## Chapter 1: User Subroutine Tutorial Introduction

This manual shows you how to create and use your own user subroutines in Autodyn. Topics covered include:

- How to invoke the user subroutines from Input

- Compiling and linking user subroutines

- Writing your own user subroutines

- Description of Autodyn module variables

Autodyn provides you with a number of standard alternatives for options such as Equations of State, Yield Models, Boundary Conditions, and so on. However, you may wish to use your own custom models for these options. Autodyn allows you to do this by including your own subroutines written in Fortran. This tutorial shows you how to include these subroutines in your calculations and offers guidelines on writing user subroutines. Table 1.1: Material Modeling User Subroutines and Table 1.2: Additional User Subroutines show the user subroutines that are available for use with Autodyn.

Table 1.1: Material Modeling User Subroutines

MDEOS_USER_1 | Custom equation of state (Previously EXEOS)
MDSTR_USER_1 | Custom yield and/or shear model (Previously EXYLD)
MDFAI_USER_1 | Custom failure criteria (Previously EXFAIL / EXFAILS)
MDERO_USER_1 | Custom erosion criteria (Previously EXEROD)
EXBULK | Custom bulk modulus for a linear EOS
EXCOMP | Custom porous compaction curve, P-α equation of state
EXCRCK | Custom tensile crack softening rate
EXDAM | Custom damage parameter
EXPLRN | Custom plastic flow return algorithm
EXSHR | Custom shear modulus
EXSTIF | Custom stiffness matrix, orthotropic-elastic with failure
EXTAB | Custom tabulated saturation curve for two-phase EOS

Table 1.2: Additional User Subroutines

EXACC | Apply user defined acceleration to a Lagrangian node
EXALE | Custom ALE (Arbitrary Lagrange Euler) grid motions
EXEDIT | Custom edits
EXFLOW | Custom Euler flow boundary
EXFOR3 | Custom Force Boundary on structured and unstructured nodes
EXFRICTION | User defined friction
EXLOAD | Loading additional, non-standard data from SAVE files
EXPOR | Custom variable polygon porosity
EXSAVE | Saving additional, non-standard data to SAVE files
EXSIE | Custom energy deposition
EXSTR | Custom stress boundary condition
EXVAL | Custom initial conditions
EXVEL | Custom velocity boundary condition
EXZONE | Custom nodal coordinates
EXORTHO_AXES | Custom define initial material axes for orthotropic materials

Release 18.2 - © ANSYS, Inc. All rights reserved.