Development of an omni-directional magnetic-concentrator-type electromagnetic acoustic transducer

Liu, Zenghua; Deng, Liming; Zhang, Yongchen; Li, Aili; Wu, Bin; He, Chao

doi:10.1016/j.ndteint.2019.102193

Cited by 21 publications

(8 citation statements)

References 25 publications

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“…Many scholars have conducted research on this issue. Liu et al [ 23 ] proposed a magnetic-concentrator-type EMAT configuration to avoid the problems caused by the multimode characteristics of Lamb waves. Sun et al [ 24 ] enhanced A 0 mode Lamb waves and suppressed S 0 mode Lamb waves by optimizing the permanent magnet configuration.…”

Section: Introductionmentioning

confidence: 99%

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A0 Mode LAMB Wave EMATs

Yang

Zhang

et al. 2023

Materials

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Aluminum/rigid polyurethane foam composite plates (ARCPs) are widely used for thermal insulation. The interface debonding generated during manufacturing degrades the thermal insulation performance of an ARCP. In this study, the debonding of an ARCP, a composite plate with a porous and damped layer of rigid polyurethane foam (RPUF), was detected using A0 mode Lamb wave electromagnetic acoustic transducers (EMATs). The low energy transmission coefficient at the interface caused by the large acoustic impedance difference between aluminum and RPUF made the detection difficult. Based on these structural characteristics, an A0 mode Lamb wave with large out-of-plane displacement was used to detect the debonding. EMATs are preferred for generating A0 mode Lamb waves due to their advantages of being noncontact, not requiring a coupling agent, and providing convenient detection. A finite element simulation model considering the damping of the RPUF layer, the damping of the PU film at the interface, and the bonding stiffness of the interface was established. The simulation results indicated that the Lamb wave energy in the aluminum plate transmits into the RPUF layer in small amounts. However, the transmitted energy rapidly attenuated and was not reflected into the aluminum plate, as the RPUF layer was thick and highly damped. Therefore, energy attenuation was evident and could be used to characterize the debonding. An approximately linear relationship between the amplitude of the received signals and the debonding length was obtained. Experiments were performed on an ARCP using EMATs, and the experimental results were in good agreement with the simulation results.

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Section: Introductionmentioning

confidence: 99%

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A0 Mode LAMB Wave EMATs

Yang

Zhang

et al. 2023

Materials

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“…The results revealed that both the S0 and A0 mode Lamb waves were improved to certain extents [ 13 ]. A magnetic concentrator was added between the magnet and coil, which promoted the ability of EMATs for defect inspection [ 26 , 27 ].…”

Section: Introductionmentioning

confidence: 99%

A Lorentz Force EMAT Design with Racetrack Coil and Periodic Permanent Magnets for Selective Enhancement of Ultrasonic Lamb Wave Generation

Guo

Zhu

Qiu

et al. 2022

Sensors

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This article proposes an electromagnetic acoustic transducer (EMAT) for selectively improving the purity and amplitude of ultrasonic Lamb waves in non-ferromagnetic plates. The developed EMAT consists of a racetrack coil and a group of periodic permanent magnets (PPMs). Two-dimensional finite element simulations and experiments are implemented to analyze the working mechanism and performance of the PPM EMAT. Thanks to the specific design, the eddy currents increase with increasing wire density and the directions of the magnetic fields and Lorentz forces alternate according to the polarities of the magnet units. Wires laid uniformly beneath the magnets, and the gaps between adjacent magnets generate tangential and normal Lorentz forces, resulting in-plane (IP) and out-of-plane (OP) displacements, respectively. The constructive interference occurs when the wavelength of the generated Lamb wave is twice the spacing of the magnets, leading to large amplitudes of the targeted ultrasonic Lamb waves. Therefore, the PPM EMAT is capable of generating pure symmetric or antisymmetric mode Lamb waves at respective frequencies. The results prove that the developed PPM EMAT can generate pure either S0 or A0 mode Lamb waves at respective frequencies. The increase in wire width and wire density further increases the signal amplitudes. Compared with the case of conventional meander-line-coil (MLC) EMAT, the amplitudes of the A0 and S0 mode Lamb waves of our PPM EMAT are increased to 880% and 328%, respectively.

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“…Further problems arise from the need to move the emitter/receiver in multiple spatial directions with respect to the component: at least one direction is represented by the normal to the piece surface, which is necessary for the coupling between structure and sensor. For these reasons, the number of application areas is constantly expanding in which non-contact ultrasonic systems are well-established, like optical technologies, Electro-Magnetic Transducers (EMATs) [7,8,9,10] or more consolidated instruments like air-coupled piezoelectric transducers [11,12]. In this context, the optical excitation and ultrasonic detection systems are extremely performing, because of the high transduction efficiency compared to other devices [13,14,15,16].…”

Section: Introductionmentioning

confidence: 99%

Line Scanning with Gas-Coupled Laser Acoustic Detection

Gulino

Bruzzi

Vangi

2022

J. Phys.: Conf. Ser.

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The Gas-Coupled Laser Acoustic Detection (GCLAD) is an optical technique for ultrasonic detection based on the deviation that a laser beam sustains when travelling in a fluid that features refractive index fluctuations. If the laser beam is perpendicular to the wave propagation direction, the technique enables simultaneous detection of direct waves in mechanical components and eventual echoes from defects to be achieved. The technique is applied to the inspection of elements predominantly extending in one/two dimensions as bars and axisymmetric pieces, exploiting a signal enhancement effect occurring in defects’ proximity. The phenomenon, namely constructive interference between wave crests of a direct Rayleigh ultrasound and those associated with reflections on a defect flank, is first illustrated numerically. The effect of parameters like the angle between wave propagation direction and source-receiver distance on the GCLAD sensitivity is then experimentally highlighted. The technique is finally implemented to B-scan a steel plate with 1 mm wide, 20 mm long, and 3 mm deep surface defects. Since the GCLAD probe laser beam insists on an entire line, defects present on that line can be identified without moving the device along such direction. This reduces the monitoring time compared to techniques leveraging on traditional air-coupled transducers or more sophisticated methods (Scanning Laser Source).

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Development of an omni-directional magnetic-concentrator-type electromagnetic acoustic transducer

Cited by 21 publications

References 25 publications

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A0 Mode LAMB Wave EMATs

Debonding Detection in Aluminum/Rigid Polyurethane Foam Composite Plates Using A0 Mode LAMB Wave EMATs

A Lorentz Force EMAT Design with Racetrack Coil and Periodic Permanent Magnets for Selective Enhancement of Ultrasonic Lamb Wave Generation

Line Scanning with Gas-Coupled Laser Acoustic Detection

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