UMAT allows you to define a material's mechanical behavior for an Abaqus/Standard analysis.
Helius PFA has the capability to forward on to the custom Abaqus user subroutine UMAT. In other words, you can use Helius PFA in conjunction with the Abaqus UMAT subroutine.
The UMAT 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 UMAT subroutine with Helius PFA, you need to include UMAT 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 UMAT, 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 UMAT.