Altair Radioss 2026 Release Notes

New Features

LS-DYNA Readers
  • New LS-DYNA format reading capability
    • *CONTACT_AUTOMATIC_ONE_WAY_SURFACE_TO_SURFACE
    • *DAMPING_FREQUENCY_RANGE
    • *DATABASE_NODAL_FORCE_GROUP
    • *INTERFACE_SPRINGBACK
    • *MAT_062 (VISCOUS_FOAM)
    • *MAT_163 (MODIFIED_CRUSHABLE_FOAM)
    • *PART_SENSOR
ALE and FSI options
  • /ALE/GRID/LAGRANGE: Introduces a new ALE grid formulation allowing the transition to a Lagrangian framework (grid velocity set equal to material velocity). The grid is updated using the material velocity.
  • /DFS/DETPOINT/NODE, /DFS/DETPOINT/SET: A new Fast Marching Method (Ishadow = 2) estimates detonation wave arrival time while accounting for obstacles and spatially varying velocities in the computational domain.
Materials, Equation of State and Failure Models
  • /EOS/COMPACTION_TAB: New equation of state to model tabulated compaction behavior for granular materials, using user-defined functions.
  • /FAIL/COMPOSITE: Simple failure model for composite materials, applicable to composite fabric lamina defined in the 1-2 plane.
  • /FAIL/LEMAITRE: New continuum damage mechanics (CDM) failure model based on Lemaitre’s theoretical approach.
  • /MAT/LAW127 (ENHANCED_COMPOSITE): New composite materials with multiple criteria (fiber/matrix tension and compression, shear), interactive failure envelopes and progressive stiffness reduction with smooth damage variables, allowing stable post-failure response.
  • /MAT/LAW133 (GRANULAR): New material model for dry granular media (for example, sand), using a pressure-dependent elastic-plastic formulation. Together with /EOS/COMPACTION_TAB it allows to define so-called Sjöbo Dry Sand model.
  • /MAT/LAW134 (VISCOUS_FOAM): New material model for open-cell urethane foam, typically used in the ribs of Euro-SID side impact dummies.
  • /MAT/LAW163 (CRUSHABLE_FOAM): New crushable foam material model including strain rate effects. Typically used for modeling low-density, closed-cell polyurethane foams.
Loadcases
  • /DAMP/FUNCT: New mass damping option allowing the damping value to be scaled as a function of time, using a user-defined curve.
  • /LOAD/PBLAST:
    • New warning message issued when the table-defined impulse is too large to generate a physical wave.
    • New Exp_data flag to activate an updated formulation for ground reflection, assuming hemispherical wave propagation.
Engine File
  • /DEL/PART, /DEL/PART/1: New option to delete a part list directly from the Engine file.

Enhancements

LS-DYNA Reader
  • *PART_COMPOSITE: Improvement of the card reading for specific input case.
  • *BOUNDARY_PRESCRIBED_MOTION: New capability to read the SET_BOX option.
  • *CONTROL_TIMESTEP: Time step scale TSSFAC is now always read, not just for nodal time steps.
  • *DATABASE_BINARY_D3PLOT: Spring forces are now output by default (/ANIM/SPRING/FORC).
  • *DATABASE_NODOUT: Rotational velocity and rotational acceleration are now included in the time history output.
  • *HOURGLASS, *CONTROL_HOURGLASS: Improvements to the mapping of hourglass modes to the Radioss solid formulation.
  • *INITIAL_VELOCITY_GENERATION: Improved reading of local coordinates.
  • *MAT_054 (ENHANCED_COMPOSITE_DAMAGE): This material is now mapped to /MAT/LAW127 instead of /MAT/LAW25.
  • *MAT_057 (LOW_DENSITY_FOAM): Improved reading and mapping of damping parameters.
  • *MAT_081 (PLASTICITY_WITH_DAMAGE): Fixed reading issue for the default values of FAIL and EPS_max.
  • *MAT_083 (FU_CHANG_FOAM): Improved reading and mapping of damping parameters.
  • *MAT_105 (DAMAGE_2): Failure parameters are now read and mapped to /FAIL/LEMAITRE.
  • *MAT_224 (TABULATED_JOHNSON_COOK): Improved reading and mapping of failure parameters.
  • *MAT_169 (ARUP_ADHESIVE): Parameters SHT_SL and SHRP are now read and mapped to /MAT/LAW169.
Materials, Equation of State and Failure Models
  • /EOS/GRUNEISEN: New initial energy calculation for the case when gamma = 0.
  • /FAIL/FLD: New output for incremental strain ratio Beta in /H3D/SHELL/FAILURE/ID=<>/MODE=3.
  • /FAIL/USERi: The damage output variable DFMAX is now available in the user-defined failure model.
  • /MAT/LAW2 (PLAS_JOHNS): Thermal dependency can now be activated even if strain rate dependency is not defined.
  • /MAT/LAW51 (MULTIMAT):
    • Improved temperature calculation in the multi-material solver.
    • /MAT/LAW133 (GRANULAR) material can now be used in the multi-material model (Iform = 12).
  • /MAT/LAW87 (BARLAT2000): New Starter checks and modifications to parameters alpha2 and alpha6 to avoid concave yield surface shapes.
  • /MAT/LAW90: New optional parameters for elastic modulus in contact (Econt) and tensile cutoff stress (Tcut).
  • /MAT/LAW108 (SPR_GENE): The mass of the node attached to the spring elements is now used to define spring mass in case of zero-length springs and Imass = 1 from spring property (/PROP/TYPE23).
  • /MAT/LAW108 (SPR_GENE), /MAT/LAW113 (SPR_BEAM): New flag H = 9 to model nonlinear elastic-plastic behavior with kinematic hardening.
  • /MAT/LAW151 (MULTIFLUID):
    • Temperature is now output for multi-fluid materials.
    • JWL material burning models (/MAT/LAW5) are now compatible with multi-fluid materials.
Element and Properties
  • /PROP/TYPE1 (SHELL): Corrected internal energy update for 3-node shell elements (/SH3N) with Ish3n = 30 after element deletion.
  • /PROP/TYPE34 (SPH): New option h_1D = 3 to compute smoothing length from the maximum initial inter-particle distance with 3D bounded expansion.
  • /PROP/TYPE23 (SPR_MAT), /PROP/TYPE13 (SPR_BEAM): Corrected spring behavior when the 3rd node of the spring and the local coordinate system are not defined.
  • /PROP/TYPE45 (KJOINT2): Increased tolerance for the initial check of the local coordinate system.
  • /RBE3: New flag Iform to switch to a penalty formulation or to automatically switch when incompatible kinematic conditions are detected.
  • /SLIPRING/SHELL: Improved initial checks for single precision versions.
Loadcases
  • /FUNCT_PYTHON:
    • Python functions can now be used in monitored volumes and injectors. Variables like airbag pressure, area, temperature, and volume can be used within Python functions.
    • The ACTIVE_NODE option can now be used to define specific values for each node in a node set.
    • /INIBRI: Solid formulation Isolid = 5 is now compatible with initial states.
  • /PRELOAD:
    • Negative force or stress can now be defined for preloading.
    • New option to define loading based on curves using /FUNCT or /FUNCT_SMOOTH, helping to reduce dynamic behavior and create smoother loadings.
  • /SECT: Reduced memory usage for section force initialization in the Starter.
  • /SPH/RESERVE: New Starter error message if the number of particles in the model is zero.
  • /TABLE/1: Improved Starter check for the combination list of scale factors in multi-dimensional tables.
Contact Interfaces
  • /INTER/TYPE1:
    • Improved ALE tied contact for axisymmetric or plane strain 2D analyses.
    • Automatic correction of tied contact for duplicated segments on both ALE and Lagrangian sides.
  • /INTER/SUB: Edge-to-edge treatment forces for contact interface /INTER/TYPE24 (Iedge = 1) are now included in the sub-interface force output.
  • /INTER/TYPE21: The /FRICTION model can now be used with the stamping contact interface.
  • /INTER/TYPE25:
    • New option Igap = 5 to define a constant gap value.
    • Improved edge-to-edge treatment.
Animation and Time History
  • New nodal output for external pressure PEXT in animation files (/ANIM/NODA/PEXT, /H3D/ELEM/PEXT) and time history files (/TH/NODE).
  • Element temperature (/ANIM/SHELL/TEMP, /H3D/SHELL/TEMP) is now output for shell elements, providing the material is compatible with thermal analysis.
  • Strain rate is now output in animation files for 2D analyses (where strain rate is computed for the material).
  • /H3D/SHELL/DAMG, /H3D/SHELL/FAILURE:
    • Improved writing times when all damage or failure modes (MODE=ALL) are requested for each ply or model.
    • Variable name simplification to ease post-processing.
  • /H3D/SHELL/FAILURE: New option to select the integration point using MEMB; NPT=UPPER or NPT=LOWER.
  • New output for plastic work (WPLA) as a global variable in time history files (/TFILE), as well as plastic work per part (PW) and per subset (/TH/SUBS).
Starter and Engine
  • ARM version is now compiled using latest version of ArmFlang Compiler + Red Hat Enterprise Linux 8.
  • Intel version is now compiled using OneAPI 2025.1 IFX compiler.

Resolved Issues

LS-DYNA Reader
  • *AIRBAG_SIMPLE_AIRBAG_MODEL: Set ID is not updated correctly when *SET_ID is renumbered internally.
  • *BOUNDARY_PRESCRIBED_MOTION_RIGID: Fixed reading issue when the direction is defined in the vector VID.
  • *CONTACT_AUTOMATIC: Corrected conversion for IPSTF and Iedge when SOFT = 2.
  • *DEFINE_COORDINATE_NODES: Fixed reading issue where the local coordinate system was not correctly defined for specific models.
  • *LOAD_RIGID_BODY: Fixed error message issue.
  • *LOAD_SEGMENT: Fscaley scale factor is correctly mapped to Radioss.
  • *MAT_034 (FABRIC):
    • Improved reading for FORM = 14 (no shear curve, G = 0).
    • Fixed reading issue for FORM = 14 with no load curves.
    • Improved mapping of ELFORM element formulations.
  • Corrected reading for the number of integration points through the thickness.
  • *MAT_105 (DAMAGE_2):
    • Fixed reading issue when the first plastic strain value is non-zero.
    • Improved handling of yield curves defined with EPSi and ESi when EPS1 > 0.
  • *MAT_S01 to *MAT_S08: Default mass of 1E-12 times the length is added to spring elements.
  • *PARAMETER: Fixed reading issue when a negative sign is used with parameters.
  • *SECTION_SHELL: Fixed reading issue when successive sections in the same keyword have ICOMP = 1.
Materials, Equation of State and Failure Models
  • /EOS/TILLOTSON: Corrected compatibility with the multi-fluid material /MAT/LAW151.
  • /FAIL/COCKCROFT: Fixed failure model behavior when used with foam material /MAT/LAW70.
  • /HEAT/MAT: Corrected thermal behavior with /MAT/LAW2.
  • /MAT/LAW24 (CONC): Strain tensor values were previously twice as large since version 2022.3.
  • /MAT/LAW25 (COMPSH): Fixed memory allocation issue for specific models.
  • /MAT/LAW34 (BOLTZMAN): Improved material behavior with Isolid = 5.
  • /MAT/LAW58 (FABR_A): Corrected stability issue for QEPH shell elements (Ishell = 24) with reference metric, multiple integration points through the thickness, and specific fabric materials.
  • /MAT/LAW66: Improved material behavior for shear and volumetric compression.
  • /MAT/LAW70 (FOAM_TAB): Initial elastic modulus was not correctly set when the value was null (or empty).
  • /MAT/LAW90: Corrected reporting of curve scale factor and offset when curves are duplicated.
  • /MAT/LAW102 (DPRAG2): Fixed issue with Pmin (minimum pressure) behavior.
  • /MAT/LAW114 (SPR_SEATBELT): Fixed time step issue for specific models.
  • /MAT/LAW119 (SH_SEATBELT): Some virtual springs were duplicated in specific models
Element and Properties
  • /PROP/TYPE11 (SH_SAND): Fixed tensor strain output issue when Ipos = 1 for shell bending.
  • /PROP/TYPE14 (SOLID): Fixed parallel arithmetic issue for specific models with hyper-elastic material, quadratic tetrahedra (Itetra10 = 2), and element distortion control (Icontrol = 1).
  • /PROP/TYPE17 (STACK): Fixed memory allocation issue for Plyxfem > 0.
  • /SHELL and /SH3N: Improved stack, plies, and layers thickness update when thickness is defined in the shell element.
Contact Interfaces
  • /INTER/TYPE2: Improved tied behavior for solid elements with surface-to-surface input.
  • /INTER/TYPE7: Fixed memory allocation issue using MPI and for specific models.
  • /INTER/TYPE24: Improved behavior with INACTI = -1 and INACTI = -2 for specific models.
  • /INTER/TYPE25: Enhanced contact interface behavior when solid elements are deleted, with improved contact surface updates.
  • /PROP/TYPE23 (SPR_MAT): Spring length is not considered with Imass = 1 and /MAT/LAW108.
  • /PROP/TYPE51: Fixed tensor strain output issue when Ipos = 1 for shell bending.
Loadcases
  • /ADMESH: Fixed memory allocation issue for specific models.
  • /ALE/MAT, /EULER/MAT: Fixed communication issue for ALE or Euler material formulations with MPI version, and specific models with degenerated brick elements.
  • /BEM/DAA: Fixed computation time issue.
  • /INISPRI: Fixed memory allocation issue with initial spring setting for specific models.
  • /INISTA/BRICK: Initial state was not correctly recovered for /TETRA4 elements and /MAT/LAW1.
  • /INITEMP: Fixed temperature initialization issue for specific models.
  • /LOAD/PBLAST: Engine behavior with SMP version for specific models.
  • /PRELOAD/AXIAL: Corrected Starter error message when using spring /PROP/TYPE23.
  • /RETRACTOR/SPRING: Improved mass computation when the Elem_size parameter is larger than the mesh size.
  • /SUBDOMAIN:
    • The flag Iale in the solid property (/PROP/TYPE14) is now correctly considered.
    • Fixed multi-domain issues in models including composites and added mass.
Animation and Time History
  • /ANIM/BEAM/FORC, /H3D/BEAM/FORC: The moments for node 1 and node 2 were swapped
  • /ANIM/SHELL/IDPLY/..., /H3D/SHELL/.../PLY=...: Fixed issue where unexpected plies were added in animation files when /DRAPE was used with a few elements or composite parts.
  • /H3D/ELEM/TDET: Fixed missing detonation time output for /TRIA elements.
  • /H3D/SHELL: Memory allocation issue for specific models and outputs.
  • /H3D/SHELL/DAMG/ID=<mat_ID>/MODE=ALL/PLY=ALL/NPT=ALL: Memory allocation issue for Radioss Engine.
  • /H3D/SOLID/ORTHD: Memory allocation issue when composite thick-shell is defined with fewer than 10 layers in one stack and more than 10 layers in another.
  • /TH/INTER: Fixed contact area (CAREA) output for sub-contacts (/INTER/SUB) in specific models.
Engine File
  • /DAMP: Fixed reading issue when ID has more than 5 digits.
  • /DEL/SHELL, /DEL/SH_3N: Fixed issue where some listed elements were not removed from specific models.
  • /SET: Fixed reading issue when comments are present in the Engine file(s).