Problems with cooling simulation

[Odyone]

Hello,

the model consists of a aluminium/steel matrix. A cylinder is placed in the center of the geometry. The cylinder has been generated via a Boolean operation. The Matrix is cooled down from 400°C to 20°C by a nonlinear static analysis(i want to avoid a transient or coupled analysis).
The results of the simulation are erroneous: the principal stresses are all the same (only tensile) and as a result of this the vom Mises equvalent stress is zero.
So I implemented a test simulation without the cylinder.
The results of the test simulation are far more reliable:There are tensile and compressive stresses and the overall distribution of the stresses is as expected.
The material law is identical for both simulations(see attachment).
At this time i don´t have a clue why this differences are occuring.

Thanks

 

[Transient1]

Is your model properly constrained? Are both cases you have tried free thermal expansion?

I think your geometry is two concentric cylinders, is the mesh continous between the two or are you using contact elements?

 

[Odyone]

My model consists of blockvolume with the cylinder volume at its center. The mesh is continous, i designed the whole structure by using the VSBA command(dragged areas through the block first).
I constrained the modell at the lines parallel to the z-axis, all DOF =0.This has to been seen as a compromise to the mechanical loading which will follow the thermal simulation once it is working.In reality the structure is cooling down to ambient temperature (20°) at the air. As far as i know there is no way to alter the constraints in a simulation without deleting the former results.
As to your remark, i also think the problem may be the modell contraints, but i in this specific case i have to regard the following mechanical simulation, where the structure has to be fixed properly to copy the setup in the real machining process.