Altair OptiStruct 2025 Release Notes

Highlights

  • Global-local analysis support for random response analysis
  • Curved beam or curved pipe element modeling with CBEND
  • Supersonic aeroelasticity
  • Implicit explicit chaining (beta)
  • SPL optimization
  • Electrostatic Analysis
  • Symmetry constraints for topology and free-size in MMO

New Features

Stiffness, Strength, and Stability
Enhancement to OUTPUT,MASSPROP and OUTPUT,MASSCOMP
A new moment of inertia table is printed in the .out file which prints the inertia with respect to the basic coordinate system. The preexisting table prints the inertia with respect to the center of gravity. Both tables are now labelled accordingly, and a note is added to mention that inertia is not printed in tensorial form.
Threshold for thin-shell thickness switched to 0.01
The threshold for printing WARNING # 1265 identifying thin-thickness shells is now changed from 0.001 to 0.01.
Auto contact for implicit nonlinear analysis (beta)
Auto-contact is now supported for implicit nonlinear analysis. Similar to auto-contact in explicit analysis, auto-contact for implicit analysis is activated by setting the TYPE field to AUTO. The ACTIVA continuation line is used to activate auto-contact for certain surfaces, and DEACTIVA continuation line is used to deactivate certain contact surfaces from auto-contact. The PCONT continuation line can be used to correspondingly activate contact properties for contact interfaces.
Nonlinear damping now supported in nonlinear static and nonlinear transient analysis for JOINTG
Nonlinear damping can now be defined via PROPERTY=NDAMP on the PJOINTG Bulk Data Entry. A force-velocity curve can now be applied to each degree of freedom associated with the joint to define nonlinear viscous damping.
Creep modeling now available for gasket elements
Creep behavior can now be modeled for GASKET elements using MGASK and MATVP Bulk Data Entries.
Modeling a curved beam or pipe element now supported
A curved beam element can now be modeled using the CBEND element and PBEND property Bulk Data Entries. CBEND and PBEND can be used for the following types of linear analyses: linear static analysis, normal modes analysis, frequency response analysis (direct and modal), random response analysis, and linear transient analysis (direct and modal).
Hydrostatic fluid element modeling available via MONVOL
MONVOL is now supported for implicit nonlinear large displacement analysis. MONVOL can now be used for specific use cases such as airspring modeling and modeling hydrostatic fluid elements. It is supported for 3D, axisymmetric, and plane-strain elements. The element set can be used to define a cavity fully filled with ideal gas/hydraulic fluid. Both hydraulic and pneumatic fluids can be modeled, and the cavity volume, applied pressure cavity pressure, and energy values can be output.
Mixture of axisymmetric and plane-stress elements in the same contact interface
A CONTACT/TIE interface can now contain axisymmetric elements (CQAXI, CTAXI) on one side and plane stress elements (CQPSTS, CTPSTS).
Explicit Dynamic Analysis
Implicit explicit chaining analysis (beta)
Explicit subcases can now continue from a preceding implicit subcase using the CNTNLSUB entry. This makes various applications available, for example, models where bolt pretensioning can be conducted first in the implicit subcase and subsequently the loading can be applied in the explicit subcase.
Low-density foam material modeling now supported
Low-density foam material can now be modeled by specifying LDFOAM material model in the MATHE Bulk Data Entry. The low-density foam material model is intended for highly compressible low-density foams with significant rate sensitive behavior. It requires the direct specification of uniaxial stress-strain curves at different strain rates for compressions. Optionally, uniaxial stress-strain curves at different strain rates for tensions can also be defined.
Out of plane Poisson’s ratio now available in MAT8
Out of plane Poisson’s ratio can now be defined using the NU13 and NU23 entries on the MAT8 Bulk Data Entry. Defining these parameters allows for precise internal force integration, better description of necking and better consistency with 3D orthotropic element results.
GSETID on TIE supported
The GSETID field on the TIE entry is now supported for explicit analysis. It is used to identify a subset of the secondary surface for which corresponding TIE contact is created regardless of the SRCHDIS value.
5-noded CPYRA element supported
The 5-noded CYPRA element is now supported for explicit analysis. It contains 5 integration points without hourglass control.
MPC support
Multi-point Constraints (MPCs) are now supported for explicit analysis. Multiple MPCs with the same ID are currently not supported for explicit analysis.
Shell offset support for contact in explicit analysis
Shell offset is now supported for contact interfaces in explicit analysis.
Corner and gauss stress/strain support
The following are now supported for explicit analysis:
  • Solid elements: Support both corner and gauss stress and strain results in the H3D file.
  • Shell elements: Support gauss stress and strain results in the H3D file.
Plasticity and damage behaviour of JOINTG elements
Plasticity and damage behaviour of JOINTG elements is now supported for explicit analysis. Four result items unique to plasticity and damage related analysis are available: JOINTG Plastic Displacement, Potential, Damage Index and Mode-mix ψ. These results are only available for explicit analysis in H3D format and supported for CARTROTA and CARDAN elements.
Rayleigh damping support for JOINTG SLIPRING
Rayleigh damping is now supported via PARAM,ALPHA1 and PARAM,ALPHA2 for JOINTG SLIPRING.
TSTIME field on LOADJG and MOTNJG now supported
The TSTIME field on LOADJG and MOTNJG to switch time duration for loading/motion curves between Total time (TOT) and Subcase time (SUB) is now supported for explicit analysis.
TTERM can now be based on subcase time or total time in explicit analysis
TTERM in explicit analysis can now be based on either a subcase time using TTERM(SUB) or for the total simulation using TTERM(TOT).
Hyperelastic material failure now supported in explicit analysis
Failure for hyperelastic materials for both solid and shell elements is now supported in explicit analysis. In addition, the new generic failure model can be used to introduce element deletion and define multiple failure criteria via GENE1 criterion in MATF Bulk Data Entries. The GENE1 criterion includes the following failure allowables: minimum hydrostatic pressure, maximum hydrostatic pressure, maximum principal stress, maximum von Mises stress, Tuler-Butcher criterion, maximum principal strain, maximum von Mises equivalent strain, maximum volumetric strain, and maximum shear strain.
GPSTRESS and GPSTRAIN results for explicit analysis now supported
GPSTRESS and GPSTRAIN results are now supported for explicit analysis (NLEXPL) in Hyper3D format. Corner stress along with GPSTRESS and GPSTRAIN are also now supported for second order elements like TETRA10 for explicit analysis.
Section force and moment results now supported in THIST
Time history output request (THIST) now supports force and moment results on selected sections. The desired outputs can be requested via the SECTION continuation line on the THIST Bulk Data Entry. Supported only in explicit dynamic analysis.
Main surface definition on ACTIVA/DEACTIVA when secondary surface is set to ALL
The main surface definition can now be specified on ACTIVA/DEACTIVA when secondary surface is set to ALL. With this option you can create or remove auto-contact between a single surface and the rest of the model.
Exponential decay for friction now supported
The FRICTION continuation line on PCONT Bulk Data Entry is now available to define exponential decay for friction. There are three options to define exponential decay:
  • Keyword EXPDCAY is specified on field 3 of the FRICTION continuation line, and subsequent fields define the sliding friction (MUs), kinetic friction (MUk), decay factor (Dc), and relative sliding velocity (Vrel).
  • Keyword EXPDCAY is specified on field 3 of the FRICTION continuation line, and keyword TESTDAT is specified on field 4, and test data is specified as follows in the subsequent fields: MU1, MU2, VREL2, and MU∞. This test data is used to fit the value of the decay factor Dc.
  • Keyword DEPEND is specified on field 3 of the FRICTION continuation line, and a 2-dimensional table is specified below if friction is only dependent on relative velocity (Vrel), and a higher dimensional table is specified if there are more dependencies, such as contact pressure. This higher dimensional table is internally converted to a TABLEMD entry.
Noise and Vibration
Enhanced rib-detection to automatically handle element normals for panel-based ERP output
Advanced algorithms were already available to automatically flip element normals when required for panel-based ERP output (for instance, when there are panels with intersecting ribs). The algorithm is now enhanced to handle a wider variety of situations, including when an edge is connected to more than two faces.
Multiple PEAKOUTs for same grid and DOF
Multiple PEAKOUT Bulk Data Entries with the same ID are now supported for the same grid and DOF. The results are added up during the peak identification process.
JOINTG contribution in GPFORCE for frequency response
The contribution from JOINTG is included in GPFORCE output in the .gpf file for frequency response analysis.
Viscous to structural damping conversion now supported
PARAM, VISC2MAT,<value> can now be used to convert viscous damping matrix to material damping matrix. The specified value is also used to scale the final material damping matrix. Supported only for complex eigenvalue analysis.
PARAM to switch MATPE ON or OFF now available
PARAM, MATPE is now available which can be used to switch between fluid element flags of PSOLID. PARAM, MATPE, OFF switches PSOLID fluid element flag from PORO to SMECH and vice-versa for PARAM, MATPE, ON.
Peak rate output support for random response resultant
Peak rate is now output as a part of the RESULTANT output for SECTION-based resultants of random response analysis. This is now available in addition to the previously available zero crossing rate.
PEAKOUT now supported for linear transient and steady state analyses
PEAKOUT is supported for transient and steady state analysis. PEAKOUT peak finding is supported for displacement, velocity, acceleration, pressure, and ERP. Peak results output is tested for displacement, velocity, acceleration, pressure, stress, strain, force, GPFORCE, SPCF, applied force, ESE, and ERP. It is supported for H3D, OP2, and PUNCH.
Global-local analysis supported for random response analysis
Global-local analysis (sub-modeling) is now supported for random response analysis. This is supported by mapping the base frequency response displacement, velocity, and acceleration results from the global model H3D file to the local sub-model. The global-local interface is specified via the SPCD entry with M option selected for mapping; the global model H3D file is specified using ASSIGN, H3DRES. A random response analysis subcase can be defined in the local model so that the frequency response results calculated in the local model based on the mapped global model results are used for subsequent random response calculations.
Multiple RADSND now supported using RADADD
Multiple RADSND Bulk Data Entries with different IDs can now be referenced by a RADADD Bulk Data Entry and this can be referenced by a RADSND command in a subcase. This is also supported for Optimization, wherein the individual RADSND IDs from RADSNDs included on a single RADADD Bulk Data Entry can be referenced in responses.
Sound Pressure Level (SPL) Optimization
Topology optimization is now supported for Radiated Sound Analysis (RADSND). The exterior sound pressure response can now be defined using RTYPE=FRPRES on the DRESP1 entry along with specifying the RADSND ID to which the response applies on the third field of the EXTN continuation line.
MultiPhysics
Applied pressure output from OptiStruct-AcuSolve co-simulation
Applied pressure in OptiStruct during the OptiStruct-AcuSolve co-simulation is now available using the OLOAD request.
Axisymmetric elements are supported in electrical analysis
Axisymmetric elements are supported in electro-thermal and electro-thermal-structure coupling analyses. Currently first order elements CQAXI and CTAXI elements are supported. Contact with axisymmetric elements is also supported.
Electrostatic subcase now available
A new standalone subcase for electrostatic analysis is now supported and can be defined using ANALYSIS ESTAT. ESTAT can be used for finding electric potential distribution in a dielectric material and evaluating electrostatic force on the structure. Electric potential distribution and electrostatic force can in turn be used as external loading in structural analysis.
Various types of inputs can be defined in the new subcase such as potential, nodal charge, area charge density and volume charge density. Relative permittivity, absolute permittivity and vacuum permittivity can also be defined via MAT1PT, MAT2PT and PARAM, VAPMTV respectively. VOLTAGE, ELECFLUX, ELECFIELD, GPCHARGE, OLOAD, SPCCHARGE, MPCFORCE (output request for MPC charge) and ESTATFORCE are some of the output requests available for the new subcase.
Electrostatic force output for electrostatic analysis is now supported
Electrostatic grid and resultant forces can now be requested for electrostatic analysis loadcases. These results are supported in H3D and OPTI format. In the case of an OPTI result request, results are output in ASCII formats including OptiStruct results format (.estatf and .estatresf) and CSV format (_estatf.csv and _estatresf.csv).
Supersonic aeroelasticity
Aeroelasticity is now supported for the supersonic regime using the Constant Pressure Method (CPM). This is now supported for trim, flutter, and divergence analyses.
Optimization
LGELIM supported for optimization
The constraint elimination method (RIGID=LGELIM) is now supported generally for optimization. If rigid element grids are in the design space for shape optimization, LGELIM is switched automatically to LAGRAN.
Level-set method supported with DDM
Domain Decomposition Mode (DDM) is now supported for level-set method.
New type of geometric responses now supported in structural optimization
Geometric response and geometric deformation response are now supported in structural optimization. These responses can be defined using DRESP1 Bulk Data Entries. Geometric response is a load-independent response that can be selected using RTYPE=GEORESP. These responses are functions of the grid locations specified in the ATTi fields of the DRESP1 entry. There are 19 types of geometric responses available.
Geometric deformation responses can be obtained from a linear static analysis. These responses are functions of the deformed grid locations and are selected using RTYPE=GEODEFR. The grids of interest are specified in the ATTi fields of the DRESP1 entry. There are 19 types of geometric deformation responses now available.
Multiple user-defined milling constraints now supported in topology optimization
Multiple user-defined milling constraints can now be defined through MILLU. Milling constraints can be defined in 3 ways using access angle, defining the dimensions of milling bit and head, and defining access angle using access angle and radius of the mill bit. Multiple access directions can now be defined using the MILLU Bulk Data Entry.
Shape fraction response now supported in vertex-based free-shape optimization
Shape fraction response is now supported in vertex-based free-shape optimization. It is activated using the RTYPE=SHAPFRAC option on the DRESP1 entry. The ATTI field can be used to specify DSHAPE IDs or it can be left blank in which case all DSHAPE entries are included. The ATTA field can be set to TOTAL(default), MAGNI, NORM, or blank. For the TOTAL option, the shape changes in the X, Y, and Z directions are added together. The MAGNI option uses the resultant magnitude of the shape change, and the NORM option only considers the shape change in the direction normal to the surface.
New adaptive time selection method now available in ESL
A new adaptive time step selection method is now supported in ESL and can be applied via TYPE = 3 in the ESLTIME Bulk Data Entry. The time steps are selected such that the target response curve is fitted by the piecewise linear curve spanned by the ESL-times, thereby enhancing the performance of the ESL method.
General
POWERFLOW through SECTION for transient analysis
POWERFLOW output is now available through SECTIONs defined in transient analysis. This is currently only supported for H3D output.
GPU support for FASTFR
GPU is now supported for FASTFR. Any solution for which the frequency-response part is performed using FASTFR can now be parallelized with GPUs.
On-the-fly H3D output enhancements
The following results are now added in on-the-fly H3D output:
  • CROD elements: Stress, Strain, Mechanical Strain, Thermal Strain, Plastic Strain, and Equivalent Plastic Strain
  • CBEAM elements: Stress and Strain
  • Shell layer results are now supported for on-the-fly H3D output for implicit nonlinear analysis
ESE support for JOINTG
Element Strain Energy (ESE) results are now supported for JOINTG elements in the regular and on-the-fly H3D files.
Friction for CARTESIA joint on JOINTG
The FRICTION continuation line can now be used to define friction for JOINTG type CARTESIA. It can either be defined in the tangential direction (using a single DOF) or in a tangential plane (using 2 DOFs). The tangential direction degree(s) of freedom can be defined using the TDOF field and the normal direction degree of freedom can be specified using the field NDOF in the FRICTION continuation line on the PJOINTG Bulk Data Entry. Frictional coefficient can be defined using the MU field. The tangential direction can be defined for a single component or spatially or there can be two separate directions, one for each tangent direction.
SPC force output for cyclic symmetry analysis
SPC force output is supported in cyclic symmetry for linear static and normal modes analysis in the regular H3D file. It is also supported in cyclic symmetry for implicit nonlinear analysis in the regular H3D file and the on-the-fly H3D file.
NLPCI support for NLDEBUG,NLP2NLC
NLPCI is now supported for NLDEBUG,NLP2NLC. When the model has an NLPCI sharing an ID with an NLPARM, the NLPCI entry is assigned the same ID as the internally generated NLCTRL.
ASSIGN,HFILE can refer to an H3D file for transient temperature input
In addition to the previously supported PUNCH file, the ASSIGN,HFILE entry can now refer to an H3D file to identify transient temperature input.
SORT2 support for FORCE output in OPTI format
SORT2 is now supported for FORCE output in OPTI format for linear static and nonlinear static analysis (SMDISP and LGDISP).
Random response output enhancements for HDF5
The following random response output enhancements are now available in the HDF5 format:
  • 1D element FORCE
  • DISP, VELO, ACCE
  • STRESS, STRAIN
  • Composite Ply STRESS, STRAIN
  • SPCFORCE
REPCASE support for linear solutions
REPCASE is now supported for linear analysis, such as normal modes analysis, complex eigenvalue analysis, frequency response analysis, transient response analysis, and random response analysis.
Create SET by INCLUDE functionality
The functionality to create a SET of elements for each INCLUDE file specified in the model is now supported via PARAM, SETINC,YES. These SETs are output to the H3D file. This is supported for all types of elements including rigid elements.
Results output on only the SKIN of the component
The MODEL card is now enhanced with the SKIN option to generate results only on the surface skin of the model.
DISPLACEMENT output now supported on skin of component
Enhanced DISP output via the SET Bulk Data Entry now supports SKIN as a new option to output displacements only on the exterior skin of the component.
Control number of digits printed in OPTI format
The number of digits of the results printed to the OPTI file can now be controlled via PARAM, DIGIT. The maximum limit is now 12 digits for any result requested.
Math equation support for symbolic substitution
Math equations are now supported for symbolic substitution. The equations can be defined anywhere in the input deck, and both %setrepsym and %defrepsym are supported. The equation syntax is consistent with how equations are supported for DEQATN; all the operators supported for DEQATN are also supported for symbolic substitution. However, unlike DEQATN, the arguments do not have to be explicitly provided. Equations can use other equations as arguments. The same rules of general symbolic substitution also apply to equations, such as the order/sequence of the cards and variables defined in the input deck matter, and the variables can be redefined in the model and are always evaluated based on the current value of the variables. Below is an example:
%defrepsym fac=2.0
%defrepsym dens=0.007*fac
%defrepsym mass=0.2*dens

MAT1           1210000.0        0.3     %dens%
CONM2         51      32       0%mass%            0.0     0.0     0.0
Symbolic substitution now supports TTERM
TTERM can now be defined using symbolic substitution. %defrepsym and/or %setrepsym can be used with TTERM in the control section of the input deck.
Enhanced support for PARAM, POST,-5 - grid renumbering and optional job termination
Original grid numbering can now be retained in the .k.op2 and .m.op2 files to maintain consistency between these OP2 and FEM files; this is now supported via the RENUM option in PARAM, POST when the value -5 is used. Additionally, the job can now be aborted after the .k.op2 and .m.op2 files are written by using the STOP option.
Enforced loading via RSP file now supported in transient analysis
Enforced loading via external RSP files are now supported in transient analysis. The enforced loads can be enforced displacements, velocities, and accelerations. The external load can now be specified on the TLOAD1 card by setting the TID field to EXTLOD and the corresponding TYPE field can be set to DISP, VELO, and ACCE. The ASSIGN, EXTLOD option can then be used to identify the external RSP file and the corresponding mapping CSV file and the ID of this ASSIGN, EXTLOD entry can be referenced on the EXCITEID field of the TLOAD1 entry.
Unit system specification of external data now supported in INISTRS/INIPS
The unit system of the external data can now be specified using the UNITS continuation line in INISTRS or INIPS Bulk Data Entries. In case the length unit specified in the INISTRS/INIPS Bulk Data Entries is different from the current model’s length unit, a model scaling is conducted for the external H3D model to match the length unit to the current model. In the case of model scaling, the new RELOC continuation line is mandatory along with the UNITS continuation line.
Shell layer results now available in on-the-fly H3D file
Shell layer results are now supported in on-the-fly H3D output format for implicit nonlinear analysis.
SET for TIME now supports specifying time interval and range
The SET entry, which defines the set of time points at which the incremental nonlinear output is requested, now includes THRU and BY functionalities. The time interval can be specified using BY and the range of points can be specified using THRU in the SET Bulk Data Entry.
Sortable tables in OptiStruct online help
New table sorting feature for large tables.
This feature has been implemented in:
Note:
Platform MPI support discontinued
As of OptiStruct 2025, the support for Platform MPI has been discontinued. This also implies that the dedicated OptiStruct Platform MPI executable will not be packaged in the HWSolvers installation anymore, and the “-mpi pl” run option will not be available anymore. Please use the available Intel MPI (Windows and Linux) and Open MPI (Linux only) options for MPI jobs.

Resolved Issues

  • When AMSES or Lanczos is used for fluid-structure PFPATH analysis, the fluid modal space calculation is no longer conducted twice.
  • The performance of steady-state analysis is enhanced in SMP parallelization mode.
  • A crash no longer occurs due to lack of MUMPS memory in a certain model with electro-thermal analysis.
  • There is no longer an issue with the joule heating calculation for 2nd order tetra and penta elements.
  • There is no longer an issue with stress results when PARAM,CURVSHL2,THICK is used in models with in-plane bending.
  • A programming error no longer shows up when the frequency range is specified on the EIGRL entry with PARAM,AEMESH,YES.
  • A programming error no longer shows up when MPC is present in a nonlinear cyclic symmetry model.
  • A model with MCIRON no longer fails to converge when stress is less than yield limit.
  • Linear heat transfer results, such as grid temperatures, are now correct when run in DDM mode.
  • ESE output is now active for JOINTG in on-the-fly H3D file. Additionally, ESE output is now supported for JOINTG.
  • GPFORCE output performance to the H3D file for normal modes analysis is now efficient when compared to similar output for linear static analysis for the same model. Significant speedup is now available for GPFORCE output for normal modes analysis.
  • The correct density field is now initialized for Optimization restart with milling constraint.
  • Certain Intel MKL libraries are no longer missing for Compose, and OptiStruct runs which require Compose no longer fail.
  • A powerflow optimization model containing both SECTION entries for powerflow and ERPPNL cards for ERP no longer fails.
  • Radiated sound pressure calculated based on PLOTEL from superelement is now accurate.
  • A model with Surface-to-Surface (S2S) CONSLI contact with DT=1.0 no longer has an issue detecting contact.
  • A model showing inefficient performance in CONTRES module and worse performance in DDM when compared to SMP is now fixed.
  • Correct MFLUID results are now generated when increasing the frequency range on EIGRL for Lanczos eigen-extraction.
  • A programming error no longer shows up if the PCONT entry is not referenced on auto-contact in an explicit model.