ANALYSIS OF SURFACE EXCITATION OF ELASTIC WAVE FIELD IN A HALF SPACE OF PIEZOELECTRIC CRYSTAL（I）——GENERAL FORMULAE OF SURFACE EXCITATION OF ELASTIC WAVE FIELD

This paper developes the general theory of the surface excitation of elastic wave field in a half space of piezoelectris crystal for both free and metallized surface. It is shown that tre general elastic wave field U is equal to the convolution of the generalized Green's functions G and the generalized forces T,U=G⊗T,where symbol ⊗ expresses dot-product-convolution.
The generalized Green's functions are independent of excitation conditions and only dependent on material paramaters and orientation.
For the piezoelectric crystal, not only a mechanical source distribution at the surface, but an electrical source distribution also can excite the elastic wave fields. A complete expression of the generalized forces representing respectively mechanical and electrical source distribution is geven. For the free surface especially, the surface electrical sources can be composed of the discontinuity of normal electric displacement at the surface, and of the dis-continuity of the tangential electric field as well.