Obtaining mass and stiffness matrices in cylindrical coordinates 1

[alain10025]

Hello,

I am using Ansys to study a cyclic symmetric structure. But I just use it to obtain the mass and stiffness matrices of an elementary sector.

In order to make the analyze of the matrices easier, I need to obtain them in global cylindrical coordinates. It is why I have a problem.

After importing my FE model in Ansys (the elementary sector), I use the commands :

- CSYS,1 to work in cylindrical coordinates
- EMATWRITE, YES
- WRFULL to get the files containing the mass and stiffness matrices.

However, this seems unefficient because I get the matrices in global cartesian coordinates.

Would anyone know which command is required beside of "CSYS,1" to be sure to obtain the matrices in global cylindrical coordinates ?

Thank you.

Alain

 

[meshparts]

Hello,

I don't know if what you want is even possible in Ansys. It it is possible, then csys,1 would not have any effect anyway.

RSYS,1 on the other hand could have a chance to do, what you would like to do.

Regards,
Alex

 

[cbrn]

Hi,
sometimes it's the "DSYS" command which governs the listings of coordinates. If the suggestion of the "RSYS" doesn't work, I'd have a try with DSYS.

 

[alain10025]

Hello,

I tried RSYS,1 and DSYS,1 none of them seems to give waht I am looking for ... I know this is possible to do with Ansys because I did it already with another structure that was imported from Nastran.

In order to knoe where could the problem be from I edited the .db files of the previous structure and the one i am studying now, the only differences (beside of the structures data) are in :

Record 2 -> 5th position ("1" instead of "0")
Record 7 -> 61st position ("6" instead of "-1")

I tried to look in the Ansys Interface Guide but I couldn't find the meaning of these records in an input "db" file ...

Thank you for your help.

Alain

 

[cbrn]

Ah, perhaps I've got an idea: rotate the nodal and element coordinate systems to a cylindrical one. Note that this may not be done with the default CSYS,1 so you have to replicate to a local user-defined one for example CSYS,11.
To rotate the nodes:
CSYS,11
NROTAT,all
To change element's coordinate system:
EMODIF,...

Regards

 

[alain10025]

Thanks a lot cbrn, it seems that

CSYS, 1

and then

NROTAT, ALL

can make what I was looking for !

Alain

 

[cbrn]

Hi,
glad it works!...

Regards