Plot Result In A Cylindrical Coordinate in COMSOL 1

[FEAppp]

Hello, I want to visualize the stress tensor in the cylindrical coordinate. Currently, I have the output from a 3D solid mechanical model. The expression I choose is solid.sx, solid.sy, solid.sz and etc. However, these are all plotted in the global coordinate. I want to visualize the result in the cylindrical coordinate.

I also tried to define a cylindrical system and selected it in the linear elastic material (solid mechanics). And then visualize the result in solid.slxx, solid.slyy and etc. But the thing is: the stiffness matrix I input for anisotropic material is based on the global coordinate. So if I selected the cylindrical system in the linear elastic material (solid mechanics), the calculated result give me a wrong output.

SO I want to know whether there are some other ways to visualize the stress in the cylindrical coordinate.

Thanks.

 

[FEA way]

Try this:
- solve the simulation without local coordinate system
- define cylindrical CSYS and specify it in the Linear Elastic Material node
- instead of solving use "Update Solution"

 

[FEAppp]

Hello FEA way,

It is also not correct. When I update solution, the original solid.sz solution changes. However, this stress tensor shouldn't change since it's correspond to the global coordinate stress tensor. That being said, I still think that the comsol treated my stiffness matrix I input is based on the cylindrical csys after I update solution.
I defined the csys. Attached.
Do you have any ideas?

Thanks,
Wenjing

 

[FEA way]

This should work:
- set Linear Elastic Material --> Coordinate system: Global coordinate system
- run the analysis
- in the Expression field of the stress plot type: solid.sz*sys2.T33

Second term in this equation is coordinate transformation to local coordinate system named sys2 for the 3rd component. You can find it under Model --> Component 1 --> Definitions --> Cylindrical System 2 --> Coordinate transform to system (sys2).

 

[FEAppp]

Thanks FEA way, it works for z component!
But what about I want to see the radial stress, sigma_rr?
I tried to use solid.sx*sys2.T11
But the result I got is incorrect.
Do you have any ideas where I did wrong?
Thanks a lot.

 

[FEA way]

It seems that for radial and tangential components this is more tricky. These formulas should work:

- for radial component:

(x^2*solid.sx+2*x*y*solid.sxy+y^2*solid.sy)/(x^2+y^2)

- for tangential component:

(y^2*solid.sx-2*x*y*solid.sxy+x^2*solid.sy)/(x^2+y^2)

Axial component will be simply solid.sz

 

[FEAppp]

Hello FEA way,

Thanks a lot! It works~

Wenjing