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.