How to do a Restart Analysis with linear perturbation step in Abaqus?

[kushwah_dk]

Hello Everyone, I am trying to do a Restart Analysis with linear perturbation step in Abaqus for the plasticity problem (or to calculate tangent modulus for Elasto-plastic material). Can you tell me how to store calculated values for each iteration during restart analysis?

 

[FEA way]

Why do you want to use a linear perturbation step (especially since plasticity is involved) and what kind of it ? Most of them are not supported for restart.

 

[kushwah_dk]

Because I want to calculate Macroscopic tangent modulus for Nonlinear materials using Perturbation Technique which is described in the paper "Comparative study of three techniques for the computation
of the macroscopic tangent moduli by periodic homogenization scheme".
Please check the attached document where the summary of the procedure is given.
And my doubt is regarding step-2 that how to implement restart analysis with perturbation step?

 

[FEA way]

This way it’s possible. You can’t save the restart data in static linear perturbation steps (so you can’t restart from them) but you can read restart data in those steps (so you can restart to them).

 

[kushwah_dk]

It means if step-1 is general static step with increment loading (suppose 10 increments are there) then in step-2 for each increment (10 times) we will have to read restart data?
If yes, so is there any way by which we can read all data simultaneously?

 

[FEA way]

You can restart from only one increment in each analysis so you will need multiple restart analyses with perturbation steps if you want to restart from different increments. That’s what they describe in the article (they use 9 restart analyses).

 

[kushwah_dk]

Thank you for your reply.
My doubt is related to the tangent modulus (9x9 matrix). Here in step-2, 9 restart files are used for calculating 9 columns.
But in step-1 if there is 10 increments then should be need to generate total 90 restart files (9 for each iteration)?
Because incremental load is used in the plasticity problem, is it?

 

[FEA way]

I’m not familiar with the technique described in this article but, based on the input file included as Appendix B1, it seems that you need 9 restart analyses for each increment of an original nonlinear analysis. That’s why they mention the usage of Python scripts to automate the process.

 

[kushwah_dk]

Ok, Thank you so much.

 

[kushwah_dk]

Hello Sir,
I have a doubt regarding the restart procedure. I have created step-1 where displacement is specified as 0.1 at a particular node (see the attached fig). Now I want to use restart analysis after completion of step-1 and in step-2 I have created another displacement BCs 0.00001(at the same node)using linear perturbation step. Here the stresses should be increase after the completion of the job but in my case step-2 does not have any effect of step-1(because the same values I am getting in step-2 with and without using step-1).
How to resolve this issue please help.

 

[kushwah_dk]

Hello Sir,
"This way it’s possible. You can’t save the restart data in static linear perturbation steps (so you can’t restart from them) but you can read restart data in those steps (so you can restart to them)" this you mentioned in your reply dated 21/06/23. Could you please explain just for the one increment that how we can calculated perturbed stresses?
I tried many times but I am getting same results for each iteration for perturbation step. I am stuck what to do?