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Radioss 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.
*INITIAL
*INITIAL_STRESS_SOLID
LS-DYNA Input Interface KeywordInitializes the stress for solid elements in the global coordinate system.

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This manual provides details on the features, functionality, and simulation methods available in Altair Radioss.
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 2026
  New and modified features in Radioss.
- Starter Input
  This manual provides a list of all the model definition keywords and options available in Radioss.
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  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
  - *ELEMENT
  - *EOS
  - *HOURGLASS
    LS-DYNA Input Interface KeywordDefine solid and hourglass formulation for 8-node solid elements.
  - *INCLUDE
  - *INITIAL
    - *INITIAL_AXIAL_FORCE_BEAM
      LS-DYNA Input Interface KeywordDefines initial axial force applied to beams as function of time.
    - *INITIAL_FOAM_REFERENCE_GEOMETRY
      LS-DYNA Input Interface KeywordDefines the reference state for elements belonging to a part, using given nodal coordinates.
    - *INITIAL_STRAIN_SHELL
      LS-DYNA Input Interface KeywordInitializes the strain for shell elements in the global coordinate system.
    - *INITIAL_STRESS_SHELL_{OPTION}
      LS-DYNA Input Interface KeywordDefines the reference state for elements belonging to a part, using given nodal coordinates.
    - *INITIAL_STRESS_SOLID
      LS-DYNA Input Interface KeywordInitializes the stress for solid elements in the global coordinate system.
    - *INITIAL_VELOCITY
      LS-DYNA Input Interface KeywordDefines initial velocity of a node set.
    - *INITIAL_VELOCITY_GENERATION
      LS-DYNA Input Interface KeywordDefine both translational and rotational initial velocities.
    - *INITIAL_VELOCITY_NODE
      LS-DYNA Input Interface KeywordThis keyword defines an initial translational and rotational velocity of a node.
    - *INITIAL_VELOCITY_RIGID_BODY
      LS-DYNA Input Interface KeywordDefine initial velocity of a rigid body.
  - *INTEGRATION_SHELL
    LS-DYNA Input Interface KeywordDefine user-defined through the thickness integration rules for the composite shell element.
  - *INTERFACE_SPRINGBACK
    LS-DYNA Input Interface KeywordDescribes the variables to output in an initial state file or DYNAIN file at the end of the analysis.
  - *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
Radioss Example Guide
This manual presents examples solved using Radioss with regard to common problem types.
Radioss Verification Problems
This manual presents solved verification models.
Radioss Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding Radioss.
Radioss Theory Manual
This manual provides detailed information about the theory used in the Altair Radioss Solver.
Radioss User Subroutines
This manual describes the interface between Altair Radioss and user subroutines.

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*INITIAL_STRESS_SOLID

LS-DYNA Input Interface KeywordInitializes the stress for solid elements in the global coordinate system.

Format


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
*INITIAL_STRESS_SOLID
`EID`	`npg`		`LARGE`

For each integration point npg.

If LARGE = 0


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)
`SIGXX`	`SIGYY`	`SIGZZ`	`SIGXY`	`SIGYZ`	`SIGZX`	`EPSP`	`SIGXX`

If LARGE = 1


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
`SIGXX`		`SIGYY`		`SIGZZ`		`SIGYZ`		`SIGZX`
`SIGZX`		`EPSP`

Definition


Field	Contents	SI Unit Example
`EID`	Solid element identifier. (Integer)
`SID`	Part set identifier. (Integer)
`npg`	Number of Gauss integration points. = 1 Under integrated element. = 8 Fully-integrated element. (Integer)
`LARGE`	Format size. = 0 Regular format. = 1 Large format. (Integer)
`SIGij`	Stress value in the direction ij. (Real)	$[Pa]$
`EPSP`	Plastic strain.

Comments

This keyword maps to /INIBRI/STRS_FGLO.
For 8 integration points, the Gauss integration points are stored in the following order:
$\begin{array}{l} (- \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}), (\frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}), (\frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}), (- \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}), \\ (- \frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}), (\frac{\sqrt{3}}{3}, - \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}), (\frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}), (- \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}, \frac{\sqrt{3}}{3}) \end{array}$