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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.
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.
Hertz Formulation
Block Format Keyword The formulation is similar to a penalty formulation; but with a physical penalty stiffness based on Hertz contact theory.

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.
    - Kinematic Constraint
      Block Format Keyword
    - Penalty Method
      Block Format Keyword Penalty method is one of the contact treatments used in Radioss. Interfaces using the penalty method are based on main/secondary treatment. Penalty methods do not ensure kinematic contact continuity, but they add springs at the contact spots.
    - Lagrange Multiplier Method
      Block Format Keyword Lagrange Multiplier Method is one of the contact treatments used in Radioss and is purely mathematical and does not require physical elements (springs) to model contact. The Lagrange multiplier matrix has to be reversed at each cycle of computation and; therefore, takes more CPU time during computation, but there is no time step collapse, due to high interface stiffness.
    - Automatic Penalty Lagrange
      Block Format Keyword Same behavior as interface TYPE7 with possible switch to Lagrange multiplier formulation; if minimum constant time step (defined with /DT/INTER/CST) is reached.
    - Hertz Formulation
      Block Format Keyword The formulation is similar to a penalty formulation; but with a physical penalty stiffness based on Hertz contact theory.
      - /INTER/HERTZ/TYPE17
        Block Format Keyword This interface simulates impact between external surfaces of two brick groups. The external surfaces can only be 16-node thick shell (/SHEL16) elements.
    - ALE Interfaces
      Block Format Keyword
  - Materials
  - 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.

Hertz Formulation

Block Format Keyword The formulation is similar to a penalty formulation; but with a physical penalty stiffness based on Hertz contact theory.

Table 1. Interface Type with Hertz Formulation
Contact Treatment		Types	Application	Description
Hertz Formulation	Slide / Void	/INTER/HERTZ/TYPE17	Meshes with 16-node thick-shell or 20 bricks	Using Hertz contact theory to describe impact between external surface of two brick groups.