Bragg Reflection Of BG And Rayleigh Waves In A Magnetoelectroelastic Substrate With A Periodically Metal Electrode Perturbed Surface

Magnetoelectroelastic?MEE?material is a kind of new-style smart composite with mechanical,electrical and magnetical multi-field coupling effects.Especially,its unique magneto-electric?ME?effect strongly supports the realization and application of MEE surface acoustic wave?SAW?devices.Most of SAW devices contain metal electrode deposited periodically on their surface.When the wavelength of surface wave is exactly twice the period of the metal electrode,Bragg reflection occurs.Owing to the Bragg reflection of SAW,we can design and make all kinds of SAW devices such as resonators,bandpassfilters and metal strip reflectors,etc,with MEE propertities.Based on this background,the propagation behaviors of Bleustein-Gulyayev?BG?waves and Rayleigh waves near the Bragg resonance frequency in a transversely isotropic MEE substrate with a periodically metal electrode perturbed surface are investigated theoretically in this paper.The main contents are as follows:?1?Using the field analysis method and the Coupling-of-Mode?COM?theory,respectively,we study the propagation behavior of BG waves near the Bragg frequency in a transversely isotropic MEE substrate with a periodically inertial loads surface.The dispersion curves and frequency responses for?80%Ba Ti O₃/20%Co Fe₂O₄?substrate are calculated numerically,with considering the effects of two perturbed parameters,one is uniform inertial load and the other is periodically changing load,on dispersion curves.Results show that:the results obtained by the two methods are in good agreements.When the frequency of incident waves is at the center frequency of the band gap,BG waves decay the fastest.The width and the location of the band gap,respectively,mainly depends on the periodically changing load and the uniform inertial load,respectively.?2?With the variation principle?VP?and the perturbative theory?PT?,combined with the COM model,we study the dispersive characteristic of Rayleigh waves near the Bragg frequency in a transversely isotropic MEE substrate with a periodically perturbed metal electrode surface.The first-order reflection coefficient,velocity shift and dispersive curve for?Ba Ti O₃/Co Fe₂O₄?substrate with Al and Au electrodes,respectively,of Rayleigh waves are numerically calculated.Results show that:the results obtained by the VP and PT methods are in good agreements for Al electrode case.As compared to Al electrode case,the dispersive curve of Au electrode case appears in a lower frequency range with a wider gap.Au electrode case has a more obvious effects for Rayleigh wave propagation in MEE substrate near its Bragg resonance frequency.The work of this paper will provide the guides for the design and application of the related MEE SAW devices.