Line-focusing electromagnetic acoustic transducers for the detection of slit defects

1999 ◽  
Vol 46 (2) ◽  
pp. 341-346 ◽  
Author(s):  
H. Ogi ◽  
M. Hirao ◽  
T. Ohtani
Keyword(s):  
Electromagnetic Acoustic Transducers ◽  
Acoustic Transducers

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.

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.

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