Crushable Foam Model in CalculiX

1

Hi

Has anyone used Crushable foam model in CalculiX? (Also called as Deshpande Fleck model)
I found that CalculiX does not have this material model inbuilt in it like ABAQUS.

I plan to write a UMAT for it and implement it in CalculiX.
Any suggestions on how to start?

I am not looking for the complete UMAT code itself, rather I’d like to discuss/get help on how to write it from scratch.

Thanks

2

I haven’t used the crushable foam model.
You could start with the UMAT subroutines for the card *HYPERFOAM - I think that would give you a good start.

3

Thanks.
This is for rubber-type materials I believe.

Anyway, let me see how it goes.

4

I think it would be a good idea to create a UMAT subroutine based on *HYPERFOAM, but if ABAQUS has a “Crushable foam model” or “Deshpan de Fleck model”, I think it is better to create a UMAT subroutine based on them, if we can read the source code of them.

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5

Thanks for this.

Unfortunately, we don’t have the access to ABAQUS source files (except the documentation/theory manual).

Bhanu

6

Hi

I feel this is a silly question, but anyway, let me post it:
Can anyone clarify whether the Deshpande Fleck Model (*CEUSHABLE FOAM) in ABAQUS, accounts for rate effects or not?

(As per ABAQUS documentation, there is an option of including rate effects using a separate card *RATE DEPENDENT, but the crushable foam model as such does not ask for any other inputs other than the quasi-static cauchy-stress–true-strain hardening data.)

Another question, does CalculiX have any way of including rate effects?

Bhanu

7

As you said, in Abaqus you have to add the *RATE DEPENDENT keyword to account for strain rate dependence. Constants for it are specified under this keyword, not under the material model keyword.

From what I know, CalculiX doesn’t have built-in strain rate dependence and you would need UMAT to include it.

8

Does it make the Crushable Foam model a rate-independent model as such? I mean the constitutive model itself. (I am a little confused here)

9

Yes, that’s right. Check the Abaqus documentation chapters “Crushable foam plasticity models” and “Models for crushable foams”. They discuss this material model in detail, including equations.

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