Influence of electrical boundary conditions on Lamb wave propagation in piezoelectric plates

When a Lamb wave propagates in a piezoelectric plate, it may be governed by three kinds of electrical boundary conditions on two surfaces of the plate. They are: (1) both surfaces are electrically open (oo); (2) both are electrically shorted (ss); (3) one is open and the other is shorted (os). Under these conditions we calculated the dispersion curves of Lamb wave in Y-Z and 128° Y-X lithium niobate plates. The obvious influence of the electrical boundary conditions on Lamb wave propagation is found from the calculations. Especially, it is found that electromechanical coupling coefficient K² of Lamb wave can be evaluated simply from the velocity difference of Lamb wave under the conditions oo and ss