initial stress problem

[epd20]

Hi all,
I have to start again a new thread to ask you if you could help me solve this problem.

--------------------------------------------
MAT 2 d=100 nm PLANE82
--------------------------------------------

MAT 1 d=1 micron PLANE82

--------------------------------------------

I have a bimorph beam, as depicted above, both ends fixed in x-y direction (it's a 2D model with plane82 elements), I apply a high initial constant stress (6 GPa)to material no 2 and the beam, as it should be, bends towards the side of material no 2. Now, what it's not normal it's that the displacement is really smaller than the expected one (around .1e-18 m for a .1mm long beam).
I am actually missing something.

Is it correct to use
istress,6e9,0,0,0,0,0,2
to apply a x-direction constant stress to material 2?
(I realise this sounds silly but I'm asking myself what's wrong with my model and I keep examining the few details..)

Is there any keyopt to declare to plane82 element type to observe a large displacement? Actually, I would expect a few microns bending for such a long beam.

Any suggestion would be really welcome
Thanks for your help
Emile

http://www.master-nanotech.com/

http://www.polito.it/