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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.
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.
Implicit Solvers
Engine Keyword
/IMPL/LINEAR
Engine Keyword Linear implicit solution will be computed.

Welcome
What's New
View new features for Radioss 2024.1.
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.
- 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 2024
  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.
  - 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.
    - Implicit Controls
      Engine Keyword
    - Implicit Solvers
      Engine Keyword
      - /IMPL/BUCKL/1
        Engine Keyword Euler buckling modes will be computed.
      - /IMPL/BUCKL/2
        Engine Keyword Euler buckling modes will be computed based on actual pre-stress stat.
      - /IMPL/LBFGS/L
        Engine Keyword Change the maximum number of BFGS quasi-Newton method for implicit nonlinear.
      - /IMPL/LINEAR
        Engine Keyword Linear implicit solution will be computed.
      - /IMPL/LRIGROT
        Engine Keyword Due to some linearization used in geometrical nonlinear analysis, small time step has to be chosen to avoid accumulated errors under large rotation. In this case, this option improves the accuracy using usual time step.
      - /IMPL/NONLIN/N
        Engine Keyword Nonlinear implicit methods.
      - /IMPL/NONLIN/SMDISP
        Engine Keyword Only small displacement effects will be considered with this option.
      - /IMPL/NONLIN/SOLVINFO
        Engine Keyword Output global solve information at each solving iteration.
      - /IMPL/QSTAT
        Engine Keyword Quasi-static implicit solution will be computed.
      - /IMPL/QSTAT/DTSCAL
        Engine Keyword Quasi-static implicit solution with a factor for inertia stiffness matrix.
      - /IMPL/QSTAT/MRIGM
        Engine Keyword Rigid motion has been removed or minimized from quasi-static implicit solution.
      - /IMPL/SOLVER
        Engine Keyword Selects linear solver.
    - Implicit Time Step
      Engine Keyword
    - Implicit Model Check
      Engine Keyword
    - Implicit Output Messages
      Engine Keyword
  - 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).
  - Obsolete
    Engine Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- LS-DYNA Input
  This manual provides a list of LS-DYNA input files available in Radioss.
- Optimization Keywords
  Optimization Keyword This manual contains the description of the keywords for the Radioss optimization. This manual is compatible with the version 2018 of Radioss.
- Multi-Domain
  This manual contains the description of the keywords for the Radioss Multi-Domain.
- 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
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.

/IMPL/LINEAR

Engine Keyword Linear implicit solution will be computed.

Format

/IMPL/LINEAR

Comments

Required for linear statics, normal modes and linear buckling solution.