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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
Starter Input
This manual provides a list of all the model definition keywords and options available in Radioss.
Materials
Composite and Fabric Materials
These materials can be used to represent composite and fabric materials.
/MAT/LAW25 (COMPSH)
Two variations of the same material law type 25 are implemented: Tsai-Wu formulation and CRASURV formulation.

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.
  - 2D and 3D Analysis Options
  - Starter Keywords Syntax
    Block Format Keyword
  - Smooth Particle Hydrodynamics (SPH)
    The Smooth Particle Hydrodynamics method formulation is used to solve the equations of mechanics, when particles are free from a meshing grid.
  - Computational Fluid Dynamics (CFD)
  - General Controls
    Block Format Keyword In this group, keywords are used to set default value, global parameter, analysis type, input/output print, damping and ALE and CFD treatment for the whole model. For default value, it is still possible to overwrite in each specific keywords.
  - Nodes
    Block Format Keyword In Radioss, two node types are available. They use Cartesian coordinate to describe the position of each node.
  - Elements
    Block Format Keyword
  - Component and Parts Organization
    Block Format Keyword In this group, keywords are used to combine material and property information (/PART), assemble model (/SUBSET) or define a separate model (//SUBMODEL).
  - Interfaces
    Block Format Keyword Interfaces solve the contact and impact conditions between two parts of a model. Several interface types are available in Radioss and use different contact treatments.
  - Materials
    - Material Compatibility
      Block Format Keyword The following tables list the compatibility options for each of the material laws.
    - Elasto-plastic Materials
      These materials can be used to represent elasto-plastic materials.
    - Hyper and Visco-elastic Materials
      These materials can be used to represent hyper and visco-elastic materials.
    - Composite and Fabric Materials
      These materials can be used to represent composite and fabric materials.
      - /MAT/LAW12 (3D_COMP)
        Block Format Keyword This law describes a solid material using the Tsai-Wu formulation that is usually used to model composites. This material is assumed to be 3D orthotropic-elastic before the Tsai-Wu criterion is reached.
      - /MAT/LAW14 (COMPSO)
        Block Format Keyword This law describes an orthotropic solid material using the Tsai-Wu formulation that is mainly designed to model uni-directional composites. This material is assumed to be 3D orthotropic-elastic before the Tsai-Wu criterion is reached. The material becomes nonlinear afterwards.
      - /MAT/LAW15 (CHANG)
        Block Format Keyword This law is used to model composite shell elements, similar to LAW25. The plastic behavior is based on the Tsai-Wu criteria (/MAT/LAW25 (COMPSH) for Tsai-Wu description) and failure is based on the Chang-Chang failure criterion is used.
      - /MAT/LAW19 (FABRI)
        Block Format Keyword This law defines an elastic orthotropic material and is available only for shell elements. It is used to model airbag fabrics.
      - /MAT/LAW25 (COMPSH)
        Two variations of the same material law type 25 are implemented: Tsai-Wu formulation and CRASURV formulation.
        Tsai-Wu Formulation (I_form =0)
        Block Format Keyword This law describes the composite shell and solid material using the Tsai-Wu formulation.
        CRASURV Formulation (I_form= 1)
        Block Format Keyword This law describes the composite shell and solid material using the CRASURV formulation.
      - /MAT/LAW58 (FABR_A)
        Block Format Keyword This law describes a hyperelastic anisotropic fabric material. It uses an anisotropic coordinate system with an anisotropy angle, following element deformation.
      - /MAT/LAW114 (SPR_SEATBELT)
        Block Format Keyword This spring material is designed for 1D seatbelt elements.
      - /MAT/LAW119 (SH_SEATBELT)
        Block Format Keyword This orthotropic shell material is designed for 2D seatbelt element.
      - /MAT/LAW122 (MODIFIED_LADEVEZE)
        Block Format Keyword A simple unidirectional composite ply model, accounting for orthotropic elasticity and plasticity. Fiber and matrix damage are considered, including strain rate effect.
    - Multiscale Materials
    - Concrete and Rock Materials
      In Radioss these materials can be used to represent rock or concrete materials.
    - Honeycomb Materials
      These materials can be used to represent honeycomb materials.
    - Connection Materials
      These materials can be used to represent connection materials.
    - Other Materials
      These materials can be used to represent other materials.
    - Multi-Material, Fluid and Explosive Materials
      These materials can be used to represent multi-material, fluid and explosive materials.
    - ALE and CFD Options
      Block Format Keyword ALE and CFD options used to activate ALE formulation or Eulerian formulation for a given material law.
    - Viscosity Option
    - Leakage Option
    - Thermal Option
    - Equation of State
      Used by Radioss to compute the hydrodynamic pressure.
    - Failure Models
      The supported failure models in Radioss.
  - Properties
    Block Format Keyword
  - Monitored Volumes (Airbags)
    Block Format Keyword Monitored volumes can be used to model an airbag, tire, tank, or any closed volume.
  - Constraints
    Block Format Keyword Radioss supports several different kinematic constraints, which are mainly used to impose acceleration, velocity, displacement or temperature in structure or constraint the moving of structure. They are mutually exclusive for each degree-of-freedom (DOF). Two kinematic conditions applied to the same node may be incompatible.
  - Load Cases
    Block Format Keyword In Radioss the following load cases are available. Stress/strain as initial state could be considered by modeling, as well as pressure, gravity, and thermal load.
  - Tools
    Block Format Keyword In this group, tools like transformation, frames, skews, and curve are introduced.
  - Groups(Sets)
    Block Format Keyword Keywords in this group are used to define how to select a group of node, part, elements, lines, or surfaces.
  - Adaptive Meshings
    Block Format Keyword Adaptive Meshing is used in metal forming to divide the element to better describe the geometry. /ADMESH/GLOBAL and /ADMESH/SET are not available for SPMD computation.
  - Output Database
    Block Format Keyword Time histories output for different element groups, section output, or gauge output are described in this group.
  - Obsolete
    Block Format Keyword Keywords that are still supported, but no longer maintained (*) are considered obsolete.
- Engine Input
  This manual provides a list of all the solution definition keywords and options available in Radioss.
- 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.

/MAT/LAW25 (COMPSH)

Two variations of the same material law type 25 are implemented: Tsai-Wu formulation and CRASURV formulation.

If the formulation flag I_form (Line 2, field 7) is set to 0, the plasticity model is based on standard (Tsai-Wu) formulation is used. Refer to the /MAT/LAW25 (Tsai-Wu Formulation (Iform =0)) keyword.
If the formulation flag I_form (Line 2, field 7) is set to 1, the plasticity model is based on CRASURV formulation is used. Refer to the /MAT/LAW25 (CRASURV Formulation (Iform= 1)) keyword.