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User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.
Global User Window
With Radioss, it is possible to define a global user window. This is the most general interface between Radioss and external code.
USERWI Engine Interface Routines

Welcome
What's New
View new features for Radioss 2025.
Overview
Radioss^® is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Verification Problems
This manual presents solved verification models.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.
- Global User Window
  With Radioss, it is possible to define a global user window. This is the most general interface between Radioss and external code.
  - Starter Subroutine USERWIS_INI
    This subroutine reads input data and prepares the Radioss buffers for allocation.
  - Starter Subroutine USERWIS
    This subroutine reads the input data.
  - USERWIS Starter Interface Subroutines
  - Engine Subroutine USERWI
    This subroutine calculates the internal forces and moments versus the velocity, old forces and moments, and specified variables and parameters.
  - USERWI Engine Interface Routines
- Material Laws 29, 30, 31
  Up to 3 material user’s laws (law 29, 30 and 31) can be defined for 3D, 2D solid elements and 3D shell elements. User’s laws for beam or truss elements are not available.
- Extended Material Laws
  In Radioss, 99 material user laws can be defined for 3D and 2D solid elements, connection element, and 3D shell elements.
- User Property Elements
  Up to 3 spring user properties (property number 29, 30, and 31) can be defined for spring and solid elements.
- User Sensors
  In Radioss, up to three types of user sensors can be defined.
- User Failure Models
  In Radioss up to 3 user’s failure models (USER1, USER2, and USER3) can be defined for shell and solid elements.
- Write in Output Files
  Some user subroutines do not pass the IOUT file descriptor and, thus, do not permit writing in a Radioss output file.
- Generate Radioss User Libraries
  Radioss user libraries are built on Windows and Linux with two different compilers: Intel Fortran or Gfortran.
- Initialize, Verify and Finalize
  The workflow in some user options may require initialization, verify during the run and finalize tasks in the Engine.
- Appendix

USERWI Engine Interface Routines

GET_USER_WINDOW_NODES (INTERNAL_ID, USER_ID)

Get the list of nodes involved in the User Windows as internal ID and input deck ID. The arrays must be initialized and have the size of all the nodes involved in the User Windows as defined in Starter.

USERWINDOW_GET_A(A_BUF)

Gets the node forces from previous explicit cycle.

A_BUF: A 3xNUMNOD array must be allocated before calling the routine.

USERWINDOW_GET_AR(AR_BUF)

Gets the nodal moments from previous explicit cycle.

AR_BUF: A 3xNUMNOD array must be allocated before calling the routine.

Example Demo File

Before you begin, copy the file(s) used in this problem to your working directory.

1_global_user_window.zip