# Thread: Exemplar UMAT and VUMAT Subroutines for ABAQUS

1. ## Exemplar UMAT and VUMAT Subroutines for ABAQUS

If you are interested in learning about how to write user material subroutines for finite element programs then you might want to check out the the recent book "Introduction to Computational Plasticity" by F. Dunne and N. Petrinic (Oxford University Press, 2005). This book is one of the very few that actually discusses user material implementations in Fortran. It is particularly interesting to note that the book gives complete UMAT and VUMAT examples for ABAQUS, and that the exemplar code can be downloaded from the Oxford University Press website.

I have no connection with the authors and I have not examined or tested the subroutines that they present. It seems, however, that the book and the accompanying code examples could be useful for students and engineers interested in learning more about constitutive equations and UMAT development.

2. Junior Member
Join Date
2010-10
Posts
18

Hi, Jorgen,

you have been saying that the book "Introduction to the computational plasticity" contains codes on vumat? But I didn't find it. Could you please tell me which pages containing this information?

besides, I am not quite understanding the explanations on vectorized interface in some abaqua documents as follows.

VUMAT formulation aspects
 Vectorized interface
 In VUMAT the data are passed in and out in large blocks (dimension
nblock). nblock typically is equal to 64 or 128.
 Each entry in an array of length nblock corresponds to a single
material point. All material points in the same block have the same material name and belong to the same element type.
 This structure allows vectorization of the routine.
 A vectorized VUMAT should make sure that all operations are done in vector mode with nblock the vector length.
 In vectorized code branching inside loops should be avoided.
 Element type based branching should be outside the nblock loop.

Actually, all what are saying here, I am not so understand. especially the term "block" here. Maybe it is because I don't have some basic idea of vectorization. and how abaqus store the data for the vumat. could you please recommend some books on vectorization for me to start with? and tell me something to be careful when writing vumat. I have been sucessfully past the UMAT for my proposed material model. Currently, I am going to convert this umat into vumat so that it is able to analyse dynamic examples. But it looks like for me the vumat is more difficult. I don't know how to start with. how to understand vumat better.

Best Regards,
Jingfen

3. Junior Member
Join Date
2010-10
Posts
18
Dear Jorgen,

I couldn't see the examples of vumat in this book. could you please tell me which pages gives examples of vumat in this book?

Thank you so much.

Best regards,
Jingfen

4. Junior Member
Join Date
2012-02
Posts
7
Hi Jorgen
I also could not find the books and the examples. It seams that the links has been removed.
Do you have any new link for that¨.

Thanks
Regards
Ali

5. It appears that those files are no longer available for download...

-Jorgen

6. Junior Member
Join Date
2012-02
Posts
4

## Link for the fortran codes mentioned in the book

Originally Posted by Jorgen

-Jorgen
http://www.eng.ox.ac.uk/NP/ICP/

I have just downloaded all files using the link given above. I hope it works for you as well.

7. Junior Member
Join Date
2012-02
Posts
7
thanks a lot for the new web address

8. Junior Member
Join Date
2012-02
Posts
4
No problem at all. I think the book itself is a bit difficult to understand when it comes to the 2nd part (from 7th chapter to the end), but the first 6 chapters are really helpful to understand the basics of plasticity (particularly metal plasticity) and chapter 5 is really good to understand the difference between explicit and implicit stress integration algorithms.

By the way, "Computational Methods for Plasticity-Theory and Applications" is also a very good reference for those who want to see some pseudo codes while implementing umat(s)/vumat(s).

9. Junior Member
Join Date
2012-02
Posts
7
thanks for introducing "Computational Methods for Plasticity-Theory and Applications" book, It also have good explanation for anisotropic plasticity that was really useful for me.

10. Junior Member
Join Date
2012-05
Posts
12
Attached find the:

2) All the codes on the web site
3) PDF list of the codes in the ZIP file.

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