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Reference Guide
This manual provides a detailed list of all the input keywords and options available in Radioss.
LS-DYNA Input
This manual provides a list of LS-DYNA input files available in Radioss.
*DEFINE
*DEFINE_SD_ORIENTATION
LS-DYNA Input Interface KeywordDefines stiffness direction of discrete springs.

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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.
- 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.
  - *AIRBAG
  - *BOUNDARY
  - *CONSTRAINED
  - *CONTACT
  - *CONTROL
  - *DAMPING
  - *DATABASE
  - *DEFINE
    - *DEFINE_BOX
      LS-DYNA Input Interface KeywordDefine a rectangular box in the global or local coordinate system.
    - *DEFINE_COORDINATE_NODES
      LS-DYNA Input Interface KeywordDefines a nodal based moving coordinate system.
    - *DEFINE_COORDINATE_SYSTEM
      LS-DYNA Input Interface KeywordThis keyword defines a fixed coordinate system.
    - *DEFINE_COORDINATE_VECTOR
      LS-DYNA Input Interface KeywordThis keyword defines a local vector direction.
    - *DEFINE_CURVE
      LS-DYNA Input Interface KeywordDefines a function using tabulated input with offsets and scales.
    - *DEFINE_ELEMENT_DEATH
      LS-DYNA Input Interface KeywordDefine an element set to delete at a given time value.
    - *DEFINE_FRICTION
      LS-DYNA Input Interface KeywordDefine friction table between components.
    - *DEFINE_SD_ORIENTATION
      LS-DYNA Input Interface KeywordDefines stiffness direction of discrete springs.
    - *DEFINE_TABLE
      LS-DYNA Input Interface KeywordDefines a table.
    - *DEFINE_TABLE_2D
      LS-DYNA Input Interface KeywordThis keyword defines a 2D table.
    - *DEFINE_TABLE_3D
      LS-DYNA Input Interface KeywordDefines a 3D table.
    - *DEFINE_TRANSFORMATION
      LS-DYNA Input Interface KeywordDefines a node and entities transformation(s) used in *INCLUDE_TRANSFORM.
    - *DEFINE_VECTOR
      LS-DYNA Input Interface KeywordThis keyword defines a local vector direction.
    - *DEFINE_VECTOR_NODES
      LS-DYNA Input Interface KeywordDefine a local vector direction with nodes.
  - *ELEMENT
  - *EOS
  - *HOURGLASS
    LS-DYNA Input Interface KeywordDefine solid and hourglass formulation for 8-node solid elements.
  - *INCLUDE
  - *INITIAL
  - *INTEGRATION_SHELL
    LS-DYNA Input Interface KeywordDefine user-defined through the thickness integration rules for the composite shell element.
  - *KEYWORD
    LS-DYNA Input Interface KeywordThis keyword should always be the first card of the input file. Optionally used with *CONTROL_UNITS card to specify model units.
  - *LOAD
  - *MAT
  - *NODE
    LS-DYNA Input Interface KeywordDefines a node number and nodal coordinates in the global coordinate system.
  - *PART
    LS-DYNA Input Interface KeywordDefines a part, which combines material and property information.
  - *RIGIDWALL
  - *SECTION
  - *SET
- 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.

*DEFINE_SD_ORIENTATION

LS-DYNA Input Interface KeywordDefines stiffness direction of discrete springs.

Format


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
*DEFINE_SD_ORIENTATION
`VID`	`VFLAG`	`XT`	`YT`	`ZT`	`N1`	`N2`

Definition


Field	Contents	SI Unit Example
`VID`	Direction identifier. (Integer)
`VFLAG`	= 0 (Default) Coordinate input. = 2 Nodal input. (Integer)
`XT`, `YT`, `ZT`	If `VFLAG` = 0, the direction is specified by the vector `XT`, `YT`, `ZT`. (Real)	$[m]$
`N1`, `N2`	If `VFLAG` = 2, the direction specified by nodes `N1`-`N2`. (Integer)

Comments

This keyword maps to the X-axis of /SKEW/FIX or /SKEW/MOV.
The option “_TITLE” can be added to the end of this keyword. When “_TITLE” is included, an extra 80 characters long line is added after the keyword input line which allows an entity title to be defined.