Reply To: simulating Surface acoustic wave resonator

[wrbulat]

Hi,

Be sure to apply periodic boundary conditions in your ANSYS model that are consistent with those applied in the COMSOL model (if any). Also be sure the direction of polarization of the piezo materials is consistent with that defined in the COMSOL model. In 3D piezo models, our piezo and anisotropic elastic matrices are usually defined in such a way that polarization is in the z direction. Assuming this to be the case, define a coordinate system with its z direction aligned with the desired direction of polarization direction in the piezo body in the physical device, and specify that coordinate system in the Coordinate System field in the piezo body details:

 

If you manually defined the piezo and anisotropic matrices yourself, you may have entered the data in the order consistent with the convention used by IEEE. The convention used in ANSYS differs from this as explained in the Help:

 

The electric charge on a free surface with no voltage constraints, no coupling on the VOLT DOF, and no enforced charge density should be zero - it is naturally occuring. I suppose you could use a command object to define, using the SF commmand, a zero charge density on a surface:

but that shouldn't change the calculated results from those you would get if you didn't do so.

 

I would suggest making a single part out of all the bodies in your model, and apply voltage boundary conditions on the piezo body surfaces that are interfaces with the electrode bodies. You should then be able to assign the electrodes to a structural physics region (they only add a little mass and structural stiffness to the system).

 

I hope this helps you,

 

Bill