Home
Radioss 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.
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.
/INTER/TYPE15
Block Format Keyword This interface is Ellipsoidal Surfaces to Elements Contact. It is a penalty contact interface without damping. This interface replaces interface TYPE14, especially if the mesh is coarser than the ellipsoid size.

Welcome
What's New
View new features for Radioss 2026.
Radioss Overview
Radioss is a leading explicit finite element solver for crash and impact simulation.
Tutorials
Discover Radioss functionality with interactive tutorials.
Radioss User Guide
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.
  - 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.
      - /FRIC_ORIENT
        Block Format Keyword Define specific directions for orthotropic contact friction for the main surface for contact interfaces TYPE7, TYPE19, TYPE24, and TYPE25.
      - /FRICTION
        Block Format Keyword Specific contact friction between groups of parts or two parts. This friction definition overwrites the friction model defined in the contact interface for the defined set of interfaces.
      - /INTER/TYPE3
        Block Format Keyword This interface is used to simulate impacts between two surfaces (with oriented segments). This interface works properly if the two surfaces are simply convex.
      - /INTER/TYPE5
        Block Format Keyword This interface is used to simulate impacts between a main surface and a list of secondary nodes.
      - /INTER/TYPE6
        Block Format Keyword This interface is used to simulate contact between two rigid bodies with tabulated input of the contact force. It works similar to interface TYPE3. Contact force between the bodies can be input as a function of maximum penetration. The interface also allows you to input a force function for unloading.
      - /INTER/TYPE7
        Block Format Keyword Interface TYPE7 is a multi-usage impact interface, modeling contact between a main surface and a group of secondary nodes. It is also possible to consider heat transfer and heat friction.
      - /INTER/TYPE8
        Block Format Keyword This interface is used to simulate drawbeads. It is mainly used in the process industry to model metal forming.
      - /INTER/TYPE10
        Block Format Keyword This interface is tied contact with void.
      - /INTER/TYPE11
        Block Format Keyword This interface simulates impact between edge to Edge or lines. A line can be a beam or truss element or a shell edge or spring elements.
      - /INTER/TYPE14
        Block Format Keyword This interface simulates impacts between a hyper-ellipsoidal rigid main surface and a list of secondary nodes. The hyper-ellipsoidal surface is treated as an analytical surface (hyper-ellipsoidal surfaces are only discretized for post-processing).
      - /INTER/TYPE15
        Block Format Keyword This interface is Ellipsoidal Surfaces to Elements Contact. It is a penalty contact interface without damping. This interface replaces interface TYPE14, especially if the mesh is coarser than the ellipsoid size.
      - /INTER/TYPE19
        Block Format Keyword This is a combination of two symmetric TYPE7 interfaces and one TYPE11 interface, with common input based on the same secondary/main surfaces. Secondary node group for interface TYPE7, as well as secondary and main line segments used by equivalent TYPE11 interface are virtually generated from these input surfaces.
      - /INTER/TYPE21
        Block Format Keyword Specific interface between a non-deformable main surface and a secondary surface designed for stamping. All nodes of the main surface must belong to the rigid body.
      - /INTER/TYPE23
        Block Format Keyword Defines a contact interface for airbag fabrics, modeling contact between a main surface and a secondary surface which are supposed to belong to an airbag.
      - /INTER/TYPE24
        Block Format Keyword TYPE24 is a general nodes-to-surface contact interface using the penalty method.
      - /INTER/TYPE25
        Block Format Keyword TYPE25 is a general nodes to surface contact interface using the penalty method. The penalty stiffness is constant and therefore the time step is not affected.
    - 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.
    - 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.
- 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
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.

View All Altair HyperWorks Help

/INTER/TYPE15

Block Format Keyword This interface is Ellipsoidal Surfaces to Elements Contact. It is a penalty contact interface without damping. This interface replaces interface TYPE14, especially if the mesh is coarser than the ellipsoid size.

The secondary surface must be a set of 3-node or 4-node segments (that is any kind of surface; except ELLIPS and MDELLIPS surfaces). The main surface must be a MADYMO hyper-ellipsoidal surface or a Radioss hyper-ellipsoidal surface, and Interface does not allow penetrations up to half the ellipsoid.

Format


(1)	(2)	(3)	(4)	(5)	(6)	(7)	(8)	(9)	(10)
/INTER/TYPE15/`inter_ID`/`unit_ID`
`inter_title`
`surf_ID`_s	`surf_ID`_m
`Stif`		`Fric`

Definition


Field	Contents	SI Unit Example
`inter_ID`	Interface identifier. (Integer, maximum 10 digits)
`unit_ID`	(Optional) Unit identifier. (Integer, maximum 10 digits)
`inter_title`	Interface title. (Character, maximum 100 characters)
`surf_ID`_s	Secondary surface identifier. (Integer)
`surf_ID`_m	Main surface identifier. (Integer)
`Stif`	Stiffness factor. No default (Real)	$[\frac{N}{m}]$
`Fric`	Friction coefficient. No default (Real)

Comments

Interface stiffness is a nonlinear increasing function of penetration. Stif is the interface stiffness when the element enters the hyper-ellipsoid (that is when penetration is zero).