Discussion Forum

Hi

if I read you right, your crystal X,Y,Z orientation is the one you have plotted, and your COMSOL (x-y) SAW plane is at the Euler (Z-X'-Z'' convention) angle, or at (0,132.75,0)°.
Then you need to convert back a user coordinate system, that starts in COSMOL's x-y plane by a rotation of -132.75° along Rx (as the two other roations are "0") to reorient your coordinate system from the COMSOL x-y plane ito the crystal X,Y,Z plane

Or have I missed something ?

Then in the crystal reference you use the user sys2 (probably) reference and not the default cartesian coordinate system

In v4.2 you have in the more options of the plot node the possibility to add coordiante references on points or edges or planes

--
Good luck
Ivar

Hi Ivar, thanks for responsing, but this rotation needs me not for plot,
may be i wrote wrong

So,

In this exersice I have ST-cut quartz like surface material and I need to model SAW resonator on this
I need to determine crystal coordinate system, then to use it in "piezoelectric material" node

I tried to use this many times in different variations like basic vector sys, rotated, etc
Because of using 2D mode, I cant simply put Eulers angles to rotated sys: in 2D rotated sys you need choose "out-plane' axis and rotate crystal plate about this. But in this case with my cut - propagation of SAW go out of screen (check image in my past message) - it impossible

Like I think, I have only one way:
1. Use mapped coordinate system
But I dont know how to put axis vectors in this sys. I tried to put anything to the expression field, but have no working: velocity of SAW is changing in different propagations, and all results wrong.

My question: How to determine Mapped system coordinates?

Many thanks for fast answer
R

Hi

I believe I start to see your issue ;)
If I do a simple block model in 3D I can orient a Rotated system in 3D (with the Euler angles (0,-42.75°,0) and get your image vector orientation, with the electrodes in the X-Y plane at two different Z height locations. Then I can get a 3D X-Z plane (corresponding to your 2D x-y SAW plane) and see the PZT deformations.
this gives you strain matrices elements, in the local coordinate system, of the type
pzd.el11
(sys2.T11*uX+0.5*sys2.T12*(uY+vX)+0.5*sys2.T13*(uZ+wX))*sys2.T11+(0.5*sys2.T11*(uY+vX)+sys2.T12*vY+0.5*sys2.T13*(vZ+wY))*sys2.T12+(0.5*sys2.T11*(uZ+wX)+0.5*sys2.T12*(vZ+wY)+sys2.T13*wZ)*sys2.T13

But now to remap this into 2D with a 3D Rx rotation for a material plane coordinate system, I cannot find the COMSOL commands, and referring to "z" or "Z" in 2D brings an error message Z unknown
And the then the local strain matrices are
pzd.el11
(sys2.T11*uX+0.5*sys2.T12*(uY+vX))*sys2.T11+(0.5*sys2.T11*(uY+vX)+sys2.T12*vY)*sys2.T12

missing all coupled "Z" terms

So probably you need to write out manually the coordinate mapping in 3D and use that in 2D. But you can be inspired by the 3D model.

I find it worth to send off a mail to support to have them explain to you how they considered this, it seems a bit strange that you cannot define a full arbitrary 3D coordinate mapping for PZT materials in a 2D model

--
Good luck
Ivar

Many thanks for helping, Ivar

Just havent understand how to do this:

So probably you need to write out manually the coordinate mapping in 3D and use that in 2D. But you can be inspired by the 3D model.

Please, may you explain how to do this stepp-by step? Where i can find coordinate mapping, how is it looks?

I get same picture, checked axes and now trying to work in 3D... have no much time

Big big big thanks you

Hi, Roman.

Maybe you should try with matrix transformations. www.comsol.com/community/forums/general/thread/15815/ . I used that for a SAW pressure sensor on Lithium Niobate 128° YX 2D simulation.

But right now I am modeling the deformation in the substrate by the applied pressure. How did you do that?.

Thanks for your reply.

Hi, I am a student from China, and I'm trying to model APM using ST cut quartz (Euler Angles are 0, 132.75, 0) in 3D. How can I define the material coordinate system? Is it (0. -132.75, 0)? I am confused. Looking forward to your reply. Many thanks.

Hi, Roman.

Maybe you should try with matrix transformations. www.comsol.com/community/forums/general/thread/15815/ . I used that for a SAW pressure sensor on Lithium Niobate 128° YX 2D simulation.

But right now I am modeling the deformation in the substrate by the applied pressure. How did you do that?.

Thanks for your reply.

Hi, I am a student from China, and I'm trying to model APM using ST cut quartz (Euler Angles are 0, 132.75, 0) in 3D. How can I define the material coordinate system? Euler Angles should be (0. -132.75, 0)? I am confused. How to define the crystal reference.
And I've read the pdf file of thickness_shear_quartz_oscillator contained in the model library, the material coordinate system for AT cut quartz has a rotation of - 54.75 along x. To my understanding Euler Angles for AT cut quartz are 0, 125.25, 0, the material coordinate system should have a rotation of - 125.25 along x.

Looking forward to your reply. Many thanks.

Hi

if I read you right, your crystal X,Y,Z orientation is the one you have plotted, and your COMSOL (x-y) SAW plane is at the Euler (Z-X'-Z'' convention) angle, or at (0,132.75,0)°.
Then you need to convert back a user coordinate system, that starts in COSMOL's x-y plane by a rotation of -132.75° along Rx (as the two other roations are "0") to reorient your coordinate system from the COMSOL x-y plane ito the crystal X,Y,Z plane

Or have I missed something ?

Then in the crystal reference you use the user sys2 (probably) reference and not the default cartesian coordinate system

In v4.2 you have in the more options of the plot node the possibility to add coordiante references on points or edges or planes

--
Good luck
Ivar

Hi

I'm not sure for the angles, I always have to carefully check myself ;) there are a few threads on that if you search, as well as some examples was it in the model library or the model gallery ? or even the Knowledge base, cannot fully remember

But a trick I always uses: plot the final direction of your coordinate system to check the orientation: for that you need to solve for the initial conditions, to populate the data set and result tabs, then add a plot - more - coordinate and select your user Defined coordinate system

Ivar

Thanks for answering. But I still couldnt understand.
As I've said, AT cut quartz's euler angles are (0, 125.25, 0). I tried different ways to model the quartz resonator.
First, the geometry and material sys are all in global, but I calulate the material constants using 125.25 and define them myself and get the right results.
Secondly, I use both 125.25 and -125.25 to rotate the geometry. It turns out -125.25 is right.
Thirdly, I I use both 125.25 and -125.25 for material sys. It turns out 125.25 is right.
The results are exactly the opposite from what I predicted.
Could you explain this for me?
Many thanks.

Hi,
I have the same problem as Roman. I use the YX 36° LiTaO3.
The thickness of the substrate is along y-direction, the wave direction is along x-direction and the poling direction is rotated by 36° about the x-direction. In 3D, I defined a rotated coordinate system with Euler angles (0, -36°,0), then I use it in piezoelectric material node.
In 2D, if I apply a rotated coordinate system, I need to define an 'out-plane axis' to rotate the crystal plate about it. In the case of YX 36° LiTaO3, the propagation axis will be out of screen.
Please can anybody show me how to define the orientation of my substrate in 2D?