Helical Mode Guided Waves in Pipe Observed by Electromagnetic Acoustic Transducer Array

2018 ◽  
Vol 54 (22) ◽  
pp. 38
Author(s):  
Jingjie ZHOU
Keyword(s):  
Guided Waves ◽  
Electromagnetic Acoustic Transducer ◽  
Transducer Array ◽  
Acoustic Transducer ◽  
Helical Mode

An improved design of shear horizontal guided wave electromagnetic acoustic transducer

2020 ◽  
Vol 62 (8) ◽  
pp. 494-497
Author(s):  
Xu Zhang ◽  
Sheng Feng ◽  
Jun Tu ◽  
Xiaochun Song
Keyword(s):  
Guided Waves ◽  
Cost Effective ◽  
Guided Wave ◽  
Experimental Investigations ◽  
Electromagnetic Acoustic Transducer ◽  
Rectangular Array ◽  
Acoustic Transducers ◽  
Acoustic Transducer ◽  
Improved Design ◽  
Shear Horizontal

This work proposes the use of a Halbach magnet structure to enhance the generation efficiency of shear horizontal (SH) guided waves on a plate. SH waves are normally generated using periodic permanent magnet (PPM) electromagnetic acoustic transducers (EMATs). Two PPM configurations are designed using a Halbach magnet array and the enhancements of the static magnetic fields of the two magnet arrays are validated by the finite element method, indicating that these configurations can increase the peak flux density compared with the conventional configuration. Numerical analysis and experimental investigations indicate that a racetrack coil combined with either a rectangular or triangular Halbach magnet array can enhance the amplitude of the SH guided wave by factors of ∼1.2 and ∼1.1, respectively, and that the rectangular array performs better and is more cost effective.

scholarly journals Simulation of an Electromagnetic Acoustic Transducer Array by Using Analytical Method and FDTD

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Yuedong Xie ◽  
Sergio Rodriguez ◽  
Wenbo Zhang ◽  
Zenghua Liu ◽  
Wuliang Yin
Keyword(s):  
Analytical Solution ◽  
Time Domain ◽  
Fdtd Method ◽  
Force Density ◽  
Large Radius ◽  
Electromagnetic Acoustic Transducer ◽  
Transducer Array ◽  
Ultrasound Waves ◽  
Acoustic Transducer ◽  
Frequency Regime

Previously, we developed a method based on FEM and FDTD for the study of an Electromagnetic Acoustic Transducer Array (EMAT). This paper presents a new analytical solution to the eddy current problem for the meander coil used in an EMAT, which is adapted from the classic Deeds and Dodd solution originally intended for circular coils. The analytical solution resulting from this novel adaptation exploits the large radius extrapolation and shows several advantages over the finite element method (FEM), especially in the higher frequency regime. The calculated Lorentz force density from the analytical EM solver is then coupled to the ultrasonic simulations, which exploit the finite-difference time-domain (FDTD) method to describe the propagation of ultrasound waves, in particular for Rayleigh waves. Radiation pattern obtained with Hilbert transform on time-domain waveforms is proposed to characterise the sensor in terms of its beam directivity and field distribution along the steering angle, which can produce performance parameters for an EMAT array, facilitating the optimum design of such sensors.

scholarly journals Nondestructive Inspection of Corrosion and Delamination at the Concrete-Steel Reinforcement Interface

2002 ◽  
Author(s):  
Tri Miller ◽  
Christopher J. Hauser ◽  
Tribikram Kundu
Keyword(s):  
Guided Waves ◽  
Guided Wave ◽  
Ultrasonic Guided Waves ◽  
Reinforcing Steel ◽  
Electromagnetic Acoustic Transducer ◽  
Long Distance ◽  
Steel Bar ◽  
Acoustic Transducer ◽  
Steel Bars ◽  
Aging Infrastructure

This paper explores the feasibility of detecting and quantifying corrosion and delamination at the interface between reinforcing steel bar and concrete using ultrasonic guided waves. The problem of corrosion and delamination of the reinforcing steel in the aging infrastructure has increased significantly in the last three decades and is likely to keep on increasing. Ultrasonic cylindrical guided waves that can propagate a long distance along the reinforcing steel bar are found to be sensitive to the interface conditions between steel bar and concrete. Ultrasonic transducers are used to launch and detect cylindrical guided waves along the steel bar. The traditional ultrasonic testing methods, for instance the pulse-echo method, where reflection, transmission, and scattering of longitudinal waves are used for detecting large voids in concrete, are not very efficient for detecting corrosion and delamination at the interface between concrete and steel bar. For this study four sets of specimens were prepared. They are rebars and plain steel bars with corrosion and physical separation. Transducers used during the experiment are the Electromagnetic Acoustic Transducer (EMAT) and the Piezoelectric Transducer (PZT). The experiment suggests that the guided wave inspection technique is feasible for the health monitoring of reinforced concrete structures. It also reveals that the ultrasonic guided waves are sensitive to the type of steel used and to the rib patterns on the reformed steel bars.

Shear horizontal circumferential wave EMAT design for pipeline inspection based on FEM

2020 ◽  
Vol 64 (1-4) ◽  
pp. 913-919
Author(s):  
Xu Zhang ◽  
Jiang Cheng ◽  
Gongzhe Qiu ◽  
Jun Tu ◽  
XiaoChun Song ◽  
...  
Keyword(s):  
Finite Element ◽  
Piezoelectric Transducer ◽  
Guided Waves ◽  
Element Model ◽  
Transduction Efficiency ◽  
Electromagnetic Acoustic Transducer ◽  
Pipeline Inspection ◽  
Acoustic Transducer ◽  
Circumferential Wave ◽  
Shear Horizontal

The electromagnetic acoustic transducer (EMAT) is widely used in In-Line Inspection of gas pipeline. However, the transduction efficiency of the EMAT transmitter is lower compared with the traditional piezoelectric transducer and needs improving. To enhance the amplitude of the received signal, an improved periodic-permanent-magnet EMAT is provided as well as its construction method to generate shear horizontal guided waves propagating in the circumferential direction. By designing a racetrack coil and magnetic array with the same radian of the annular pipeline, the EMAT is more suitable to generate the circumferential wave in the pipeline. The performance of the EMAT transmitter has been assessed with the validated finite element model.

Oil-Tank Weld Detection Using EMAT

2017 ◽  
Vol 14 (02) ◽  
pp. 1750008 ◽  
Author(s):  
Li Chen ◽  
Wang-Rim Choi ◽  
Jeong-Gu Lee ◽  
Yi-Gon Kim ◽  
Hong-Sik Moon ◽  
...  
Keyword(s):  
Elastic Waves ◽  
Guided Waves ◽  
Ferromagnetic Material ◽  
Transduction Efficiency ◽  
Sh Wave ◽  
Electromagnetic Acoustic Transducer ◽  
Acoustic Transducer ◽  
Oil Tank ◽  
Non Destructive ◽  
Shear Horizontal

Tanks are typically used for the storage of oil by the petrochemical industry, and the storage quality is largely determined by the safety of the equipment. Recently, Electromagnetic Acoustic Transducer (EMAT) technology has been the focus of many non-destructive examinations, as EMATs can generate elastic waves without contact, thereby making it easy to carry out the process of detection. The Shear Horizontal (SH)-guided waves that are generated by an EMAT are modeled in a plate made of ferromagnetic material, and this is of particular interest regarding the testing of welded structures. This paper provides an EMAT-sensor design that can be used to find cracks in the welds of a tank whereby the need for people to climb onto the tank is removed; furthermore, regarding cases where the amplitude signal of the SH-wave EMATs is too low, a simulation is used in this paper to propose a method that improves the transduction efficiency.

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