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Abaqus explicit problem / Step time stop but increment increase

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Posts: 23
Topic starter
(@nctfat)
Eminent Member
Joined: 14 years ago

Dear

I have weird problem. I run one Abaqus explicit job which must model a bulk deformation by Johnson Cook constitutive model from Abaqus material library. NO VUMAT or other subroutines.

When I run the job due to small mesh in one corner it takes a lot of to time to run the model, The problem start nice when step time reach 0.065s in time step the increment increase but the time step is remained constant on 0.065. I leave the program for 2 to 3 hours but increment increase and the time step stop on 0.065.

By removing ALE adaptive the time step reach 0.0736 and then increment is increased but the step time is constant on 0.0736.

Due to no error I cant recognize the problem:(

I need your help to make some suggestion or solution,)

best regards

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

I dont quite follow your description. What time increment size (dt) does the simulation use?
Are the elements distorted?

-Jorgen

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Posts: 23
Topic starter
(@nctfat)
Eminent Member
Joined: 14 years ago

Yes the elements distorted . This is the modeling of deformation of copper under constant strain rate.
About the time increment I am not sure but it is near 3.80E-09

These values are from STA file which the third column shows what I mean. The first column which shows increment increase but the second third one stop on constant step and total time

24251447 7.362E-02 7.362E-02 06:57:58 3.725E-09 1614 1.211E-11 -1.270E+00
24371894 7.362E-02 7.362E-02 06:59:58 3.725E-09 1614 1.040E-11 -1.271E+00
24492066 7.362E-02 7.362E-02 07:01:58 3.725E-09 1614 1.188E-11 -1.271E+00
24611995 7.362E-02 7.362E-02 07:03:58 3.725E-09 1614 9.318E-12 -1.271E+00
24731885 7.362E-02 7.362E-02 07:05:58 3.725E-09 1614 1.067E-11 -1.271E+00
24852285 7.362E-02 7.362E-02 07:07:58 3.725E-09 1614 9.968E-12 -1.271E+00
24972239 7.362E-02 7.362E-02 07:09:58 3.725E-09 1614 1.041E-11 -1.271E+00
25092317 7.362E-02 7.362E-02 07:11:58 3.725E-09 1614 1.506E-11 -1.271E+00
25212260 7.362E-02 7.362E-02 07:13:58 3.725E-09 1614 1.172E-11 -1.271E+00
25332690 7.362E-02 7.362E-02 07:15:58 3.725E-09 1614 1.167E-11 -1.271E+00

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Posts: 93
(@kiranckst)
Trusted Member
Joined: 14 years ago

Thats a huge number of solution increments. Your time-increment is too small because of element distortion. It seems the total time isnt increasing when it actually is beacuse the time increment is so small. Try and limit the distortion or look at mass scaling to increase the time increment size.

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Posts: 23
Topic starter
(@nctfat)
Eminent Member
Joined: 14 years ago

Thanks
your suggestion about mass scaling was great .

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