Focused Rayleigh wave EMAT for characterisation of surface-breaking defects

Thring, Claire B.; Yang, Fan; Edwards, R. S.

doi:10.1016/j.ndteint.2016.03.002

Cited by 67 publications

(41 citation statements)

References 29 publications

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“…The absolute value was then found, and the power obtained by squaring the result and finding the maximum signal peak after the generation noise. Full details are given in reference [3]. The simulated signal, G, was calculated over the same time range, t, as the real data using…”

Section: Transducer Design and Analysismentioning

confidence: 99%

“…• , and hence any aperture effect is minimal; a smaller aperture angle will lead to changes in the focal beam profile [3].…”

Section: Transducer Design and Analysismentioning

confidence: 99%

“…Rayleigh waves are generally used in one of two modes of operation; looking for reflections returned by surface breaking defects [3], or measuring variations in the transmitted signal traveling from a generation to a detection transEmail address: r.s.edwards@warwick.ac.uk (R.S. Edwards) ducer [4,5].…”

Section: Introductionmentioning

confidence: 99%

“…This has been done in previous work using piezoelectric arrays [16], laser beam optics [17], and laser surface patterning [18], however these techniques can be expensive and complex; the piezoelectric arrays need direct sample contact, and the laser techniques require safety precautions. EMAT focusing has been performed using geometric shaping of the coil to create a shear wave beam spot on the opposite surface of the sample to the probe [19], and a focused surface-wave meander line design has been investigated for operation in reflection mode [20,3]. Geometric focusing means that on, interacting with a defect not at the focal point, wave components are in fact incident at oblique angles, potentially complicating the interaction.…”

Section: Introductionmentioning

confidence: 99%

“…To ensure detection of defects with sub-millimetre depths, high frequencies are required; the EMAT reported in reference [3] was produced for operation at 2 MHz, but this requires a highly complex design. The transducer was very effective at detecting and sizing the surface-breaking profile of machined slot defects down to 1 mm in length.…”

Section: Introductionmentioning

confidence: 99%

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Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Thring

Yang

Edwards

2017

NDT & E International

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Electromagnetic Acoustic Transducers (EMATs) are a useful ultrasonic tool for non-destructive evaluation in harsh environments due to their non-contact capabilities, and their ability to operate through certain coatings. This work presents a new Rayleigh wave EMAT transducer design, employing geometric focusing to improve the signal strength and detection precision of surface breaking defects. The design is robust and versatile, and can be used at frequencies centered around 1 MHz. Two coils are used in transmission mode, which allows the usage of frequency-based measurement of the defect depth. Using a 2 MHz driving signal, a focused beam spot with a width of 1.3 ± 0.25 mm and a focal depth of 3.7 ± 0.25 mm is measured, allowing for defect length measurements with an accuracy of ±0.4 mm and detection of defects as small as 0.5 mm depth and 1 mm length. A set of four coils held under one magnet are used to find defects at orientations offset from normal to the ultrasound beam propagation direction. This EMAT has a range which allows detection of defects which propagate at angles from 16• to 170• relative to the propagation direction over the range of 0 to 180• , and the set up has the potential to be able to detect defects propagating at all angles relative to the wave propagation direction if two coils are alternately employed as generation coils.

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Section: Transducer Design and Analysismentioning

confidence: 99%

“…• , and hence any aperture effect is minimal; a smaller aperture angle will lead to changes in the focal beam profile [3].…”

Section: Transducer Design and Analysismentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Thring

Yang

Edwards

2017

NDT & E International

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On a Highly Reproducible, Broadband Nanocomposite Ultrasonic Film Sensor Fabricated by Ultrasonic Atomization‐Assisted Spray Coating

et al. 2020

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In the last couple of decades, attaching sensors permanently onto in-service engineering structures has been a key strategy for conducting in situ structural integrity assessments. [1-4] In this respect, a wide range of sensors, which include but are not limited to optical fibers, [5,6] piezoelectric transducers, [7-9] electromagnetic acoustic transducers, [10,11] and polyvinylidene fluoride film sensors, [12,13] have been used in practice. However, the existing technologies suffer from various limitations, which include narrow frequency bandwidth, redundant volume and mass, high cost, and stringent requirements on coupling. In pursuit for improved sensing systems, sensors that are lightweight, flexible, cost effective, convenient to fabricate, and sensitive over a broad frequency range have attracted much R&D effort. Carbon nanoparticle-based composite materials, which emerged from recent research, have demonstrated the potential for satisfying the demands of modern sensing systems. The nanostructures of these materials are piezoresistive, such that the overall electrical resistance of a material varies with mechanical deformations. This is mainly attributed to 1) the inherent piezoresistivity of the nanofillers in the material, and changes in 2) the macroscopic resistances and 3) the quantum tunneling resistances between adjacent nanofillers when the distances between the nanofillers change with mechanical deformations. The latter phenomenon is known as the quantum tunneling effect. Wearable strain sensors that are fabricated from carbon nanocomposite materials [14-16] exhibit abundant merits, which include negligible weight, high physical flexibility, remarkable manufacturability, and outstanding sensitivity to microscopic deformations. These attractive features also render carbon nanocomposite materials promising candidates for sensors that are used to monitor conditions of engineering structures. [16-19] It has been shown on many occasions that carbon nanocomposite sensors can be highly sensitive to ultrasonic waves, capable of responding to dynamic strains down to the microscale with frequencies up to hundreds of kilohertz. [20] Also, it is believed that for sensing strains in the ultrasonic regime, the quantum tunneling effect plays the dominant role in determining the piezoresistive responses of the sensors. [21] Nanocomposite ultrasonic sensors are mainly fabricated from three different types of carbon nanofillers, namely, carbon black

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EMAT-Phased Array Inspection of Thick Austenitic Stainless Steel and Dissimilar Metal Welds

Dhayalan

Kumar

Mukhopadhyay

2021

Lecture Notes in Mechanical Engineering

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Focused Rayleigh wave EMAT for characterisation of surface-breaking defects

Cited by 67 publications

References 29 publications

Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

Multi-coil focused EMAT for characterisation of surface-breaking defects of arbitrary orientation

On a Highly Reproducible, Broadband Nanocomposite Ultrasonic Film Sensor Fabricated by Ultrasonic Atomization‐Assisted Spray Coating

EMAT-Phased Array Inspection of Thick Austenitic Stainless Steel and Dissimilar Metal Welds

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