View Full Version : Re: Abaqus bilinear material

10-12-1999, 06:43 PM
At 10:17 AM 10/12/99 -0500, you wrote:
>Would anyone have any information on how to implement a bilinear material
>definition in Abaqus?
>The only way I am aware of is through the use of a user-defined material
>(UMAT). But, I am unsure of how to code the material definition. Could
>someone who has coded something similar please offer some assistance? Or,
>if there is alternative method.
>The data I am working with is the value of the Young's modulus of
>elasticity corresponding to a region of strain and an additional value of
>the Young's modulus for the second region of strain through failure/maximum
>Thanks in advance for any feedback
>Brad Probst
>Dept. of Biomedical Eng.
>Tulane University


I see a couple of replies advising using *ELASTIC and *PLASTIC but be
careful there. Two questions: is your material elastic up to failure of
does it actually go plastic? It won't matter if the loading is monotonic
everywhere. If not, and some of it unloads, then *PLASTIC won't give the
right response.

I also see that you're in a biomedical department. If you're working with
a nonlinear elastic biomaterial then *HYPERELASTIC may be your best bet up
to the point of failure. If you want to allow it to damage and fail, you
may need to use UMAT. However I find VUMAT, as found in Abaqus/Explicit,
easier to code.



PS I've also posted this to sports-engineering@mailbase.ac.uk. There are
subscribers there who're at the interface between engineering and bio-stuff.

Dr R D Thomson
Ballistics, Impact + Sports Eng Group
Mech Eng Dept, Glasgow Uni
Glasgow G12 8QQ, Scotland

tel UK (44) Gla (141) 330 4313
fax UK (44) Gla (141) 330 4343
web http://www.mech.gla.ac.uk/~rthomson

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