The double dot indicates an inner product over two indices of the tensors (A list of symbols is provided in the nomenclature at the end of this paper). This relatively general form is difficult to work with, but by making two assumptions, the equations may be simplified. For the entire volume of an elastic body, excluding the exterior surfaces and interior flaws, the stress tensor is symmetric, so an initial assumpution is that the stress tensor is symmetric throughout the area of interest. Further, for this application (and for most others), the electrical field travels through the material at much higher speeds than the strain field -- fast enough to assume that from the perspective of the mechanical motion of the plate, the electrical fields in the piezoelectric laminas change instantaneously. In other words, the motion of the piezoelectric laminates is quasistatic. By contracting the tensor notation as in Auld [21] and applying the symmetric stress tensor assumptions, equation simplifies to