scholarly journals Defect Detection of Aluminium Plates Based on Near-Field Enhancement of Lamb Waves Generated Using an Electromagnetic Acoustic Tranducer

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3529 ◽  
Author(s):  
Zhou ◽  
Zhang ◽  
Xu ◽  
Ren
Keyword(s):  
Lamb Waves ◽  
Near Field ◽  
Broadband Ultrasound Attenuation ◽  
Field Enhancement ◽  
Ultrasonic Waves ◽  
Traditional Methods ◽  
Electromagnetic Acoustic Transducers ◽  
Acoustic Transducers ◽  
Important Means ◽  
Pulse Echo

Ultrasonic testing is an important means to detect defacing defects, such as scratches and cracks, but when the size of these defects is smaller than the wavelength of ultrasonic waves, it is difficult to detect them using traditional methods like the pulse-echo method and broadband ultrasound attenuation method for the diffraction of ultrasonic waves at the defects. Based on the non-contact characteristic of electromagnetic acoustic transducers (EMATs), a transducer for scanning inspection was developed in this paper. The transducer was utilized to detect and measure the depth of the defacing defects on an aluminium plate based on the near-field enhancement of ultrasonic Lamb waves. The results show that the amplitude of the S0 Lamb wave experiences a large enhancement when the transducer is passed over the scratch defects and the enhancement has a clearly positive correlation with the depth of the scratch defects. When the depth increases from 0.1 mm to 0.9 mm, the amplitude of S0 Lamb waves increases from 1.13 times to 2.27 times the S0 Lamb waves received on the aluminium plate without defects. The new method can be utilized to detect the defacing defects on the aluminium plate and get better detection effects than the traditional methods without analyzing the relatively small reflection waves.

Integrating Electromagnetic Acoustic Transducers in a Modular Robotic Gripper for Inspecting Tubular Components

2021 ◽  
Vol 79 (7) ◽  
pp. 715-727
Author(s):  
Hamidreza Nemati ◽  
Fernando Alvidrez ◽  
Ankit Das ◽  
Nihar Masurkar ◽  
Manoj Rudraboina ◽  
...  
Keyword(s):  
Power Plants ◽  
Lamb Waves ◽  
Signal To Noise Ratio ◽  
Ultrasonic Inspection ◽  
Electromagnetic Acoustic Transducers ◽  
Acoustic Transducers ◽  
Main Challenge ◽  
Critical Components ◽  
Spiral Coils ◽  
The Time Domain

Tubular structures are critical components in infrastructure such as power plants. Throughout their life, they are subjected to extreme conditions or suffer from defects such as corrosion and cracks. Although regular inspection of these components is necessary, such inspection is limited by safety-related risks and limited access for human inspection. Robots can provide a solution for automatic inspection. The main challenge, however, lies in integrating sensors for nondestructive evaluation with robotic platforms. As part of developing a versatile lizard-inspired tube inspector robot, in this study the authors propose to integrate electromagnetic acoustic transducers into a modular robotic gripper for use in automated ultrasonic inspection. In particular, spiral coils with cylindrical magnets are integrated into a novel friction-based gripper to excite Lamb waves in thin cylindrical structures. To evaluate the performance of the integrated sensors, the gripper was attached to a robotic arm manipulator and tested on pipes of different outer diameters. Two sets of tests were carried out on both defect-free pipes and pipes with simulated defects, including surface partial cracking and corrosion. The inspection results indicated that transmitted and received signals could be acquired with an acceptable signal-to-noise ratio in the time domain. Moreover, the simulated defects could be successfully detected using the integrated robotic sensing system.

Quantitative Evaluation of an Internal Flaw of a Structural Component Using Electromagnetic Acoustic Transducers

2001 ◽  
Author(s):  
Shinichi Maruyama ◽  
Toshihiko Sugiura ◽  
Akihiro Inoue ◽  
Masatsugu Yoshizawa
Keyword(s):  
Mathematical Model ◽  
Nondestructive Evaluation ◽  
Ultrasonic Waves ◽  
Local Optimum ◽  
Electromagnetic Acoustic Transducers ◽  
Acoustic Transducers ◽  
Time Period ◽  
Internal Flaw ◽  
Inspection Process ◽  
The Mathematical Model

Abstract Electromagnetic acoustic transducers (EMATs) can transmit and detect ultrasonic waves in a conductive specimen out of any contact with it. This process can be given theoretical modeling and formulation based on elastodynamics and electromagnetics. It suggests a possibility of quantitative nondestructive evaluation using EMATs. This research deals with a numerical method of flaw identification from a receiver signal obtained by EMATs. Experimental results of the receiver signals agree well with numerical ones, which verified the mathematical model of the inspection process. Flaw identification is formulated as a problem of parameter optimization. To avoid being trapped in a local optimum, initial parameters were successfully evaluated from the height and the time period of peaks in the receiver signals. Flaw parameters were identified from the receiver signals obtained by numerical simulations and experiments, which verified the method of flaw identification presented here.

scholarly journals Effects of gap thickness and emitter location on the photoluminescence enhancement of monolayer MoS2 in a plasmonic nanoparticle-film coupled system

Nanophotonics ◽  
2020 ◽  
Vol 9 (7) ◽  
pp. 2097-2105
Author(s):  
Xiaozhuo Qi ◽  
Tsz Wing Lo ◽  
Di Liu ◽  
Lantian Feng ◽  
Yang Chen ◽  
...  
Keyword(s):  
Near Field ◽  
Central Area ◽  
Field Enhancement ◽  
Coupled System ◽  
Film Structure ◽  
Plasmonic Nanoparticle ◽  
Emitter Location ◽  
Radiation Properties ◽  
Radiation Enhancement ◽  
Quantum Emitters

AbstractPlasmonic nanocavities comprised of metal film-coupled nanoparticles have emerged as a versatile nanophotonic platform benefiting from their ultrasmall mode volume and large Purcell factors. In the weak-coupling regime, the particle-film gap thickness affects the photoluminescence (PL) of quantum emitters sandwiched therein. Here, we investigated the Purcell effect-enhanced PL of monolayer MoS2 inserted in the gap of a gold nanoparticle (AuNP)–alumina (Al2O3)–gold film (Au Film) structure. Under confocal illumination by a 532 nm CW laser, we observed a 7-fold PL peak intensity enhancement for the cavity-sandwiched MoS2 at an optimal Al2O3 thickness of 5 nm, corresponding to a local PL enhancement of ∼350 by normalizing the actual illumination area to the cavity’s effective near-field enhancement area. Full-wave simulations reveal a counterintuitive fact that radiation enhancement comes from the non-central area of the cavity rather than the cavity center. By scanning an electric dipole across the nanocavity, we obtained an average radiation enhancement factor of about 65 for an Al2O3 spacer thickness of 4 nm, agreeing well with the experimental thickness and indicating further PL enhancement optimization. Our results indicate the importance of configuration optimization, emitter location and excitation condition when using such plasmonic nanocavities to modulate the radiation properties of quantum emitters.

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