Preload of a structure for thermal expansion 1

[MartaMed]

Hi everyone! I have a problem with a FEM analysis, and as I am very new in the field of Patran/Nastran I am a Little bit lost.
The objective is to study the stresses that suffers a seal ring installed inside a cylinder due to thermal expansion. In order to do that, I have to first apply the radial load that the outer cylinder transmits to the seal ring, so the ring has a certain compression. Then, I have to increase the temperature so as to study the thermal expansion of the ring. The problem is that for doing the first step, there is no constraint in the outer contour of the seal ring, and for applying the temperature I have to restrict the radial movement for the outer contour of the seal ring.

I do not know if it is possible to 'save' the stresses and displacement of the first case so I can introduce it on the second problem without the load and with the radial movement restriction. Maybe is there a simpler way of doing this analysis, but my knowledge is limited.

Thank you very much!

 

[gravityandinertia]

Can you run this as an axisymmetric model? That would remove you constraint problem. A picture could help describe the problem better.

 

[aerostress82]

Good one. You should find a way of saving the firts loading's stresses. If you are using Nastran version 2013 or later, your answer might be in SOL 400 examples. But if you can figure out an easy way of saving those stresses from initial displacements for both inner and outer cylinders, that should also help. Never done this, but I remember seeing a Sol700 birdstrike analysis example with pre-stresses on the engine blade. It looks more like a SOL400 analysis with STEP cards in it. You will have 2 Steps as subcases. I didn't do this exactly but if I wrote Nastran, I would add a CARD to my code for step 2 where all the stresses from Step 1 would be accounted for. If someone could confirm this, or if you coukd find it from Nastran examples and reference books, I'm sure you are very close to solving this problem..

Spaceship!!
Aerospace Engineer, M.Sc. / Aircraft Stress Engineer

 

[MartaMed]

Thank you very much for your answers. aerostress82 I tried to do a SOL 400 with two steps as you recommended, but I do not know how to take as an input the stresses from the first step. If someone know how to introduce the stresses from step 1 for the step 2 it would help