What's New

View new features for OptiStruct 2025.1.

Altair OptiStruct 2025.1 Release Notes

Highlights

Second order shells for large displacement nonlinear analysis
Fast contact (FASTCONT) enhancements (S2S and friction support)
SENSOR Enhancements (PAFLUID and pretension force support)
Resonant frequency response for optimization
Optimization support for piezoelectric analysis
Convection topology optimization
Milling constraints with no hole constraints
Sound Pressure Level (SPL) response with shape and topography optimization
Viscoelasticity with shell element support

New Features

Stiffness, Strength, and Stability

Second order shell elements in nonlinear large displacement analysis: Second order shell elements are now supported in large displacement nonlinear static analysis (LGDISP).

PJOINTG now includes NDAMP with velocity and displacement dependency: PJOINTG now includes nonlinear damping with velocity and displacement dependency. A force-velocity-displacement curve can now be defined for nonlinear damping using the NDAMP continuation line. The force, velocity, and displacement values to define the curve can be specified in the Fi, vi, and ui fields and the curve is applied to each degree of freedom associated with the joint, listed in the FDOF, VDOF and UDOF fields. NDAMP is currently only supported for CARTESIA joint.
Multiple enhancements in JOINTG: Multiple enhancements are now available when defining ELAS, DAMP and NDAMP properties. Off-diagonal terms of the stiffness matrix can now be defined for PROPERTY = ELAS and DAMP. An additional ELAS or DAMP definition with additional DOF defined specifies coupling between two different degrees of freedom of the stiffness matrix. For example, when two ELAS definitions are specified, the first ELAS definition defines the diagonal terms of the stiffness matrix, that is, stiffnesses along the same degree of freedom. The second ELAS definition defines the off-diagonal terms of the stiffness matrix, that is, the coupling stiffnesses between two different degrees of freedom. For PROPERTY = NELA, two DOFs can be specified where the second DOF specification defines a nonlinear force at DOF 1 as a function of the displacement at DOF 1 plus a nonlinear force at DOF 1 as a function of joint displacement at DOF2.
Anisotropic and orthotropic thermal expansion definition now supported for MAT1 + MATS1/MATVE/MATVP: Orthotropic and anisotropic coefficients of thermal expansions can be defined for solid elements for implicit small displacement and large displacement analyses. This definition is available for MAT1 combined with all material Bulk Data Entries that share the same material ID with MAT1 (for example, MATS1, MATVE, MATVP, and so on).
Strain rate dependent plasticity now available for shell elements: Strain rate dependent plasticity is now supported for shell elements in both small and large displacement analysis. Additionally, plane stress elements in nonlinear static and nonlinear transient small displacement analyses are also supported. When rate dependent plasticity is defined, plastic strain rate results can be requested via the STRAIN I/O Option and Subcase Information Entry. Plastic strain rate results are now supported for both solid and shell elements in H3D and on-the-fly H3D. Shell layer results now also include plastic strain rate when RATE and NDIV options are specified. Valid for implicit analysis only.
Output stresses for plane stress, plane strain, and axisymmetric elements are now provided in the material co-ordinate system by default: For plane stress elements (CQPSTS and CTPSTS), by default, the requested stress and strain results are now provided in H3D format, in the material coordinate system with the type of stress/strain set to DIRECT. However, when PARAM, OPSTS, OLD is defined, the requested stress and strain results are provided in the elemental coordinate system with result type set to TENSOR unless you manually requests a DIRECT type of stress/strain result. For plane strain and axisymmetric elements (CQPSTN, CTPSTN, CQAXI, CTAXI, CQAXIG and CTAXIG), stress and strain results are always provided in the material system by default.
Bernoulli beam is assumed when shear modulus is not specified in MAT1: Bernoulli beam is assumed when either shear modulus and Poisson's ratio are both unspecified or when shear modulus is specified as 0.0 explicitly, regardless of Poisson's ratio. This is applicable for linear and nonlinear implicit analysis and only beam elements.
Inertia relief analysis with preloaded LGDISP nonlinear analysis: Inertia relief is now available in large displacement preloaded static subcase, wherein inertia relief support is now enhanced based on the deformed mesh from the LGDISP preloading subcase. This results in a good balance in the preloaded linear subcase.

Explicit Dynamic Analysis

PBUSHT now includes unloading

Unloading behavior can now be modelled in PBUSHT using the KUN field. You can define six fields which reference unloading force versus deflection tables for DOFs 1 through 6, respectively. This is available only for explicit analysis.

Shell elements are now supported in viscoelastic materials

Material properties for nonlinear viscoelastic materials can now be defined for shell elements via MATVE and MATTVE Bulk Data Entries. Valid for both implicit and explicit analysis.

Plasticity can now be defined using the PLASTIC Bulk Data Entry

The new PLASTIC Bulk Data Entry can be used to describe elastoplastic material behavior (currently supported for MAT1). PLASTIC offers the ability to create a specific assembly of constitutive equations choosing a custom-made combination of HILL yield criterion, hardening rule, and/or strain rate dependency. For example, PLASTIC can be used in special scenarios where the material has an isotropic elastic behavior with an orthotropic elasto-plasticity using (for example) a HILL yield criterion, a tabulated work hardening rule, and a nonlinear strain rate dependency rule. This option is available for solid and shell elements in explicit analysis and only solid elements in implicit analysis.

PCOMPLS enhancement – stack direction specification based on material or element coordinate system

The composite material ply thickness direction or stack direction can now be specified using the elemental or material coordinate system via STACKD, DIR or CORDM options in the PCOMPLS Bulk Data Entry. When the DIR option is specified on the STACKD continuation line, the stack direction is determined as parametric direction of HEXA elements. When CORDM option is specified, the stack direction is determined by the material coordinate axis 1/2/3. The parametric direction with the smallest angle with the specified axis is used as stack direction. This feature is valid for both implicit and explicit analysis.

Section forces are now written in THIST hdf5 file for pretension bolt results for explicit analysis

For a nonlinear explicit analysis subcase with a pretension bolt setup, the section forces of pretension bolts are now printed to THIST hdf5 file. The THIST Subcase Information Entry must be present in the subcase along with the THIST Bulk Data Entry defined in the input deck. The FREQ field must be defined in the THIST Bulk Data Entry. Valid for explicit analysis only.

New cross-section support for integrated beam

The following new cross-section support is now available for integrated beam:

I-section for Nonlinear Implicit analysis
I-section for Explicit dynamic analysis (Beta release)
L-section for Nonlinear Implicit analysis (Beta release)

Plasticity can now be defined for composite material via PCOMP and MATS1

Plasticity can now be defined for PCOMP via MATS1. Valid for both nonlinear implicit and explicit analysis for the PCOMP card.

Performance enhancement for contact in explicit analysis

Significant performance enhancements in the contact solution are implemented for some models in explicit analysis. This can significantly reduce the total solution time in large models.

Noise and Vibration

Strain energy proportional damping can now be defined for normal modes analysis: In MAT1, the ESDAMP continuation line can be used to define the material damping for strain energy proportional damping calculation. OUTPUT, ESDAMP can be used to request the strain energy proportional damping output in the .esdamp file. If The ESD value is not defined, the material is not included in the calculation of the strain energy proportional damping.
MULTIPLEOUTPUT support for STEADY: MULTIPLEOUTPUT is now supported for steady state analysis (ANALYSIS = STEADY). That is, for the same output, multiple requests can be specified with different options, such as SET IDs, result types (such as VON, DIRECT), and so on. This feature can be activated using SYSSETTING(MULTIPLEOUTPUT=YES).
Residual vectors are now included in normal modes analysis with Lanczos method: The residual vectors defined using RVDOF or USET are now included in the modal domain in normal modes analysis solved using Lanczos method.
SMDISP and LGDISP preloaded normal modes and frequency response analysis now support auto-contact: Normal modes analysis and frequency response analysis preloaded with small displacement or large displacement analysis can now be defined with auto-contact.
RESVECs are included by default in modal complex eigenvalue analysis with Lanczos: For modal complex eigenvalue analysis with the Lanczos eigensolver, the case control command RESVEC is now set to YES by default.
USET can now be defined on fluid dof for RESVEC generation with AMSES: USET can now be defined on fluid DOF for RESVEC generation with AMSES.

Optimization

Resonance frequency available as a response in DRESP1

The frequency at which certain peaks or valleys (anti-peaks) of nodal displacements, accelerations, velocities, and acoustic pressure occur in a frequency response analysis can be selected as a response. These frequencies correspond to the extreme values of nodal displacements, velocities, accelerations (both translational and rotational), and acoustic pressure that occur within the frequency range, that is, the frequencies at which resonance occurs. There are four options available: the frequency of the highest peak (FQ-HPK), the frequency of the first peak (FQ-FPK), the frequency of the lowest anti-peak (FQ-LAN), and the frequency of the first anti-peak (FQ-FAN). Resonance frequencies are measured in hertz.

SPL response in shape optimization

SPL can now be defined as a response in shape optimization. Acoustic pressure (SPL) output from radiated sound analysis (via the RADSND card) can be defined as a response via DRESP1 and RTYPE = FRPRES in topography optimization and free shape optimization.

Convection boundary dynamically updated during topology optimization

Convection boundary is now dynamically updated during the topology optimization process. With this capability, new convection boundaries are added on the newly generated surfaces from topology design. This is currently supported for implicit linear steady state heat transfer analysis for solid elements (TETRA, TET10, HEXA, HEXA20, PENTA, PEN15, PYRA, PYRA13).

FASTCONT enhancement for optimization

FASTCONT now uses the converged contact status from the previous iteration in optimization, thereby significantly reducing the number of contact iterations required in the later design iterations resulting in drastically reduced overall runtime of the solution.

Optimization for piezoelectric analysis

Topology optimization (SIMP and levelset), shape optimization and size optimization (of non-piezoelectric region) are now supported for piezoelectric analysis. The following response types can be defined in topology, shape and size design variables.

Linear static analysis: DISP, COMP (total and regional)
Normal modes analysis: FREQ, DISP (mode shape)
Direct and modal frequency response: FRDISP, FRVELO, FRACCL

Only valid for implicit analysis.

Vertex-based free shape optimization with MMO

Vertex-based free shape optimization is now supported with MMO (only supported for matching meshes).

Note: Classic free-shape optimization was already supported with MMO.

MILLU can now be defined with NOHOLE

MILLU continuation line in the DTPL Bulk Data Entry can be used to define various milling tools and multiple milling directions. NOHOLE can now be additionally defined in the MILLU continuation line to prevent the formation of through-holes in the draw direction. While multiple access directions can be defined using the MILLU Bulk Data Entry, NOHOLE can be defined in a single direction only.

Level set optimization can now be combined with other optimization types

Level set optimization now supports simultaneous topology, size, or shape optimization, that is, combination of topology with size and shape optimization is supported.

Projected geometric response now available to be defined via DRESP1

A new response can now be created for the projection of a geometry (projected geometric response) via DRESP1. It is a load independent response that can be selected using RTYPE = GEORESP. These responses are functions of the grid or element IDs specified in the ATTi fields of the DRESP1 entry. There are nine types of projected geometric responses available, and all are controlled by the ATTA field. PXAREA3, PYAREA3, PZAREA3, PXAREA4, PYAREA4, and PZAREA4 are defined by grid IDs. PXAREA, PYAREA, and PZAREA are defined by shell element IDs. All nine responses require specification of a coordinate system in DRESP1.

OPTIMOMP is now activated by default

OpenMP parallelization is now activated by default for enhanced computational efficiency while solving the optimization problem using DUAL2, MFD, or SQP algorithms. It can be turned off using DOPTPRM, OPTIMOMP, NO.

Geometric sensitivity influence can now be activated in topography or free shape optimization

Geometric sensitivity effects in topography or free shape optimization can now be activated via DOPTPRM, GEOMSENS. In the case of ERP and SPL responses, influence to the sensitivity can be large in free shape optimization and can be activated via this parameter if the run time is acceptable.

Loading frequencies introduced by RESVEC included in Lanczos method

When FREQ3/4/5 are used, loading frequencies added by RESVEC are now included in loading frequencies with Lanczos method. In optimization, these loading frequencies introduced by RESVEC are also now included in the optimization responses.

General

FASTCONT analysis now supports S2S contacts and friction: FASTCONT analysis is now also available for surface-to-surface type of CONTACTs. FASTCONT with friction is also now supported.
FASTCONT analysis prints contact switches from last non-converged iteration: When a FASTCONT analysis does not converge, a list of fast contact switches in the last iteration is printed to the output (.out) file for review. By default, the limit of number of gaps printed is 50.
SENSOR card can now be used in conjunction with CAFLUID and PAFLUID: The SENSOR Bulk Data Entry can now be used along with CAFLUID and PAFLUID, wherein the mass flow rate in the PAFLUID Bulk Data Entry can be updated based on the temperature bounds defined in SENSOR via the COND continuation line. Temperature-mass flow rate feedback mechanism is currently supported for linear and nonlinear transient heat transfer analyses.
SENSOR can now be used to terminate the run when bolt is completely loosened: SENSOR can now be used to monitor the pretension force in an analysis and terminate the solution if the value reaches a zero or a prescribed value. This feature can be implemented by defining TYPE = FORCE and STYPE = PRETENS followed by PRETENS ID on the SENSOR Bulk Data Entry. The force value can be specified using the UBOUND entry on the COND continuation line, the model can be terminated based on this UBOUND value using an ACTION continuation line. This helps to cut the solution time down significantly and terminate the run when a bolt pretension force is close to 0, that is, when thread contact is completely open.
Start time, end time, and ramp can now be defined for external RSP load file, plus further enhancements: The mapping (.csv) file for the external load file (.rsp) can now include additional columns to define start time, end time, and ramp. Starting time, ending time ramp, and ramp can be specified to extract a slice of the RSP data. The first column of the mapping file can also be used to define channel ID, but this data is not used by OptiStruct. The external load (.rsp) and mapping (.csv) files no longer need to be sharing the same file name. A new column can be added in the mapping file to define the coordinate system. Valid for implicit linear transient analysis only.
OptiStruct checkrun can be stopped after .cpr file creation: The Optistruct check run can be stopped after the initial contact conditions file (.cpr file) has been created via CONTPRM, PREPRT. This helps in reducing the overall solution time by reducing redundant checkruns, for example, in HyperMesh or SimLab.
GPFORCE results are now available for linear static analysis preloaded with an LGDISP analysis: GPFORCE results are now available in H3D and OPTI formats (.gpf) for linear static analysis preloaded with a large displacement analysis.
Section forces and moments now available in HDF5 format: Section resultant forces and moments are supported for in HDF5 result format for linear and nonlinear static, linear transient, frequency response, and random response analysis types. This output can be requested via the RESULTANT I/O Option or Subcase Information Entry.
On-the-fly results for CELAS1 and CELAS2 now supported: On-the-fly axial stress results for CELAS1 and CELAS2 elements are supported via the STRESS I/O Option or Subcase Information Entry in TENSOR and DIRECT formats.
ESE and EKE are now supported in LGDISP preloaded normal modes and FRF analysis: Element strain energy and element kinetic energy can now be requested for normal modes analysis and frequency response analysis preloaded with nonlinear large displacement analysis.
ELFORCE result now supported on-the-fly for 1D and shell elements: ELFORCE on-the-fly H3D results are now supported for 1D elements namely, ROD (CROD), BAR (CBAR, CBEAM), BUSH (CBUSH), CELAS1, CELAS2, SCALAR DAMPER (CDAMP1, CDAMP2), and VISCOUS DAMPER (CVISC) elements. ELFORCE results are now supported on-the-fly for CQUAD4, CTRIA3, CQUAD8, and CTRIA6 shell elements. By default, the result type for on-the-fly H3D is TENSOR. DIRECT option is also available and it must be explicitly specified if direct force output is required.
SPCFORCE is now supported for LGDISP preloaded FRF analysis: SPCFORCE result is now supported for frequency response analysis preloaded with nonlinear large displacement analysis.
On-the-fly results are now supported for composite ply results: Composite ply stress and strain (CSTRESS and CSTRAIN) results can now be requested on-the-fly for random response analysis which results in significant reduction of disk space requirements. On-the-fly PSD computations are automatically activated as long as the underlying frequency response results are not needed. Additionally, on-the-fly RMS computations are automatically activated as long as the PSD results are not needed. Valid for implicit analysis only.
ELFORCE results (regular and on-the-fly) are now supported for shell elements in random response analysis: ELFORCE results for regular H3D and on-the-fly H3D are now supported for shell elements in random response analysis. On-the-fly computations are supported when the underlying FRF plate forces are not needed for output, which results in significant reduction of disk space requirements. Valid for implicit analysis only.
Composite ply results now available on-the-fly: Composite ply results, namely CSTRESS, CSTRAIN, and CFAILURE are now available in on-the-fly H3D format. These results are supported only for implicit nonlinear static nonlinear transient, both small displacement and large displacement analysis.
PARAM, OP2GM34 can now be activated using SYSSETTING or by modifying the optistruct.cfg file: PARAM,OP2GM34 can now be activated using SYSSETTING(OP2GM34 = YES or NO) or by modifying the optistruct.cfg file. The OP2GM34 controls the output of GEOM3 and GEOM4 data blocks to the OP2 file when PARAM, POST, -1 is specified. In the optistruct.cfg file, the line OP2GM34 = TRUE/FALSE can be uncommented for the desired output. The default is TRUE.
Elemental temperatures can now be read from PolyFoam .h3d files and can be mapped to the current grid: The TEMPT Bulk Data Entry in combination with TEMP Subcase Information Entry can now be used for reading elemental temperatures from PolyFoam .h3d files and mapping them to the current grid. This can be implemented using the HFILE option in the ASSIGN I/O Option and Subcase Information Entry. Currently, this is only for nonlinear static and nonlinear transient analysis.
Read elemental density from PolyFoam .h3d file and map the density to current mesh elements: ASSIGN, H3DRES, ID, <filename> in combination with MATUSR with FIELD continuation line can now be used to read the density from a PolyFoam .h3d file and map the values to the current grid. Valid for all analysis types for which MATUSR is supported (implicit analysis only).
Option to write only mass matrix or only stiffness matrix now supported: OUTPUT, MATRIX, <options>, STIFF or OUTPUT, MATRIX, <options> MASS can be used to output only mass or only stiffness matrix to the .full.mat or .reduced.mat file.
SPC force output now available for combined static subcases: SPC force output for combined static subcases via SUBCOM-SUBSEQ is now available in a .spcf file. Only applicable to STATIC subcases.
SUBCOM can now be used for static subcase with IMPORT card: SUBCOM and SUBSEQ combination can now be used with the IMPORT Subcase Information Entry. This is currently supported for static analysis only.
Subcase-dependent friction is now supported via SELECT: Subcase-dependent friction is now supported via the SELECT continuation line in the PCONT Bulk Data Entry. This definition should be used in combination with the SELECT Subcase Information Entry. This feature is currently supported for implicit nonlinear analysis.
Temperatures from an external H3DRES file can now be read and applied to IC as initial condition: Temperatures can be imported from an external H3DRES file and applied as an initial condition via IC(ASSIGN) = ID, where ID refers to the ID on an ASSIGN card. This feature is supported for heat transfer, nonlinear heat transfer, linear and nonlinear transient heat transfer analyses.
Support for MONDSP1, MONSUM, MONSUM1, and MONSUMT monitor point outputs: The use of MONDSP1, MONSUM, MONSUM1, and MONSUMT entries is now supported to monitor key displacement and summation-based responses during an analysis. These monitor points allow tracking of displacement components at specific grids, as well as summations of displacement results across multiple points or directions. The outputs from these monitor points are written into the *.monpnt file, following the same format and structure as existing MONPNT* entries.
Contact Scalar Integration of Contact Pressure over Surface (CICPS) is now available: Contact Scalar Integration of Contact Pressure over Surface (CICPS) can now be requested via the CONTF Subcase Information Entry (CICPS, OPTI option). It is currently only available in the OPTI format (.cntf file). It is currently supported for linear static analysis and nonlinear implicit analysis.
Note: In contact interfaces in which normal forces can act in tension (such as FREEZE contact, no-separation contact, and cohesive contact), the tension forces are currently counted in CICPS the same way that compression force (pressure) is counted, so the final CICPS scalar contact force for such contacts may be higher than expected.

Resolved Issues

In explicit analysis, the default MPC-based TIE is now automatically switched to penalty-based TIE when double dependency exists in the model.
Large positive clearance value now works as intended for CONSLI contact.
For global-local submodeling, the modal transient response local model no longer outputs zero valued results for the boundary grids.
Contact lock (CNTLCK) no longer encounters issues when run in DDM mode.
Models containing TIE with rotation wherein the secondary node is associated with RBE2 no longer encounter an error.
SPCFORCE output request no longer leads to a programming error for modal frequency response and random response analysis models.
SPCD now overwrites non-zero values of SPC applied in the same subcase in nonlinear transient analysis.
Acceleration output for internal nodes of DMIGs are now output for response spectrum analysis.
For models with ODS, there is no longer an issue with large disk space usage for DISP output request with PUNCH and PEAKOUT. Additionally, PRESSURE output is now included in the list of output supported for ODS.
Effective strain output in the H3D file from HyperForm is now recognized as equivalent plastic strain in OptiStruct. Additionally, both the top and bottom layer results are recognized.
The mapping of displacements into a local submodel is now correct when the enforced displacements are on nodes that are part of a contact interface in the global model.
Global-local submodeling with SPCD-M in local nonlinear static analysis model now leads to correct displacements.
TLOAD1/TLOAD2 with DELAY option in transient heat transfer analysis no longer leads to unexpected application of loading.
Models with AMSES eigensolver no longer fail if there is insufficient memory in the GPU. Now the model runs on the CPU if memory is not sufficient in the GPU.
When a CTRIA element is present at the end of a weld toe, an error is no longer issued.
A CMS generation run with MODEL=PLOTEL, NONE, NORIGID and GPFORCE(OP2) no longer leads to a programming error.
ACCEL loading in a model with topology optimization no longer leads to the model hanging in sensitivity calculations.

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.