[Solved] 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.

how to start with vumat?

Hi, Jorgen,

you have been saying that the book Introduction to the computational plasticity contains codes on vumat? But I didnt 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 dont 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 dont know how to start with. how to understand vumat better.

Best Regards,

Jingfen