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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
Other Materials
These materials can be used to represent other materials.
/MAT/LAW0 (VOID)
Block Format Keyword This material can be used to define elements to act as a void, or an empty space.

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.
    - 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.
      - /MAT/LAW0 (VOID)
        Block Format Keyword This material can be used to define elements to act as a void, or an empty space.
      - /MAT/LAW1 (ELAST)
        Block Format Keyword This keyword defines an isotropic, linear elastic material using Hooke's law. This law represents a linear relationship between stress and strain. It is available for truss, beam (type 3 only), shell and solid elements.
      - /MAT/LAW71
        Block Format Keyword This law describes the behavior of superelastic materials. It allows modeling the behavior of the shape memory alloys (such as Nitinol).
      - /MAT/LAW75 (POROUS)
        Block Format Keyword Describes the P- $α$ porous material model. This material describes ductile Porous material with Herrmann model. It only works with 8-node brick element and is not compatible with ALE.
      - /MAT/LAW108 (SPR_GENE)
        Block Format Keyword This spring material works with six independent modes of deformation and accounts for nonlinear stiffness, damping and different unloading.
      - /MAT/LAW113 (SPR_BEAM)
        Block Format Keyword This beam type spring material works as a beam element with six independent modes of deformation. This spring accounts for nonlinear stiffness, damping and different unloading.
      - /MAT/GAS
        Block Format Keyword Describes the gas molecular weight and specific heat coefficients.
      - /MAT/USERij
        Block Format Keyword This law describes the user material.
    - 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.

View All Altair HyperWorks Help

/MAT/LAW0 (VOID)

Block Format Keyword This material can be used to define elements to act as a void, or an empty space.

Format


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/MAT/LAW0/`mat_ID`/`unit_ID` or /MAT/VOID/`mat_ID`/`unit_ID`
`mat_title`

Optional


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
$ρ$		`E`		$υ$

Definition


Field	Contents	SI Unit Example
`mat_ID`	Material identifier (Integer, maximum 10 digits)
`unit_ID`	Unit identifier (Integer, maximum 10 digits)
`mat_title`	Material title (Character, maximum 100 characters)
$ρ$	Initial density (Real)	$[\frac{kg}{m^{3}}]$
`E`	Young's modulus (Real)	$[Pa]$
$υ$	Poisson's ratio (Real)

Example (Steel)

#RADIOSS STARTER
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/UNIT/1
unit for mat
                  Mg                  mm                   s
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#-  2. MATERIALS:
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
/MAT/VOID/1/1
Void
#                RHO                   E                  Nu
             7.85E-9              210000                 0.3
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|
#ENDDATA
/END
#---1----|----2----|----3----|----4----|----5----|----6----|----7----|----8----|----9----|---10----|

Comments

Only law, mat_ID, and mat_title are used (refer to the keyword Materials).
This additional data allows defining contact interfaces with void material and property: all kinds of input for interfaces will then be available (I_gap =1, Stfac as a stiffness factor).
Contact stiffness will be correctly calculated only when E, $υ$ and t (thickness in property) are given.
When density of the void material is defined, the mass of the material is accounted in kinetic energy calculation.