M2M Gekko PAUT Phased Array Instrument with TFM, UT, TOFD (2023) (2023)

FAQs

What is the difference between UT and TOFD? ›

In practice, testing with the TOFD method is only applied by continuously moving the probe pair along the weld seam, while in traditional UT techniques the probe must be also moved perpendicular to the weld seam. Depending on the equipment the scan is performed either manually or by use of an automated manipulator.

While PAUT uses reflection, TOFD uses diffraction. The transducer produces pulsed ultrasonic waves, which are diffracted to various degrees by irregularities in the scanned material, then collected on the material's far side by a receiver.

Phased Array is an ultrasonic testing technique that uses specialized multi-element “array” transducers and pulses those elements separately in a patterned sequence called “phasing”. This phasing sequence allows wave steering, focusing, and scanning. This is all performed electronically.

A PAUT transducer uses multiple elements during a scan. Beams are emitted sequentially at multiple angles allowing PAUT to create a more detailed scan. Other UT methods, on the other hand, use a single probe to analyze an asset. By emitting multiple beams, PAUT allows for the inspection of even the most complex assets.

A disadvantage of TOFD is that the gain must be very high, which produces a very high back wall echo and it is not suitable for coarse grained materials. There is a dead zone for defect detection under the surface. It means, defects close to the surface could not be detected.

The main disadvantages of phased-array systems are that (i) they are more expensive to purchase, (ii) operation and data interpretation are more difficult and (iii) there can be greater difficulty in achieving good ultrasonic coupling due to the larger probe dimensions.

Each element radiates a spherical wave at a specified time, creating waves that converge and diverge to create an almost planar wavefront at the specified location. Changing the progressive time delay allows the beam to be steered electronically and swept through the test material like a searchlight.

Phased array antennas include multiple emitters and are used for beamforming in high-frequency RF applications. Three common application areas are in WiFi, chirped radar, and 5G.

Phased array technology offers the ability to generate multiple sound beams focused at different areas of the weld and at different angles. Also, the ability to generate multiple sound beams allows the weld to be scanned and results in complete coverage.

A phased array ultrasound transducer is typically 2-3 cm long, consisting of 64-128 elements.

What is an advantage of phased array testing? ›

Advantages of Phased Array Ultrasound Testing

Unlike eddy current technology, the surface can be scanned at diverse angles by steering the beam. The steered scanning and optimized controls allow for increased coverage to detect a flaw in the material.

Summary of the Discussion of TFM vs PAUT

The principal advantage of TFM is that the entire image is displayed with focused amplitude, compared to an image produced with PAUT, which is only highly resolved in the focal area of the beam.

PAUT improves weld testing performance over single-probe ultrasonic testing and other NDT methods. Choosing the right ultrasonic testing equipment can increase efficiency, improve test reliability, and provide company managers the peace of mind of knowing that their welds will hold.

25 mm (1.0 in.).

Time of Flight Diffraction (TOFD) is a reliable method of nondestructive ultrasonic testing (UT) used to look for flaws in welds. TOFD uses the time of flight of an ultrasonic pulse to find the location of a reflector.

TOFD – Time-of-Flight Diffraction – is an ultrasonic technique which measures the time of flight of a pulse as it travels from a transmitting probe to a receiving probe. Divergent beams are used and it is necessary to scan the TOFD probe pair over the flaw for the technique to function correctly.

The four main types of ultrasound transducers—linear, curvilinear, phased-array, and intracavitary—differ by crystal arrangement, size, and footprints, which determine their suitability in different imaging applications.

1 (a) of ASME section IX recommends minimum thickness to perform ultrasonic inspection is 6 mm.

Phased Array Transducer Uses

Tube inspection, where multiple probes are often used to detect cracks, find laminar flaws, and measure overall thickness. Forged metal parts, which often require multiple probes focused at different depths to detect small defects in a zonal manner.

What are the principles of phased array inspection? ›

The principle of phased array technology is to activatefor each shot all or some of the transducer elements which, with the adapted delay laws, contribute collectively to the generation of the beam.

An electric current passes through a cable to the transducer and is applied to the crystals, causing them to deform and vibrate. This vibration produces the ultrasound beam. The frequency of the ultrasound waves produced is predetermined by the crystals in the transducer.

Low-frequency inverters have the advantage over high-frequency inverters in two fields: peak power capacity, and reliability. Low-frequency inverters are designed to deal with higher power spikes for longer periods of time than high-frequency inverters.

The near-$900 million structure, operated by the U.S. Missile Defense Agency (MDA), is by far the largest phased-array radar system on Earth.

It is usually another name for a Yagi–Uda antenna. A phased array usually means an electronically scanned array; a driven array antenna in which each individual element is connected to the transmitter or receiver through a phase shifter controlled by a computer.

Advantages of ToFD

ToFD is a single pass operation, not amplitude dependent and very accurate for sizing of vertical defects. The technique is found to be substantially more accurate in sizing the height of defects than conventional pulse echo techniques, which are based on echo amplitude.

Time of flight diffraction (TOFD) is one of the most reliable non-destructive testing methods in testing welds for both pre-service and in-service inspection. An accurate assessment of welds is vital to ensure that the stability and integrity of welded structures is not compromised by defects.

Principle of operation

In a TOFD system, a pair of ultrasonic probes sits on opposite sides of a weld. One of the probes, the transmitter, emits an ultrasonic pulse that is picked up by the probe on the other side, the receiver.

Maurice Silk had invented the TOFD in the late 1970's [13]. TOFD System: The TOFD technique is a fully computerized and automated system able to scan, store, and evaluate indications in terms of height, length, and position with a grade of accuracy never achieved by other ultrasonic techniques [4].

The lateral wave is simply the compression wave travelling parallel to the flat surface. If it is assumed to be travelling parallel to the flat surface (between the Tx and Rx probes) its refracted angle is therefore 90°.

How far can guided waves effectively propagate? ›

Pipes can be considered as one-dimensional structures along which the energy of axisymmetric guided ultrasonic wave modes propagates with little loss of energy, and propagation distances of up to 100 m have been achieved (Cawley et al.

In time-of-flight diffraction (ToFD) systems, a pair of ultrasonic probes are used, sitting on opposite sides of a weld-joint or area of interest. A transmitter probe emits an ultrasonic pulse which is picked up by the receiver probe on the opposite side.