An electromagnetic acoustic transducer with electromagnetic pulse restraining

2021 ◽  
Vol 63 (2) ◽  
pp. 111-117
Author(s):  
Wu Dehui ◽  
Yang Jiaxin ◽  
Chen Wenxiong ◽  
Wang Teng
Keyword(s):  
Magnetic Field ◽  
Electromagnetic Pulse ◽  
Design Method ◽  
Signal To Noise Ratio ◽  
Ultrasonic Waves ◽  
Alternating Magnetic Field ◽  
Electromagnetic Acoustic Transducer ◽  
Destructive Testing ◽  
Acoustic Transducer ◽  
Magnetic Field Model

Electromagnetic acoustic transducers (EMATs) are widely used in non-destructive testing (NDT). However, when ultrasonic waves are excited, the transmitting coil generates a strong alternating magnetic field, resulting in the generation of an electromagnetic pulse. To address this problem, an EMAT with electromagnetic pulse restraining is presented in this paper. First, the cause of the electromagnetic pulse is investigated. Second, the conditions for restraining the electromagnetic pulse using the new transmitting coil are analysed. Finally, the design method for the new transmitting coil is provided through evaluation of the magnetic field model of the new transmitting coil. The experimental results demonstrate that the new transmitting coil has a significant effect on the excitation of ultrasonic waves in the tested material and the restraining of electromagnetic pulses. Therefore, the method proposed in this study can self-compensate for the strong alternating magnetic field generated by the transmitting coil, reduce the interference of the electromagnetic pulse with the ultrasonic wave and improve the signal-to-noise ratio (SNR) of EMATs.

Исследование выявляемости поверхностных объемных дефектов при ультразвуковом контроле с применением волн Рэлея, генерируемых электромагнитно-акустическим преобразователем

2021 ◽  
pp. 22-30
Author(s):  
Н.П. Алешин ◽  
Н.В. Крысько ◽  
А.Г. Кусый ◽  
С.В. Скрынников ◽  
Л.Ю. Могильнер
Keyword(s):  
Pitting Corrosion ◽  
Signal To Noise Ratio ◽  
Ultrasonic Method ◽  
Low Carbon Steel ◽  
Statistical Processing ◽  
Probability Of Detection ◽  
Low Carbon ◽  
Electromagnetic Acoustic Transducer ◽  
Destructive Testing ◽  
Acoustic Transducer

The paper presents the study of the "pitting corrosion" surface operational flaws detectability by the ultrasonic method of non-destructive testing. The possibility of using Rayleigh surface waves excited by an electromagnetic acoustic transducer (EMAT) for these purposes is considered. Blind vertical drills of various diameters and depths were used as artificial defects to simulate these flaws in low-carbon steel specimens. Based on the measurement results, the dependences of the amplitude of the received signals on the drilling parameters were plotted. During the statistical processing of the results, the signal-to-noise ratio was taken into account upon excitation of the Rayleigh wave using EMAT on defect-free areas of the samples. To construct curves of probability of detection (PoD), optimal models of the amplitudes distribution are determined. Under the conditions of the experiments carried out using the constructed PoD curves, conclusions were made about the minimum dimensions of a "pitting corrosion" type defect, detected with a probability of 90 %, taking into account the confidence interval of 95%, and about the possibility of adjusting the ultrasonic testing parameters using signals reflected from vertical drills.

scholarly journals Physic perspective fusion of electromagnetic acoustic transducer and pulsed eddy current testing in non-destructive testing system

2020 ◽  
Vol 378 (2182) ◽  
pp. 20190608
Author(s):  
Wei Guo ◽  
Bin Gao ◽  
Gui Yun Tian ◽  
Dan Si
Keyword(s):  
Eddy Current ◽  
Surface Defects ◽  
Eddy Current Testing ◽  
Non Destructive Testing ◽  
Electromagnetic Acoustic Transducer ◽  
Destructive Testing ◽  
Current Testing ◽  
Pulsed Eddy Current ◽  
Acoustic Transducer ◽  
Non Destructive

Comprehensive non-destructive testing (NDT) for pipelines is a critical and challenging task. This paper proposes a novel physic perspective fusion NDT method of electromagnetic acoustic transducer (EMAT) and pulsed Eddy current testing (PECT) for detecting hybrid defects. This transceiver-integrated fusion sensor structure can simultaneously excite ultrasound and pulsed eddy current. Therefore, the generated ultrasound is applied to detect deep defects, while the eddy current detects surface defects. The theoretical derivation of EMAT and PECT fusion mechanism has been developed for analysis and interpretation of the results. In addition, numerical simulation on the detection of hybrid defects including surface defects with different width, depth and multiple bottom-thinning defects has been conducted. Experiments on both ferromagnetic and non-ferromagnetic material verify the feasibility of composite detection. Finally, tests have been validated on pipeline with weld defects, and the results show that the composite inspection method is capable of monitoring thickness variations and inspecting surface defects. This article is part of the theme issue ‘Advanced electromagnetic non-destructive evaluation and smart monitoring’.

Исследование выявляемости поверхностных плоскостных дефектов ультразвуковым методом с применением волн Рэлея

2021 ◽  
Vol 6 ◽  
pp. 26-34
Author(s):  
Н.П. Алешин ◽  
Н.В. Крысько ◽  
С.В. Скрынников ◽  
А.Г. Кусый
Keyword(s):  
Experimental Studies ◽  
Signal Amplitude ◽  
Probability Of Detection ◽  
Non Destructive Testing ◽  
Electromagnetic Acoustic Transducer ◽  
Destructive Testing ◽  
Testing Method ◽  
Acoustic Transducer ◽  
Non Destructive ◽  
Planar Flaw

The issues of detecting operational surface planar flaws by the ultrasonic non-destructive testing method with the use of Rayleigh surface waves generated by an electromagnetic-acoustic transducer are considered. The paper presents experimental studies of planar defects detection, simulated by an artificial reflector of the "notch" type with different width, depth and angle of inclination. The dependences of the signal amplitude on the listed parameters are constructed and their character was estimated. The optimal amplitude models for constructing the probability of detection curves (PoD) have been determined. A conclusion is made about the minimum dimensions of an operational planar flaw detected by the considering method with a probability of 90%, taking into account the confidence interval of 95%.

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