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User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.
User Property Elements
Up to 3 spring user properties (property number 29, 30, and 31) can be defined for spring and solid elements.

Welcome
What's New
View new features for Radioss 2024.
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.
- 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.
  - Starter Subroutine LECGnn for Spring and Solid Elements
    This subroutine reads the user property input data. The number of specific property cards and their formats are fixed by the user.
  - Starter Subroutine Initialization RINInn for Spring Elements
    This subroutine initializes the user’s spring element.
  - Starter Subroutine Initialization SINInn for Solid Elements
    This subroutine is used to initialize the user’s solid element (nodal mass and inertia).
  - Engine Subroutine RUSERnn for Spring Elements
    This subroutine calculates the internal forces and moment versus the velocity, old forces, moments, and user’s variables and parameters.
  - Engine Subroutine SUSERnn for Solid Elements
    This subroutine calculates the internal forces and moments.
  - Functions to Access User Properties and Materials
  - User Spring Element Example
    An elastic beam is defined with one user property (TYPE1) with reference to two user properties (TYPE2), one for each beam end. Each secondary user property defines beam geometry and refers to one user material.
  - User Triangular Shell Elements Using Solid Property Example
    A triangular shell property is defined using a user solid property with rotational degrees of freedom at nodes.
- 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

User Property Elements

Up to 3 spring user properties (property number 29, 30, and 31) can be defined for spring and solid elements.

Property type 29 may be referenced as USER1 in Block Format input.

Property type 30 may be referenced as USER2 in Block Format input.

Property type 31 may be referenced as USER3 in Block Format input.

To define a user property, three subroutines for each property must be defined. Two must be linked with Radioss Starter and the other with Radioss Engine.

The Starter subroutine that reads the property data are called LECG29, LECG30, and LECG31. That which initializes spring parameters is called RINI29, RINI30, and RINI31.
The Engine subroutine is called RUSER29, RUSER30, and RUSER31 and computes the spring element forces and moments.

Note: All communication between Radioss and the subroutines takes placed within the argument list.