In Abaqus/Standard you can introduce dependence on solution variables with user subroutine USDFLD. This subroutine allows you to define field variables at a material point as functions of time, of any of the available material point quantities listed in Abaqus/Standard output variable identifiers, and of material directions. Material properties defined as functions of these field variables may, thus, be dependent on the solution.
Context:
User subroutine USDFLD is called at each point for which the material definition includes a reference to the user subroutine.
From the menu bar in the Edit Material dialog box, select GeneralUser Defined Field.
Click OK to close the Edit Material dialog box. Alternatively, you can select another material behavior to define from the menus in the Edit Material dialog box (see Browsing and modifying material behaviors, for more information).