Study of magnetic pole materials for static magnetic field and dynamic magnetic field that compose an electromagnetic acoustic transducer for Lamb waves using the magnetostriction effect

2021 ◽  
pp. 113294
Author(s):  
Riichi Murayama ◽  
Yuta Akizuki
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field ◽  
Lamb Waves ◽  
Magnetic Pole ◽  
Electromagnetic Acoustic Transducer ◽  
Acoustic Transducer ◽  
Dynamic Magnetic Field

Stress measurement based on magnetostrictive characteristic parameters

2021 ◽  
Vol 63 (5) ◽  
pp. 283-288
Author(s):  
Entao Yao ◽  
Fei Han ◽  
Ping Wang ◽  
Yuan Zhang
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Static Magnetic Field ◽  
Stress Measurement ◽  
Maximum Relative Error ◽  
Electromagnetic Acoustic Transducer ◽  
Wide Range ◽  
The Relationship ◽  
Non Destructive

Non-destructive testing (NDT) involving stress measurement has found a wide range of applications in rail, pipeline, bridge and other engineering areas and it is therefore necessary to find a method to measure stress. In this paper, a non-destructive method is proposed to measure stress by observation of the magnetostrictive properties of the objects. Stress in the elastic range is applied to the ferromagnetic material, changing its lattice, while stress in the plastic range changes its microstructure. These are the reasons for the magnetostrictive coefficient variation of the material. An experimental platform was set up, using a cantilever beam with a strain gauge, to study the relationship between the SH wave, the static magnetic field strength and the applied uniaxial stress. The curve obtained shows the relationship between the amplitude of the electromagnetic acoustic transducer (EMAT) signal and the static magnetic field strength. The magnetostrictive parameters, sensitive to stress, were extracted from the curve. This method is verified through trials on test samples with a maximum relative error between experimental and predicted values of 8.06%.

scholarly journals Modes Control of Lamb Wave in Plates Using Meander-Line Electromagnetic Acoustic Transducers

2020 ◽  
Vol 10 (10) ◽  
pp. 3491 ◽  
Author(s):  
Yinghong Zhang ◽  
Zhenghua Qian ◽  
Bin Wang
Keyword(s):  
Magnetic Field ◽  
Lamb Wave ◽  
Lamb Waves ◽  
Single Mode ◽  
Plate Surface ◽  
Electromagnetic Acoustic Transducer ◽  
Bias Magnetic Field ◽  
Low Frequencies ◽  
Aluminum Plates ◽  
Meander Line

The multimode and dispersion characteristics of Lamb waves make them difficult to apply to nondestructive evaluation. This paper presents a paired configuration of a meander-line coil electromagnetic acoustic transducer (EMAT) to generate a single-mode symmetric and antisymmetric Lamb wave in aluminum plates. In the paired structure, the bias magnetic field of the EMAT that generates symmetric mode Lamb waves is perpendicular to the plate surface, while the bias magnetic field of the EMAT that generates antisymmetric Lamb waves is parallel to the plate surface. The symmetric and antisymmetric exciting forces generated by these two EMATs are consistent with the dispersion equations of single symmetric and antisymmetric Lamb wave modes, respectively. The numerical simulations and experiments verified that the presented paired configurations of meander-line coil EMATs can effectively control the generation of single-mode Lamb waves at low frequencies.

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.

Decreased chemotaxis of human peripheral phagocytes exposed to a strong static magnetic field

2004 ◽  
Vol 91 (1) ◽  
pp. 59-65 ◽  
Author(s):  
S Sipka ◽  
I Szöllősi ◽  
Gy Batta ◽  
Gy Szegedi ◽  
Á Illés ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Static Magnetic Field
Sign in / Sign up

Export Citation Format

Share Document