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Radioss 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.
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.
Shell Animations
/ANIM/SHELL/IDPLY/PHI
Engine Keyword Generates animation files containing angle between element skew and direction 1 orthotropy.

Welcome
What's New
View new features for Radioss 2026.
Radioss Overview
Radioss is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
Radioss User Guide
This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
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 2026
  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.
    - Nodal Animations
    - Element Animations
    - Brick Animations
    - Shell Animations
      - /ANIM/SHELL/Restype
        Engine Keyword Generates animation files containing shell element data for the specified result. Options used for SHELL type of element.
      - /ANIM/SHELL/DAMA
        Engine Keyword Generates animation files containing a damage value for each layer of a shell element. The damage value is the maximum of damage over time of all failure criteria associated to the material.
      - /ANIM/SHELL/EPSP
        Engine Keyword Generates animation files containing plastic strain as function of a shell element integration point.
      - /ANIM/SHELL/FLDF
        Engine Keyword Generates animation files containing the FLD damage factor for the FLD failure model.
      - /ANIM/SHELL/FLDZ
        Engine Keyword Generates animation files containing the FLD failure zone factor for the FLD failure model as function of a shell element integration point.
      - /ANIM/SHELL/IDPLY
        Engine Keyword Generates animation files containing integer value, defining if a shell belong to a given ply.
      - /ANIM/SHELL/IDPLY/Restype
        Engine Keyword Generates animation files containing shell tensor data for shell elements that use ply based composite properties, /PROP/STACK (TYPE17), /PROP/TYPE51, or /PCOMPP.
      - /ANIM/SHELL/IDPLY/DAMA
        Engine Keyword Generates animation files containing damage values for shell elements that use ply based composite properties, /PROP/STACK (TYPE17), /PROP/TYPE51, or /PCOMPP. The damage value is the maximum of damage over time and of all failure criteria associated to the material.
      - /ANIM/SHELL/IDPLY/EPSP
        Engine Keyword Generates animation files containing plastic strain for shell elements that use ply-based composite properties, /PROP/STACK (TYPE17), /PROP/TYPE51, or /PCOMPP.
      - /ANIM/SHELL/IDPLY/PHI
        Engine Keyword Generates animation files containing angle between element skew and direction 1 orthotropy.
      - /ANIM/SHELL/NXTFACTOR
        Engine Keyword Generates animation files containing the instability factor of NXT failure model as function of a shell element integration point.
      - /ANIM/SHELL/PHI
        Engine Keyword Generates animation files containing angle between element skew and direction 1 orthotropy.
      - /ANIM/SHELL/SIG1H
        Engine Keyword Generates animation files containing the first normalized principal stress as function of a shell element integration point.
      - /ANIM/SHELL/SIG2H
        Engine Keyword Generates animation files containing the second normalized principal stress as function of a shell element integration point.
      - /ANIM/SHELL/TDEL
        Engine Keyword Generates animation output for the time at which a shell element is deleted. The rupture time is output only for elements which are deleted, due to a /FAIL criterion. Failure criteria built in materials are ignored.
      - /ANIM/SHELL/TENS
        Engine Keyword Generates animation files containing shell tensor data for a specified result.
    - Other Animations
    - Curve Plots
      Engine Keyword
    - H3D Output
    - Other Output Files
      Engine Keyword
  - 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
Radioss Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Radioss Verification Problems
This manual presents solved verification models.
Radioss Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Radioss Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
Radioss User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

/ANIM/SHELL/IDPLY/PHI

Engine Keyword Generates animation files containing angle between element skew and direction 1 orthotropy.

Format

/ANIM/SHELL/IDPLY/PHI/Keyword5

Definition


Field	Contents	SI Unit Example
`Keyword5`	Ply ID number: I Ply ID I ALL All the plies.