Abaqus shell modelling convergence issues

Modeling & Simulation
1

Dear community,

I have encountered an issue when modeling a cylindrical shell with S4R elements in Abaqus.

The model is shown below (the platform does not allow me to attach the .inp).

image
image624×305 14.8 KB

Model description:

  • Cylindrical shell (L = 52.501E-03 mm, D = 9.648E-03 mm, th = 0.001 mm) with a perfectly structured mesh quad mesh with elm size of 180.E-06 mm.

  • Compressible isotropic hyperelastic Yeoh material.
    *Hyperelastic, yeoh
    0.000615, 0.002488, -0.001183, 162., 0., 0.

  • Static General step with NLGEOM=ON.

  • Axial displacement-controlled pure tension.

The response is expected to be purely membrane, with no bending.

The prescribed displacement 0.0315 mm is applied using an amplitude function:
1. From 0 s to 200 s, the displacement increases rapidly.
2. From 200 s to 1000 s, the displacement is held constant.
*Amplitude, name=Amp_paper, time=TOTAL TIME
1., 0.5, 10., 0.658333333, 22., 0.725, 44., 0.791666667
74., 0.866666667, 106., 0.933333333, 148., 0.975, 200., 1.
1000., 1.

Unexpectedly, the analysis diverges at approximately 720 s.

There is no additional loading applied after 200 s, the displacement increment is 0.
The model remains stable with perfectly uniform stress distribution until around 586 s.
Then, a localized stress concentration begins to develop spontaneously; eventually the solution diverges at about 720 s.

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image624×213 15.6 KB
t = 406 s

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image624×217 15.7 KB
t = 665 s

Has anyone encountered similar behavior with S4R shell elements or hyperelastic materials?
Any suggestions on possible causes would be greatly appreciated.

Thank you.

2

@kmao24 can you help?

3

j-tiny-tube-pull.zip (11.6 KB)

Hi, Denism, Based on your description, the model should not have a convergence issue, unless something more in your model. I created a model in accordance with your descritions, and it converges quickly. Please compare my model with yours to see what kind of differences are.

Regards, kmao24

4

Hi, Denism, One more note: my previous response was based on relatively coarse mesh. I also tested another case using your mesh size of 180e-6 mm, and the model also converges quickly.

Regards, kmao24

5

Hello Kmao24,

Thank you very much for such a prompt response.

Yes, with automatic incrementation the model converges without any issues. The problem arises when you force it to make smaller increment. Unfortunately, I cannot attach my .inp because I am a new user.

If you could kindly share your .inp with fine mesh, I will be able to modify the Step parameters to show the issue and post back the modified lines.

Best regards,

Denism