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[Solved] UMAT-convergence problem

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Posts: 2
Topic starter
(@vasavdubey)
New Member
Joined: 7 years ago

Hi,

Im simulating the behavior of anisotropic material using a UMAT subroutine. The UMAT works fine when using single element. However, when I use multiple elements (C3D8R), I get convergence problems.

The problem is as follows:
The simulation stops suddenly with error Too many attempts...... The point where the simulation stops depend on the elements size. When I increase the element size (coarser mesh) I get better convergence, but for finer meshes, the simulation isnt completed.

Ive tried to increase the hourglass stiffness, and I found that for higher values, the simulation is completed, but the resulting forces are higher !

Is this problem coming out from the definition of the DDSDDE matrix inside the UMAT, or its a result of using reduced elements (C3D8R)?

Thank you in advance.

Best Regards.

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Posts: 16
(@Baldwin)
Active Member
Joined: 9 years ago

Hi everybody.
Wishing you all a ggod day.
WHile using UMAT, I am getting following errors.
WindowsError: [Error 2] The system cannot find the file specified UMAT
This is the 1st and last line of the error and nothing else.
(Know that I linked my Fortran and Abaqus in Target)
Kindly help.
Thanks in advance.
PMG

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

It is difficult to specify what is causing your convergence problem without having more info. If you switch to another built-in material model do you still have problems? If not, the issue is likely caused by your Jacobian (DDSDDE).

-Jorgen

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Posts: 3998
(@jorgen)
Member
Joined: 5 years ago

It is difficult to specify what is causing your convergence problem without having more info. If you switch to another built-in material model do you still have problems? If not, the issue is likely caused by your Jacobian (DDSDDE).

-Jorgen

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