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Hysteresis in ABAQUS(rubber indentation)

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Posts: 3
 lysg
Topic starter
(@lysg)
New Member
Joined: 16 years ago

Dear Dr. Bergstrom

Im trying to rubber indentation. Rubber is highly sensitive to the strain rate.

Regarding analysis, I tried with HYSTERESIS option ABAQUS. I am using

CAX4H elements and Yeoh-model with ABAQUS v6.5.

*MATERIAL, NAME=MAT1

*HYPERELASTIC, YEOH

0.8,-0.05,0.005,0,0,0

*HYSTERESIS

1.6, 0.556, 4., -1.0

*STATIC

1.0e-5, 1., 1.0E-10, .02

My big problem is now that the calculation doesnt converge. I have tried to do the calcuation in ABAQUS/standard without *HYSTERESIS and that works fine, but when I include that card the problem gets really hard to solve for ABAQUS. Furthermore, rubber tensile test works fine, however indentation gets error with *HYSTERESIS.

Do you have any ideas?

Also, different *HYSTERESIS parameters show different error msg. The error msg is shown at the end of this thread.

How I get the parameters of HYSTERESIS? Does it need experimental data? Is it a material property?

Your help will be truly appreciated.

Sincerely yours,

Kyumin

*HYSTERESIS

1.6, 7., 6., 0.

***ERROR: TOO MANY ATTEMPTS MADE FOR THIS INCREMENT

*HYSTERESIS

1.6, 0.556, 4., -1.0

***ERROR: TOO MANY INCREMENTS NEEDED TO COMPLETE THE STEP

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

The *Hysteresis model should work just fine.
If you post the inp-file I will take a look at what is going on.

Thanks,
Jorgen

12 Replies
Posts: 3
 lysg
Topic starter
(@lysg)
New Member
Joined: 16 years ago

thanks a lot Jorgen

I post the inp-file.

I am grateful to any help from you.

kyumin

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

The Hysteresis parameters need to be determined from experimental data. Typically the neeed experimental data is uniaxial loading followed by unloading at a few different strain rates.

I tried your input file and unfortunately I also had problems making it work. I made a few minor changes (see attached file) in an effort to determine what caused the problem. These changes did not make it work 🙁

Instead I switched to my own UMAT implementation of the *Hysteresis Model (what I call the Bergstrom-Boyce (BB) model). It turns out that my UMAT implementation works much better in this case. The simulation (see attached file) finished without any problem.

I encourage you to explore what caused the built-in *Hysteresis model to fail. The poor performance is suprising to me. In my own work I always use my own implementation of the model (since it has more features than the Abaqus version) so I am not sure if the built-in model is always this poor.

- Jorgen

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Posts: 3
 lysg
Topic starter
(@lysg)
New Member
Joined: 16 years ago

Thank you for your reply.

I am thinking of buying UMAT. Fisrt of all I request some favors of you. I hope to check whether my inp-file(see attached file) works fine or poor.

I know already that BB-model needs 25 user material constants. I wonder what the each constant means.

Would you please help me?

Your help will be sincerely appreciated.

Kyumin

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

Kyumin, your input file works fine. I have attached an image showing the final distribution of Mises stress.

The first 16 parameters are global parameters that specify the behavior of the UMAT. The remaining parameters specify the behavior of the rubber.

-Jorgen

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Posts: 3
(@gabriele77)
New Member
Joined: 14 years ago

Rubber Bushing Loading

I have a somewhat similar issue with they hyperelastic material model. Im trying to translate a pressure to a rubber bushing but the solution wont converge and it states that the there is excessive distortion at multiple integration points. Which is kinda expected because im loading a rubber bushing. of course there will be excessive distortion! Just venting some frustration:mad:. Ive defined my rubber much like how Jorgen used. Im the strain energy option is not the right one or my coefficients need to be higher with how much pressure im subjecting the block too. Here is my inp file. If anyone can look at it and give me anything feedback I would greatly apreciate it.

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