A New Type of Energy Trapping Caused by Contributions from the Complex Branches of Dispersion Curves

I- a - U. Abstract The energy trapping of width-extensional vibra- tions in a thin piezoelectric ceramic strip is studied, and it is shown that a new-type of energy trapping by contributions from complex branches oc- curs in the vicinity of the stationary points on dispersion curves. The trapped-energy modes have some interesting c haracteristics, such as: 1) The resonant frequency curves as a function of the electrode-length/strip-width ratio exhibit notice- able undulations. 2) The decay of displacements with distance from the electrode edge is accompanied by sinusoidal oscillations. 3) The ratio of capaci- tances becomes a minimum at an electrode length where the resonant frequency curve begins to undu- late, and increases abruptly as the electrode length grows larger. The existence of this type of energy trapping is also verified experimentally for thickness-extens ional vibrations in a piezoelectric ceramic plate.