## 3.7. Material Modeling User Subroutines

The main material modeling user subroutines (MD_EOS_USER_1.F90, MD_STR_USER_1.F90, MD_FAI_USER_1.F90, MD_ERO_USER_1.F90) have been updated and modularized to allow more flexibility. The table below shows the general description of the usage of the routines, and also the four basic components of each routine:

Routine | Description
--- | ---
Nam_USER_1 | A module to allow the user to define variables that can be defined and accessed in any of the routines below (or anywhere with the USE nam_USER_1 statement)
Init_nam_USER_1 | A subroutine that allows the user to define the input parameters for the material modeling option.
check_nam_USER_1 | A subroutine that allows the user to perform checks on the input data for the user model, during input of the data.
Set_nam_USER_1 | A subroutine to get the material input data from the internal Autodyn data structures and assign local variables as required.
solve_nam_USER_1 | A subroutine in which the user writes his material modeling algorithm

Further details on how to implement material modeling user subroutines are given in the example user subroutine in Subroutine MDSTR_USER_1.

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