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Nonlinear modeling of pressure vessel

Nonlinear modeling of pressure vessel

Nonlinear modeling of pressure vessel

(OP)

I use COSMOSWORKS to model a pressure vessel (like cylindrical shape) made of fabric having a large force applied on the top partial flat surface and internal pressure inside. The thickness is very small, and diameter-thickness ratio is around 4*10^4.

I first use linear static analysis and it showed large displacement. Then, I checked the option of large displacement and run. It showed error: can only complete 25% load step, fail...

Now I try nonlinear analysis. I use different options of fixed time increment and it still showed the error that the load step is too big. I use shell mesh and the mesh is very coarse.

I can only try to decrease the time step now and every time it runs for a long time and show the error again. Is there any way that I can solve this problem?   

Thanks for any input!

  

RE: Nonlinear modeling of pressure vessel

Sounds like maybe excessive deflection? Have you done any hand calcs to see if you are in the right ballpark with regard to loading and geometry of your part? I would double check your constraints and then see if I could get it to run with a much smaller load.

RE: Nonlinear modeling of pressure vessel

(OP)
Thanks for the reply.

I can not use analytical formulas to calculate because there is a large force applied on the top. I changed the thickness and found that even linear static analysis is working. That's the problem of excessive deflection, which is also too big for nonlinear analysis.  

RE: Nonlinear modeling of pressure vessel

It may have buckled in some way and so large deflection goes off to infinity.

corus

RE: Nonlinear modeling of pressure vessel

You are of course using a shell model for this.

The heads of cylindrical vessels frequently will buckle in compression when there is pressure inside. Do a run with a small load and look for circumferential compressive stresses. If this is happening you have to export your model and run it in geostar using a shell element with a wrinkling option.

KTOP

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