The relative merits of three different periodic permanent magnet (PPM) configurations are investigated for the generation of SH0 waves with a Lorentz-force electromagnetic acoustic transducer (EMAT) on a 60-mm diameter aluminum pipe. Such transducers are often used for checking the integrity of pipelines. It was found that minimizing lift-off by using magnets machined to the same curvature as the pipe increased the magnitude of the generated wave by over 70%, compared to the use of a PPM with a single planar surface. A less expensive and more versatile alternative is to use a PPM for which the two lines of magnets are angled with respect to each other to realize closer average proximity to the pipe surface. Numerical simulations and experiments indicated that the amplitude of a SH0 wave with this magnet configuration would still be approximately 60% higher than the reference case of a PPM with a single planar surface.
 M. Hirao and H. Ogi. EMATs for Science and Industry: Noncontacting Ultrasound Measurements. Kluwer Academic Publishers, Boston (2003).
 L. Placidi, U. Andreaus, A. D. Corte, and T. Lekszycki, Angew. Math. Phys. 66:3699 (2015). doi:10.1007/s00033-015-0588-9.
 U. Andreaus, F. Dell’Isola, I. Giorgio, L. Placidi, T. Lekszycki, and N. L. Rizzi. Int. J. Eng. Sci. 108:34 (2016). doi: 10.1016/j.ijengsci.2016.08.0.
 H. Ogi, M. Hirao, and T. Honda. J. Acoust. Soc. Am. 98(1):458–464 (1995).
 R. Ribichini, F. Cegla, P. B. Nagy, and P. Cawley. IEEE Trans. Ultrason., Ferroelect., Freq. Control 58:12 (2011).
 J. Isla and F. Cegla. IEEE Trans. Ultrason., Ferroelect., Freq. Control 63:8 (2016).
 Y. Wang, X. Wu, P. Sun, and J. Li. Sensors 15:3471–3490 (2015).
 J. Flora, M. Ali, and G. Powers. United States of America Patent US 7165453 B2 (January 23, 2007).
 S. K. Advani. An Ultrasonic Guided Wave Inspection System for Hard to Access Civil Structures. The Penn. State University Thesis Collections (2009).
 N. Andruschak, I. Saletes, T. Filleter, and A.N. Sinclair. NDT and E Int. 75 (2015).
 D. Ensminger and F. B. Stulen. Ultrasonics: Data, Equations and Their Practical Uses. CRC Press, Boca Raton, FL (2009).
 R. Ribichini. Modelling of Electromagnetic Acoustic Transducers. Imperial College London Thesis Collection (2011).
 K. J. Magnetics Inc, Magnet Grades [Online]. Available at www.kjmagnetics.com/bhcurves.asp (accessed 20 December 2016).
 K. Mirkhani, C. Chaggares, C. Masterson, M. Jastrzebski, T. Dusatko, A. Sinclair, R. Jafari Shapoorabadi, A. Konrad, and M. Papini. NDT and E. Int. 37:181–193 (2004).
 J. L. Rose. In Ultrasonic Guided Waves in Solid Media. pp. 188–192 (2014).
24 Page Views
0 PDF Downloads
0 Facebook Shares