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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Engine Input
This manual provides a list of all the solution definition keywords and options available in Radioss.
General Controls
Engine Keyword In this group keywords are used to generally define the output style, control of computation, damping and ALE setup during the computation.
Damping
/ADYREL/1
Engine Keyword Dynamic relaxation with auto-defined adaptive damping applied to node group grnd_ID.

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Radioss^® is a leading explicit finite element solver for crash and impact simulation.
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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.
- File Extensions and Formats
  Current Radioss format uses the 12x extension format.
- Single File Input
  This format allows running either Starter or Engine with the same file.
- New Keywords in 2025
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
  - Engine Keywords Syntax
  - General Controls
    Engine Keyword In this group keywords are used to generally define the output style, control of computation, damping and ALE setup during the computation.
    - Formats
    - Computation
    - Input/Output
    - Damping
      - /ADYREL
        Engine Keyword Dynamic relaxation with auto-defined adaptive damping.
      - /ADYREL/1
        Engine Keyword Dynamic relaxation with auto-defined adaptive damping applied to node group grnd_ID.
      - /DAMP
        Engine Keyword Used to modify the Rayleigh mass and stiffness damping coefficients defined using the Starter /DAMP option.
      - /DYREL
        Engine Keyword Dynamic relaxation.
      - /DYREL/1
        Engine Keyword Dynamic relaxation applied to node group identifier grnd_ID.
      - /KEREL
        Engine Keyword Kinetic energy relaxation.
      - /KEREL/1
        Engine Keyword Kinetic energy relaxation applied to node group grnd_ID.
    - ALE
  - Deletion/Input Modifications
    Engine Keyword In this group, keywords are used for modification (deletion or add options) in Engine.
  - Animation and Post-processing Output Files
    Generates animation files containing results according to the keywords specified. The keywords are specified in the topics within Animation and Post-processing Output Files.
  - Implicit Solution
    Engine Keyword In this group keywords are used for implicit solution. Different implicit solver methods (linear, nonlinear, buckling or quasi-static), different options to control the implicit computation, different implicit time step method and implicit output messages are introduced.
  - Kinematics and Loading
    Engine Keyword In this group, keywords are used to define the kinematic condition (constrain/release rotation or translation DOF) and initial condition (rotational/translational velocity).
  - Time Step
    Engine Keyword In this group, keywords are used to define different time step control (STOP, KILL, CST or DEL, and so on) for different entities (shell, brick, beam, airbag, interface, and so on) during the computation.
  - Initial State
    Engine Keyword In this group, keywords are used to output different info (like stress, strain, orthotropy direction, temperature, and so on) in a state file (STA-File).
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- Obsolete Keywords
  Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Other Files
- Definition
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
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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.

/ADYREL/1

Engine Keyword Dynamic relaxation with auto-defined adaptive damping applied to node group grnd_ID.

Format

/ADYREL/1

grnd_ID

T_start T_stop

Definition


Field	Contents	SI Unit Example
`grnd_ID`	Node group identifier.
`T`_start	(Optional) Start time for Adaptive Dynamic Relaxation. Default = 0.0	$[s]$
`T`_stop	(Optional) Stop time for Adaptive Dynamic Relaxation. Default = Final time of the analysis	$[s]$

Comments

/ADYREL/1 is based on /DYREL but the period to be damped is automatically calculated and varies during the simulation.
The line with T_start and T_stop is optional. If the start and stop times are not included, the adaptive dynamic relaxation is active until the end time defined by /RUN.