defining a node and element locations while meshing a volume

Hi,

     I am trying to model a piezo disc bonded to a steel plate for lamb wave simulation. I am currently modeling the piezos as rectangular with nodes coincident with the plate nodes and just coupling them. I would like to do that with a circular geometry for the piezos, but for that I need to define nodes in the disc that coincide with the plate nodes. How can I do that? Can I define my own node locations in a volume for meshing? Thanks in advance for your help.

Muhammad Haroon