Home
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 Time Step
Engine Keyword
/IMPL/DT/1
Engine Keyword Implicit time step control method 1.

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.
- 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
    - Implicit Time Step
      Engine Keyword
      - /IMPL/DT/1
        Engine Keyword Implicit time step control method 1.
      - /IMPL/DT/2
        Engine Keyword Implicit automatic time step control method 2.
      - /IMPL/DT/3
        Engine Keyword Implicit automatic time step control with Riks method.
      - /IMPL/DT/FIXPOINT
        Engine Keyword Users' input fix time points where implicit nonlinear computation will not miss with automatic time step control.
      - /IMPL/DT/STOP
        Engine Keyword The computation will be stopped, if DT_min is reached. If DT_max is reached, the computation will continue with constant time step set as DT_max.
      - /IMPL/DTINI
        Engine Keyword Initial time step for nonlinear implicit analysis.
    - 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/DT/1

Engine Keyword Implicit time step control method 1.

Format

/IMPL/DT/1

lt_w $Δ T_{s c a_i}$ L_dtn $Δ T_{s c a_d}$

Definition


Field	Contents	SI Unit Example
`lt_w`	If the solution of a time step converges within `It_w` iterations, the next time step will be increased by a factor of $Δ T_{s c a_i}$ . = 0 Set to 2
$Δ T_{s c a_i}$	Scale factor for increasing the time step. = 0 Set to 1.1
`L_dtn`	Maximum number of iterations before resetting and decreasing the time step by a factor of $Δ T_{s c a_d}$ . = 0 Set to 15
$Δ T_{s c a_d}$	Scale factor for decreasing the time step. = 0 Set to 0.67

Comments

If /IMPL/DT/1, /IMPL/DT/2, or /IMPL/DT/3 are not present, the only time step controls are /IMPL/NCYCLE/STOP and /IMPL/DT/STOP. In the case of divergence, the time step will be reduced by half and repeated.