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February 9, 2012 8:30pm UTC

Stretching+Inflation

Hi,

I have a 2D problem in which an arc of a circle undergoes two consecutive deformations (Please see the attached mph and PDF files). I use a two-step study which also happens to have two Physics in order to change some of the boundary conditions throughout the deformations. Also because the geometry is symmetric, I only simulate its upper half. The Steps try to deform the geometry as follows:

Step 1:
The right end is a symmetric boundary and the left end is stretched in circumferential direction to create a closed cylinder. Through this deformation, the central angle of the arc will change from 71.4 to 180 degrees.

Step 2:
After the solution is saved by “Store Solution”, the left end will change to Symmetry and the surface on the inner radius will go under a pressure to inflate the cylinder. I do this by a parametric study by setting an Extension in my “Step 2: Inflation” node.

I have run into a few problems:

1- Although I have used a “Store Solution” in my Solver after the Closing solution, inflation does not use the stored data and therefore does not start from the first deformation (i.e. closed cylinder); in other words it starts from the original unclosed arc. However, it correctly enforces symmetry condition for the left boundary before it solves for the inflation.

2- In the second step of the solution which is inflation, although the boundaries are symmetry, the solution never converges as if the problem is indetermined. This obviously does not occur if I wanted to simulate a full cylinder and not half of it. Adding at least one constraint such as fixing one node on the geometry makes the problem mathematically determined but the physics of the problem will be compromised. Is there any approach that can resolve this issue?

3- I have set the program so that it plots the results while solving it. I have experienced that sometimes I do not get one of those plots during the solution. I mean sometimes, the result of Step 1 is shown during solving, but not the results of Step 2, and sometimes the other way around. I was wondering if this is a bug or I am missing something.

Please see the attached mph and PDF files and let me know how I can fix these problems.

Thank you for reading my posting,
Jessica

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