USERMAT allows you to define a material's mechanical behavior for an ANSYS simulation.
Helius PFA has the capability to forward on to the custom ANSYS user subroutine USERMAT. In other words, you can use Helius PFA in conjunction with the ANSYS USERMAT subroutine.
The USERMAT subroutine can be used to define the mechanical constitutive behavior of a material and to update solution-dependent state variables. Refer to the ANSYS Documentation for further details.
To use the USERMAT subroutine with Helius PFA, you need to include USERMAT with the Helius PFA subroutine build. Those instructions can be found here. In addition, you must set the USER_ID_LO and USER_ID_HI environment variables in the hpfa.env file. These variables will tell Helius PFA the range of ANSYS material IDs to forward to your USERMAT subroutine. For example:
&HPFA_ENV
MATERIAL_FILE_DIR = 'C:\Program Files\Autodesk\Helius PFA 20XX.X\Materials'
USER_ID_LO = 100
USER_ID_HI = 110
/In the example hpfa.env file above, any ANSYS material ID between 100 and 110 (inclusive) will be passed to your custom USERMAT.