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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.
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.
Boxes
Block Format Keyword
/BOX/CYLIN
Block Format Keyword Describes a cylinder box for entities selection.

Welcome
What's New
View new features for Radioss 2025.
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 2025
  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
  - 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.
    - /GRBEAM
      Block Format Keyword Beam Groups
    - /GRBRIC
      Block Format Keyword Brick Groups
    - /GRNOD
      Block Format Keyword Node Groups
    - /GRPART
      Block Format Keyword Describes the part groups.
    - /GRQUAD
      Block Format Keyword Describes the quad groups.
    - /GRSH3N
      Block Format Keyword Describes the 3 node shell groups.
    - /GRSHEL
      Block Format Keyword Describes the shell groups.
    - /GRSPRI
      Block Format Keyword Describes the spring groups.
    - /GRTRIA
      Block Format Keyword Describes a group of 3 node solid elements.
    - /GRTRUS
      Block Format Keyword Describes the truss groups.
    - /SET
      Block Format Keyword Defines a general entity set which can be referenced by other entities.
    - Boxes
      Block Format Keyword
      - /BOX/BOX
        Block Format Keyword Describes the box as a result of the combination of a predefined list of boxes.
      - /BOX/CYLIN
        Block Format Keyword Describes a cylinder box for entities selection.
      - /BOX/RECTA
        Block Format Keyword Describes a rectangle box for entities selection.
      - /BOX/SPHER
        Block Format Keyword Describes a spherical box for entities selection.
    - Lines
      Block Format Keyword
    - Surfaces
      Block Format Keyword
  - 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.
- 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.
- 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
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.

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/BOX/CYLIN

Block Format Keyword Describes a cylinder box for entities selection.

Format


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/BOX/CYLIN/`box_ID`/`unit_ID`
`box_title`
`N1`	`N2`		`Diameter`
`X`_p1		`Y`_p1		`Z`_p1
`X`_p2		`Y`_p2		`Z`_p2

Definition


Field	Contents	SI Unit Example
`box_ID`	Box identifier. (Integer, maximum 10 digits)
`unit_ID`	Unit identifier. (Integer, maximum 10 digits)
`box_title`	Box title. (Character, maximum 100 characters)
`N1`	Node identifier. (Integer, maximum 10 digits)
`N2`	Node identifier. (Integer, maximum 10 digits)
`Diameter`	Diameter of cylinder. (Real)
`X`_p1	`X` coordinate of point `P1`. (Real)
`Y`_p1	`Y` coordinate of point `P1`. (Real)
`Z`_p1	`Z` coordinate of point `P1`. (Real)
`X`_p2	`X` coordinate of point `P2`. (Real)
`Y`_p2	`Y` coordinate of point `P2`. (Real)
`Z`_p2	`Z` coordinate of point `P2`. (Real)

The pairs of nodes N1 and N2, or the pairs of points P1 and P2, are used to define the axis of the finite cylinder.

box_cyl — Figure 1.

Comments

A box (CYLIN) defined above is used for:
- a simple group definition (/GRBEAM, /GRBRIC, /GRNOD, /GRQUAD, /GRSH3N, /GRSHEL, /GRSPRI /GRTRUS, Lines, Surfaces) - all entities within the box are included
- a complex box definition (see /BOX/BOX)