2018/11/2 1.2.20 VUMAT
http://ivt-abaqusdoc.ivt.ntnu.no:2080/v6.14/books/sub/default.htm?startat=ch01s01asb41.html#sub-xsl-umat 1/12
1.2.20 VUMAT
User subroutine to define material behavior.
Product: Abaqus/Explicit
Warning: The use of this user subroutine generally requires considerable expertise. You are
cautioned that the implementation of any realistic constitutive model requires extensive
development and testing. Initial testing on a single-element model with prescribed traction
loading is strongly recommended.
The component ordering of the symmetric and nonsymmetric tensors for the three-dimensional
case using C3D8R elements is different from the ordering specified in “Three-dimensional solid
element library,” Section 28.1.4 of the Abaqus Analysis User's Guide, and the ordering used in
Abaqus/Standard.
References
“User-defined mechanical material behavior,” Section 26.7.1 of the Abaqus Analysis User's Guide
*USER MATERIAL
Overview
User subroutine VUMAT:
is used to define the mechanical constitutive behavior of a material;
will be called for blocks of material calculation points for which the material is defined in a user
subroutine (“Material data definition,” Section 21.1.2 of the Abaqus Analysis User's Guide);
can use and update solution-dependent state variables;
can use any field variables that are passed in; and
can be used in an adiabatic analysis, provided you define both the inelastic heat fraction and the specific
heat for the appropriate material definitions and you store the temperatures and integrate them as user-
defined state variables.
Component ordering in tensors
The component ordering depends upon whether the tensor is symmetric or nonsymmetric.
Symmetric tensors
For symmetric tensors such as the stress and strain tensors, there are ndir+nshr components, and the
component order is given as a natural permutation of the indices of the tensor. The direct components are first
and then the indirect components, beginning with the 12-component. For example, a stress tensor contains
ndir direct stress components and nshr shear stress components, which are passed in as
Component 2D Case 3D Case
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