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.

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.

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.

As is the case with conventional transducers, phased array probes may be designed for direct contact use, as part of an angle beam assembly with a wedge, or for immersion use with sound coupling through a water path. Transducer frequencies are most commonly in the range from 2 MHz to 10 MHz.

The advantages of phased array ultrasonic testing (PAUT) include faster scans, a higher probability of detecting flaws and anomalies and the best possibility of performing an inspection. The PAUT method of non-destructive testing uses multiple beams to scan an asset.

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.

What is the difference between PAUT and TFM? ›

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.

25 mm (1.0 in.).

Time of flight diffraction is an advanced non-destructive testing method used for weld inspection. 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.

In ultrasonic testing, an inspector will use a probe or some other kind of transducer to send sound waves through the material they want to test. If there are no defects in the material, the sound waves will pass through it, but if the sound waves hit a defect they will bounce off of it, indicating its presence.

Time of flight diffraction (TOFD) is a highly sensitive and accurate method for the non-destructive testing (NDT) of welds for defects. The TOFDPROOF project adopted an integrated approach for applying TOFD to the detection and sizing of defects in carbon steel welds at the manufacturing stage.

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].

A single TOFD setup is limited to a maximum thickness of about 30 - 40 mm. For thicker components, two zones with two PCS are used. They are called upper and lower TOFD zones. As the component gets thicker lower frequency probes such as 5 MHz 6 mm diameter are used for the lower zone.

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.

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.

The three types of phased array antennas are 1) linear array, 2) planar array, and 3) frequency scanning array.

What are the five controls to design an array antenna? ›

MIMO (Multiple Input Multiple Output) antennas operate by breaking high data rate signals into multiple lower data rate signals in Tx mode that are recombined at the receiver. Beamforming arrays are inherently different from MIMO in that the multiple columns of dipoles work together to create a single high gain signal.

Phased Array Ultrasonic Testing (PAUT), also known as phased array UT, is an advanced non-destructive inspection technique that uses a set of ultrasonic testing (UT) probes made up of numerous small elements.

Most ultrasonic testing is available within 400 kHz to 25 MHz. These vibrations are beyond the audible range and propagate in the test material as waves of particle vibrations. Sound beams of all frequencies can penetrate fine-grained material without difficulty.

Phased Array transducer has a small footprint and low frequency (its central frequency is 2Mhz – 7.5Mhz).

Disadvantages of Phased Array Ultrasound Testing

While PAUT has a wide range of abilities, it's not a preferred testing method for the detection of surface cracks, metal fatigue, or bolt hole inspections compared to eddy current testing.

Phased array transducers are used for various NDT inspections, including: Tube inspection, where multiple probes are often used to detect cracks, find laminar flaws, and measure overall thickness.

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.

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.

Both PAUT and RT are capable of discontinuity, or flaw detection, with high POD, RT has a limited ability to detect weld defects—e.g., lack of fusion. And while more capable with smaller, volumetric flaws, PAUT enables penetration of much thicker materials.

How many elements are in a phased array transducer? ›

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

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.

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 is an advanced non-destructive testing method used for weld inspection. 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.

Basic principle of TOFD. The most significant distinction between TOFD and the other UT methods is that it monitors only forward-scattered diffracted energies from the tips of defects rather than reflected ultrasonic energies. Two wide beam angle probes are used in transmitter-receiver mode.

Ultrasonic testing can be performed using two basic methods – pulse-echo and through-transmission.

Several wave modes of vibration are used in ultrasonic inspection. The most common are longitudinal, shear, and Rayleigh (surface) waves. Ultrasonic waves are very similar to light waves in that they can be reflected, refracted, and focused.

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°.

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 eddy current testing, a coil carrying an AC current is placed close to the specimen surface, or around the specimen. The current in the coil generates circulating eddy currents in the specimen close to the surface and these in turn affect the current in the coil by mutual induction.