A New Electromagnetic Acoustic Transducer Design for Generating and Receiving S0 Lamb Waves in Ferromagnetic Steel Plate

Electromagnetic acoustic transducers (EMATs) are non-contact, ultrasonic transducers that are usually kept within 5 mm from the sample surface to obtain a sufficient signal-to-noise ratio (SNR). One important issue associated with operation on a ferromagnetic plate is that the strong attraction force from the magnet can affect measurements and make scanning difficult. This paper investigates a method to generate fundamental, symmetric Lamb waves on a ferromagnetic plate. A coil-only, low-weight, generation EMAT is designed and investigated, operating at lift-offs of over 5 mm. Another design of an EMAT is investigated using a rectangular magnet with a much higher lift-off than the coil, of up to 19 mm. This results in a much lower force between the EMAT and sample, making scanning the EMAT much easier.

[1]  Steve Dixon,et al.  Weld defect detection using PPM EMAT generated shear horizontal ultrasound , 2015 .

[2]  Steve Dixon,et al.  Ultrasonic texture measurement of sheet metals: an integrated system combining Lamb and shear wave techniques , 2005 .

[3]  M. H. Rosli,et al.  In-plane and out-of-plane measurements of Rayleigh waves using EMATs for characterising surface cracks , 2012 .

[4]  Kang Zhang,et al.  Influence of the Lift-Off Effect on the Cut-Off Frequency of the EMAT-Generated Rayleigh Wave Signal , 2014, Sensors.

[5]  R. B. Thompson,et al.  Mechanisms of electromagnetic generation and detection of ultrasonic Lamb waves in iron‐nickel alloy polycrystals , 1977 .

[6]  S Dixon,et al.  Detection of cracks in metal sheets using pulsed laser generated ultrasound and EMAT detection. , 2011, Ultrasonics.

[7]  Peter Cawley,et al.  Study and comparison of different EMAT configurations for SH wave inspection , 2011, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[8]  Matthew Fleming,et al.  Circumferential guided wave EMAT system for pipeline screening using shear horizontal ultrasound , 2017 .

[9]  Tomohiro Yamasaki,et al.  Effect of applied stresses on magnetostriction of low carbon steel , 1996 .

[10]  H. Ogi,et al.  EMATs for Science and Industry: Noncontacting Ultrasonic Measurements , 2010 .

[11]  Wei Zhao,et al.  Study on the Lift-off Effect of EMAT , 2009 .

[12]  Wamadeva Balachandran,et al.  A study of the transduction mechanisms of electromagnetic acoustic transducers (EMATs) on pipe steel materials , 2015 .

[13]  Koichi Mizutani,et al.  Development of an Electromagnetic Acoustic Transducer with Multi-Wavelength for Lamb Wave , 2002 .

[14]  Xinjun Wu,et al.  Enhancement of the Excitation Efficiency of a Torsional Wave PPM EMAT Array for Pipe Inspection by Optimizing the Element Number of the Array Based on 3-D FEM , 2015, Sensors.

[15]  Lei Kang,et al.  3-D modeling and analysis of meander-line-coil surface wave EMATs , 2012 .

[16]  Chao Zhang,et al.  Enhancement of ultrasonic signal using a new design of Rayleigh-wave electromagnetic acoustic transducer , 2017 .

[17]  Steve Dixon,et al.  High temperature thickness measurements of stainless steel and low carbon steel using electromagnetic acoustic transducers , 2014 .

[18]  R. Murayama.  Driving mechanism on magnetostrictive type electromagnetic acoustic transducer for symmetrical vertical-mode Lamb wave and for shear horizontal-mode plate wave , 1996 .

[19]  C. Davis,et al.  Development of an automated non-contact ultrasonic texture measurement system for sheet metal , 2004 .

[20]  Matthias Seher,et al.  Model-Based Design of Low Frequency Lamb Wave EMATs for Mode Selectivity , 2015 .

[21]  P A Petcher,et al.  Shear horizontal (SH) ultrasound wave propagation around smooth corners. , 2014, Ultrasonics.

[22]  Riichi Murayama,et al.  Study of driving mechanism on electromagnetic acoustic transducer for Lamb wave using magnetostrictive effect and application in drawability evaluation of thin steel sheets , 1999 .

[23]  Peter B. Nagy,et al.  Corrosion and erosion monitoring in plates and pipes using constant group velocity Lamb wave inspection. , 2014, Ultrasonics.

[24]  Rachel S. Edwards,et al.  Enhancement of the Rayleigh wave signal at surface defects , 2004 .

[25]  Peter Cawley,et al.  Quantitative modeling of the transduction of electromagnetic acoustic transducers operating on ferromagnetic media , 2010, IEEE Transactions on Ultrasonics, Ferroelectrics and Frequency Control.

[26]  S B Palmer,et al.  Wideband low frequency generation and detection of Lamb and Rayleigh waves using electromagnetic acoustic transducers (EMATs). , 2004, Ultrasonics.

[27]  Hirotsugu Ogi,et al.  Increase of Efficiency of Magnetostriction SH-Wave Electromagnetic Acoustic Transducer by Angled Bias Field: Piezomagnetic Theory and Measurement , 2003 .

[28]  Steve Dixon,et al.  Frequency dependent directivity of periodic permanent magnet electromagnetic acoustic transducers , 2014 .

[29]  Songling Huang,et al.  A New Omni-Directional EMAT for Ultrasonic Lamb Wave Tomography Imaging of Metallic Plate Defects , 2014, Sensors.