Discussion Forum

Hi

In both versions you can define Corrdinate Systems, and then you apply the IEEE convention PZT material data base data (just enough different to the usual structural way that you get it often up-side down, check carefully) to this User coordinate system and not to the Global one.

For plotting you have advance cross section plots, and if you scan through the sub itzems (mostly hidden by default) of the plot tree you can redifine the default "x" axis with an expresson

Finally for both versions you can add cutom material to your own database that you link up to the default COMSOL one, check the doc

I agree threr is quite a lot to learn new, the best is to systematically try it out (or as me, do your best to reply to the Forum, and in this way discover and train the subtilities of V4 :)

Have fun Comsoling
Ivar

HI,

Thanks for you answer.

However, I tried to find information about the way to add or change a coordinate system (right click on Definitions in the Model Builder and then Coordinate system) but I still do not know what is what (for ex, what is t1,n and t0 in the boundary system and to what correspond the usual x,y and z axis ?) and to define the given variables for my problem.

And does it exist a tutorial or User's guide for the 4.0 version like for the 3.5 one? Because as soon as I want to analyze or realize something more difficult with my basic geometries and settings, I'm just not able to do it although there is no problem with the 3.5 version.

Have a nice week.

Nicolas

Hi

I have neither not a full view yet, but the default "Boundary system SYS1" is the boundary system defined on any surface = boundary of your system. The 1,2,3 are the three coordinates in that order for a right hand cartesian projection, usually x,y,z or t1,t2,n (in 3D) where n is the normal (outwards = up). t1 and t2 are the tangents of your 2D boundary. t1 is selected from the global cartesian + axis = 3 or generally =z (by default) or you define yourselve with an edge the direction you want to use to define t1. in 2D you have only t and n (as 1 and 2)

You can create any new coordinate system by right click on the "Model - Definition - Coordinate System". These user CS are handy to define particular PZT orientations. You have different ways to define them. Unfortunately COMSOL has not given us, yet, any simple way to visualise how a user CS is oriented grpahically, so I usually define a force or any particular vector I can visualise with an arrow after a "get initial conditions" just to check that my CS 1,2,3 (ur x1,y2,z3 direction are well as I expect them.

Another unfortunate situation is that we cannot use the CS for the postprocessing (yet) I hope it will come soon, as its very usefull, one do not always want to calculate the vectors by hand when the global x,y,z orientation is not the only one to report back for.

Hope this helps
Try it out on simple cases, and read through the doc, v4.0a has improved already from previous v4.0, more will certainly come
Ivar

Thanks Ivar for your complete answer.

To my opinion, it's like if the COMSOL engineers want to hide settings or make things more difficult although the 3.5 version was logical and clear. Strange...

I will try your tricks and see if it works :-)

Nice evening

Nicolas

Hi,

Just some additional information:

In 4.0a it is possible to plot all user-defined coordinate systems with dedicated Coordinate System Volume, Coordinate System Surface, and Coordinate System Line plots, which you find on the More Plots submenu in the plot groups' context menus. The visualization uses triplets of red, green, and blue arrows to illustrate the coordinate system directions.

Regarding 2D piezoelectric material orientation:
The functionality you see results from the improved coordinate system support in the version 4 of COMSOL Multiphysics. In 3.5a we supported 2D coordinate systems in 2D models. When a piezoelectric material is defined as in 3D, an additional setting was needed that prerotated the material. And the final material orientation resulted from two settings: the material orientation list and the defined coordinate system.

In version 4 everything works as in 3D, and everything related to material orientation is defined in one place: Coordinate Systems. Whenever you define a 2D coordinate system you also define the out-of-plane coordinate, which has the same effect as defining the material orientation in 3.5a.

We consider adding a coordinate system automatically for 2D piezoelecric models. A coordinate system that corresponds to the 3.5a default is the following:
Base Vector System with
Out-of-plane index = 2
Base vectors:
x1: 1 0
x3: 0 1

Best regards,

Magnus Ringh, COMSOL

Hei og takk Magnus

You have so many options that we just do not find them all, now in V4 ;)
I have been waiting for the plot with custom coordiante system for a long time, now it is/have been here and I havent even found it.

Hope you get a "show/visualise" coordinate system too (have to check if it is there nowin 4.0a) to help us check the orientation when defining custom coordinate systems. Then life will be perfect :)

And what if we could select a new Defiinition View w.r.t. a custom CS (new suggestion ;)

Having fun Comsoling
Ivar

Thank you all for your further explanations.

Best regards

Nico

Hi all,

I'm trying to do the analysis of stresses on different orientation of grains. I wonder if comsol able to do that. If yes, how can I set different orientation on grain that are beside each other?
Thanks