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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
Elasto-plastic Materials
These materials can be used to represent elasto-plastic materials.

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.
  - 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.
      - /MAT/LAW2 (PLAS_JOHNS)
        Block Format Keyword This law represents an isotropic elasto-plastic material using the Johnson-Cook material model.
      - /MAT/PLAS_ZERIL
        Block Format Keyword This law defines an isotropic elasto-plastic material using the Zerilli-Armstrong plasticity model.
      - /MAT/LAW3 (HYDPLA)
        Block Format Keyword This law represents an isotropic elasto-plastic material using the Johnson-Cook material model.
      - /MAT/LAW4 (HYD_JCOOK)
        Block Format Keyword This law represents an isotropic elasto-plastic material using the Johnson-Cook material model. This model expresses material stress as a function of strain, strain rate and temperature.
      - /MAT/LAW16 (GRAY)
        Block Format Keyword This material law is based on Gray EOS and Johnson-Cook yield criteria.
      - /MAT/LAW22 (DAMA)
        Block Format Keyword This law is identical to Johnson-Cook material (/MAT/LAW2), except that the material undergoes damage if plastic strains reach a user-defined value ( $ε_{d a m}$ ). This law can be applied to both shell and solid elements.
      - /MAT/LAW23 (PLAS_DAMA)
        Block Format Keyword This law models an isotropic elastic plastic material and combines Johnson-Cook material model with a generalized damage model. The law is applicable only for solid elements.
      - /MAT/LAW27 (PLAS_BRIT)
        Block Format Keyword This law combines an isotropic elasto-plastic Johnson-Cook material model with an orthotropic brittle failure model. Material damage is accounted for prior to failure. Failure and damage occur only in tension. This law is applicable only for shells.
      - /MAT/LAW32 (HILL)
        Block Format Keyword This law describes the Hill orthotropic plastic material. It is applicable only to shell elements. This law differs from LAW43 (HILL_TAB) only in the input of yield stress.
      - /MAT/LAW36 (PLAS_TAB)
        Block Format Keyword This law models an isotropic elasto-plastic material using user-defined functions for the work-hardening portion of the stress-strain curve (for example, stress versus plastic strain) for different strain rates.
      - /MAT/LAW43 (HILL_TAB)
        Block Format Keyword This law describes the Hill orthotropic material and is applicable only to shell elements. This law differs from LAW32 (HILL) only in the input of yield stress (here it is defined by a user function).
      - /MAT/LAW44 (COWPER)
        Block Format Keyword The Cowper-Symonds law models an elasto-plastic material. The basic principle is the same as the standard Johnson-Cook model; the only difference between the two laws lies in the expression for strain rate effect on flow stress.
      - /MAT/LAW48 (ZHAO)
        Block Format Keyword This law describes the Zhao material law used to model an elasto-plastic strain rate dependent materials. The law is applicable only for solids and shells.
      - /MAT/LAW49 (STEINB)
        Block Format Keyword Defines an elastic plastic material with thermal softening.
      - /MAT/LAW52 (GURSON)
        Block Format Keyword This law is based on the Gurson constitutive law, which is used to model visco-elastic-plastic strain rate dependent porous metals.
      - /MAT/LAW53 (TSAI_TAB)
        Block Format Keyword Describes the law that is a uni-directional orthotropic elasto-plastic law and is only used with solid elements.
      - /MAT/LAW57 (BARLAT3)
        Block Format Keyword This law describes plasticity hardening by a user-defined function and can be used only with shell elements.
      - /MAT/LAW60 (PLAS_T3)
        Block Format Keyword This law models an isotropic elasto-plastic material using user-defined functions for the work-hardening portion of the stress-strain curve (that is, plastic strain versus stress) for different strain rates.
      - /MAT/LAW63 (HANSEL)
        Block Format Keyword This law describes the trip steel plastic material. This material law can be used only with shell elements.
      - /MAT/LAW64 (UGINE_ALZ)
        Block Format Keyword This law describes the Ugine & Alz trip steel material. This material law can be used only with shell elements.
      - /MAT/LAW65 (ELASTOMER)
        Block Format Keyword This law describes nonlinear elasto-plastic material with strain rate dependent loading and unloading behavior.
      - /MAT/LAW66
        Block Format Keyword This law models an isotropic tension-compression elasto-plastic material law using user-defined functions for the work-hardening portion of the stress-strain (plastic strain versus stress). This law can be defined for compression and tension.
      - /MAT/LAW72 (HILL_MMC)
        Block Format Keyword Describes the anisotropic Hill material with a modified Mohr fracture criteria. This law is available for shell and solid.
      - /MAT/LAW73
        Block Format Keyword This law describes the Thermal Hill orthotropic material and is applicable only to shell elements.
      - /MAT/LAW74
        Block Format Keyword This law describes the Thermal Hill orthotropic 3D material and is applicable only to solid elements. The yield stress may depend on strain rate, or on both strain rate and temperature.
      - /MAT/LAW76 (SAMP)
        Block Format Keyword This law describes a semi-analytical elasto-plastic material using user-defined functions for the work-hardening portion for tension, compression and shear (stress as function of strain).
      - /MAT/LAW78
        Block Format Keyword This law is the Yoshida-Uemori model for describing the large-strain cyclic plasticity of metals. The law is based on the framework of two surfaces theory: the yielding surface and the bounding surface.
      - /MAT/LAW79 (JOHN_HOLM)
        Block Format Keyword This material law describes the behavior of brittle materials, such as ceramics and glass. The implementation is the second Johnson-Holmquist model: JH-2.
      - /MAT/LAW80
        Block Format Keyword This law allows modeling the ultra-high strength steel behavior at high temperatures and the phase transformation phenomena from austenite to ferrite, pearlite, bainite and martensite during cooling.
      - /MAT/LAW84
        Block Format Keyword Swift-Voce elastoplastic law with Johnson-Cook strain rate hardening and temperature softening. This law allows modeling a quadratic non-associated flow rule.
      - /MAT/LAW87 (BARLAT2000)
        Block Format Keyword This elasto-plastic law is developed for anisotropic materials, especially aluminum alloys.
      - /MAT/LAW93 (ORTH_HILL) or (CONVERSE)
        Block Format Keyword This law describes the orthotropic elastic behavior material with Hill plasticity and is applicable to shell and solid elements (/BRICK, /TETRA4 and /TETRA10).
      - /MAT/LAW103 (HENSEL-SPITTEL)
        Block Format Keyword This law represents an isotropic elastic-plastic material at high temperature using Hensel-Spittel yield stress formula. The yield stress is a function of strain, strain rate and temperature. This material law can be used with an equation of state /EOS.
      - /MAT/LAW104 (JOHNS_VOCE_DRUCKER)
        Block Format Keyword An elasto-plastic constitutive material law using the 6^th order Drucker model with a mixed Voce and linear hardening.
      - /MAT/LAW106 (JCOOK_ALM)
        Block Format Keyword This law represents an isotropic elasto-plastic material using the Johnson-Cook material model. This model expresses material stress as a function of strain and temperature.
      - /MAT/LAW109
        Block Format Keyword Elasto-plastic material with isotropic von Mises yield criterion with plastic strain rate and temperature depending nonlinear hardening.
      - /MAT/LAW110 (VEGTER)
        Block Format Keyword Elasto-plastic constitutive law using the interpolated yield criterion of Corus-Vegter and the hardening law of Vegter, accounting for strain rate dependency and thermal effect.
      - /MAT/LAW112 (PAPER or XIA)
        Block Format Keyword The Paperboard law models an orthotropic and dissymmetric elasto-plastic material from proposed by Xia, 2002.
      - /MAT/LAW115 (DESHFLECK)
        Block Format Keyword An elasto-plastic constitutive law using von Mises criterion with pressure dependence. The hardening law is linear – nonlinear with an increasing exponential hardening.
      - /MAT/LAW120 (TAPO)
        Block Format Keyword This is a non-associated elasto-plastic model for polymer adhesives. The constitutive model is based on a I1-J2 criterion that can be reduced either to a von Mises or Drucker-Prager type in compression.
      - /MAT/LAW121 (PLAS_RATE)
        Block Format Keyword Elasto-plastic strain-rate dependent material with isotropic von Mises yield criterion. This material law is available for both solids and shells.
      - /MAT/PLAS_PREDEF
        Block Format Keyword This material law has predefined elasto-plastic data for some common steel, aluminum, and plastic materials.
      - /NONLOCAL/MAT
        Block Format Keyword Non-local regularization for elasto-plastic failure criteria (as in, dependent to plastic strain) and shell thickness variation.
    - 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.
    - 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.

Elasto-plastic Materials

These materials can be used to represent elasto-plastic materials.