axisymmetric orthotropic shell 1

[addmenot]

Hi,
i have model an axisymmetirc fw shell, in patran and using Nastran as a solver, i used the ctriax6 element.The problem is how to define the material properties. I know the angle which the fiber made with the meridian of the shell, but the material property form required E11,E22,E33,NU12,NU23,NU31 and G13. I know the Ef, Et, Vft and Gft.

Q1-Do i need to calculate the E11,E22,E33,NU12,NU23,N31 and G31 for each element seperately, based on the angle which it make with the meridian. or E11=Ef E22=Et etc.

Q2-if yes, than what is the THE value present in CTRIAX6 entry shows?

Q3-Does any body has a sample code for this type of shell.

Amir

 

[pjhype]

If you are only dealing with a single ply with a constant fiber orientation then you can set E11=Ef, E22=Et, E33=Et, etc. Otherwise, you will need to calculate the material stiffness matrix using classical lamination theory. Patran should have a preprocessor to automate this for you.

Next, you will need to orient the material axis with the element axis. In NASTRAN, the element axis is defined by the order in which the grid points are specified on each of the CTRIA cards. The element orientation is therefore an intrinsic property of each element, and must be defined when the elements are generated.

I am not sure of the syntax in the current version of Patran, but in FEMAP, when you generate your elements, you can open up a window where you specify the "Element Material Orientation". Here, you can align the element axes with a user-specified vector, an angle, or a global coordinate axis. Alternately, you can generate all of your elements without specifying the orientation, then go back in and update (edit and re-build) all elements to define the orientation vectors. If you use either of these commands, you will not need to specify the orientation of each element w.r.t. the material axes.

pj