VUMAT allows you to define a material's mechanical behavior for an Abaqus/Explicit analysis.
Helius PFA has the capability to forward on to the custom Abaqus user subroutine VUMAT. In other words, you can use Helius PFA in conjunction with the Abaqus VUMAT subroutine.
The VUMAT subroutine can be used to define the mechanical constitutive behavior of a material and to update solution-dependent state variables. Refer to the Abaqus Documentation for further details.
To use the VUMAT subroutine with Helius PFA, you need to include VUMAT with the Helius PFA subroutine build. Those instructions can be found here for Windows or here for Linux. In addition, you must set the USER_PREFIX environment variable in the hpfa.env file. This variable will allow Helius PFA to recognize a material with a given prefix and forward it to your VUMAT, rather than process it as a Helius PFA user material. For example:
&HPFA_ENV MATERIAL_FILE_DIR = 'C:\Program Files\Autodesk\Helius PFA 2016\Materials' USER_PREFIX = 'EXAMPLE_' /
In the example hpfa.env file above, any material name that begins with EXAMPLE_ will be passed to your custom VUMAT.