a probe. For this purpose the probe is divided into individual elements. Each element is electrically controlled by a separate test channel. Controlling of each element takes place at different points in time (time delays, so-called delay Laws) and possibly with different amplitudes. The superposition of elementary sound fields generates a resulting sound field. The active element group is often referred to as virtual probe. By means of angle panning a phased array probe is able to scan a large test area. It is also possible (within the near field of the virtual probe) to set different focus points and vary the test sensitivity in volume electronically.

A linear array permits controlling of a sound field in one plane. A matrix array allows for two-dimensional cluster panning, however, a large amount of channels is required. Round arrays (with or without segmentation, examples to be seen on the right-hand side of the image) are rarely used.

Due to different timing of individual elements (symbolized by different levels of red bars per element), different focal depths result. In case b) a focal point near to the surface is set.

Angle panning
In this example, the phased array is pre-mounted on a plastic wedge. By varying temporal control of the individual elements, different test angles arise. (α 1 and/or α 2).

Tube testing with linear scan
In this example, an internal groove is detected in an RF-welded pipe using a 45° test angle. The phased array has 96 elements; the virtual probe used has 16 elements. On the right another 18 virtual probes are indicated by means of lines. The pitch (line distance) is electronically adjustable. The activation of adjacent virtual probes within a phased array is called linear scan. This allows for a large testing volume with a phased array.

Further reading

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07 - 10 May 2019
33rd Control, Stuttgart

27 - 29 May 2019
DACH Annual Meeting, Friedrichshafen

14 - 17 October 2019
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