Altair OptiStruct 2023 Release Notes

Highlights

Axisymmetry with torsion loading
Plasticity for beams
Direct reading of the RSP file for transient analysis
Milling manufacturing constraints
Optimization for electrical analysis
Mode tracking with a SET of elements

New Features

Stiffness, Strength, and Stability

Axisymmetry allowing torsion about the axis-of-symmetry: New general axisymmetric elements are now available which allow torsion loads about the axis of symmetry. The Quadrilateral general axisymmetric element (CQAXIG) and Triangular general axisymmetric element (CTAXIG) are now available for circumferential deformation. When compared to the 2D axisymmetric elements CQAXI and CTAXI, which have two degrees of freedom at each node, the general axisymmetric elements have an additional degree of freedom at each node circumferentially and can have torsional deformation about the axis of symmetry. The properties for general axisymmetric elements can be defined using PAXIG. If PARAM,AXI2DTOR,YES is present, 2D axisymmetric elements CQAXI and CTAXI are considered as general axisymmetric elements CQAXIG and CTAXIG (PAXI is considered as PAXIG).
Linear extrapolation for small displacement nonlinear analysis: Linear extrapolation via EXTRA=LINEAR on NLADAPT and NLCTRL Bulk Data Entries is now supported for both small and large displacement nonlinear analysis.
New JOINTG joint types: Three new JOINTG types are now available: The PCART (Projection cartesian joint), PFLTR (Projection flexion joint), and BUSHING (Bushing joint, which is a combination of PCART and PFLTR joints). These are supported for multiple JOINTG characteristics such as Motion, Stop/Lock, Elasticity, and so on. For more information, see the JOINTG Bulk Data Entry documentation.
JOINTG elastic force output: JOINTG elastic forces are now output in addition to the JOINTG forces (total joint forces) for nonlinear stiffness JOINTGs.
Contact wear output: Contact wear and contact wear loss volume outputs are now available. The WEAR continuation line on the CONTACT Bulk Data Entry is used to define the contact wear properties for output. The wear properties include wear coefficient (KWEAR), secondary side material hardness (HARDNESS), exponent on pressure in Archard wear equation (A), and exponent on sliding velocity in Archard wear equation (B). Contact WEAR output is included when the CONTF I/O Option is specified in the model.
Rayleigh damping support for JOINTG: JOINTG now supports Rayleigh damping. This can be activated by specifying PARAM,ALPHA2 to add the corresponding viscous damping to the JOINTG elements in the model.

Explicit Dynamic Analysis

Energy output in THIST file by component, property, or set of elements: Time history energy output for explicit analysis is now available by component, property, or set of elements. This is controlled by setting the ENTRY field to COMP, PROP, or ESET on the THIST Bulk Data Entry. COMP outputs the requested time history output for all components, PROP outputs the requested time history output for all properties, and ESET outputs the requested time history output for the specified element set ID. The ID is of a SET which contains a list of element SETs with Boolean OR.
Fully integrated shells: A new element formulation type is available for shell elements in explicit analysis, in addition to the existing Belytschko-Tsay (BT) and Belytschko-Wong-Chang (BWC) types. To activate fully integrated assumed strain shell element formulation, set the ISOPE field to FULL on the PSHELL Bulk Data Entry.
Slipring: Slipring joint on JOINTG is now available for explicit analysis. Set up the slipring joint by defining the JTYPE field as SLIPRING on the JOINTG Bulk Data Entry.

Noise and Vibration

MFLUID wet surface coarsening: The COARSE option is now available to scale the mesh size of the internally generated MFLUID surface mesh. Coarsening the MFLUID surface mesh can help improve the performance and reduce memory and disk usage. The Mesh Size Factor (MSF) scales the average mesh size of the input MFLUID surface mesh. The new coarsened mesh is generated internally by a lightweight SimLab mesher included in the HyperWorks Solvers installation. No additional user input is required for this.
PEAKOUT support for PFPATH: PEAKOUT is now supported in the PFPATH I/O Option. If PEAKOUT is present, the filtered frequencies from the PEAKOUT data are considered for output of transfer path analysis.
ERP, CMSE/CMKE/CMDE, MODALSE/MODALKE/MODALDE support in PEAKOUT Bulk Data Entry: The result type used for peak identification on the PEAKOUT Bulk Data Entry now also includes support for ERP, CMSE, CMKE, CMDE, MODALSE, MODALKE, and MODALDE. If ERP is defined, the PANEL continuation line can be used to identify the Panel or Grid ID for the ERP response. If CMSE, CMKE, CMDE, MODALSE, MODALKE, or MODALDE are defined, the MODE continuation line can be used to identify the Superelement or Mode for output to be used for PEAKOUT filtering.
Dynamic stiffness output: Dynamic stiffness output is now supported via the KDYN output request. It is calculated as the reciprocal of the displacement. It is currently supported for frequency response analysis and is available in H3D and Punch formats.
DDM support for preloaded CCMS analysis: DDM is now supported when Component Mode Synthesis (CMS) reduction subcase contains a preload from linear static or nonlinear static analysis. One of the important use cases is using DDM for CMS reduction of a large model where the preloading comes from nonlinear static analysis.

Heat Transfer Analysis

Auto-time step: Automatic Time-stepping is now supported for both Linear and Nonlinear Heat Transfer analysis using the reference temperature method. It is not turned on by default, and can be activated by setting the MFREF field to 1 on the TSTEP Bulk Data Entry.
Repeated thermal cycle: One Step Transient Thermal Stress setup (OSTTS) can now be setup with repeated thermal cycles in structural load steps. The HST field on the TEMPT Bulk Data Entry can now be set to MHSUB to indicate the thermal load is read from multiple transient heat transfer subcases. The HSUB parameter references the identification number of a transient heat transfer subcase. The REPEAT parameter identifies the number of repeated cycles of temperature history from the specified transient heat transfer subcase, to be applied within the specified time period. The TEND parameter is available to define the end time of the period that the thermal load is applied.

Optimization

Milling constraints: The MILL continuation line on the DTPL Bulk Data Entry is now available to define milling constraints for topology optimization. There are two ways to define milling constraints: using the access angle (ANGLE), or using the bit and clamp dimensions (R, B, and H). The access angle (ANGLE) is defined as the ratio of radius of the outer circle to the depth of the milled hole. R is the radius of the mill bit, B is the length of the mill bit, and H is the radius of the mill head. Obstacles which define non-designable properties can be defined using the OBST continuation line.
Mode tracking for set of elements: Additional control for Mode tracking in optimization with eigenvalue analysis is now available via the new MODTRAK Bulk Data Entry. The MODTRAK Subcase Information Entry should be used to reference the MODTRAK Bulk Data Entry. The MODTRAK Bulk Data Entry also contains the TRAKSET field to define an Element SET ID to define a specific part of a model for mode tracking. This enables component-level mode tracking.
Electrical analysis: Optimization is now supported for electrical analysis. The Topology, Shape, Free-shape, Size, and Free-Size optimization design variables are supported. Two responses are currently supported. The Nodal Electric Potential response can be activated by setting the RTYPE field to ELPOT on the DRESP1 Bulk Data Entry. The GRID ID can be defined on the ATTi field. The Global Electric Compliance response can be activated by setting the RTYPE field to ELCOMP on the DRESP1 Bulk Data Entry. DRESP2 and DRESP3 Bulk Data Entries are also supported. Optimization for electrical analysis is supported for all element types and is currently only supported for linear steady-state electrical conduction analysis. Temperature dependency and electro-thermal coupling are not currently supported.
Include nominal design in DGLOBAL: New options is added on the DGLOBAL Bulk Data Entry to include the nominal design in the starting points. This option can be specified in the eighth field as YES/NO, with NO as the default option. When the mode tracking is used for DGLBOAL optimization and the nominal design is used as starting points, the modes calculated with nominal design are used as reference modes for mode tracking in any subsequent optimization with different starting points.

General

OLOAD output in FORCE/MOMENT Bulk format

New BULK and LOADID options are now supported for OLOAD output for FORCE and MOMENT outputs. If the BULK option is present in the OLOAD output request, the FORCE and MOMENT loads are written to a new ASCII file named filename.loadbulk. If LOADID=<ID> is defined in the same OLOAD request, the printed FORCE/MOMENT ID in the filename.loadbulk file is based on this ID as follows:

If LOADID=<ID> is defined, the ID of FORCE/MOMENT entries in the filename.loadbulk file is equal to ID from LOADID + Load ID of the subcase (the Load ID of the subcase is the ID referenced by the LOAD entry in the subcase).
If LOADID is not defined, the ID of FORCE/MOMENT entries is equal to the Load ID of the subcase (referenced by LOAD entry in the subcase).

RSP/RPC files as loading for transient analysis

The RSP file can now be used as loading and OptiStruct internally sets up the transient loading. The ASSIGN,EXTLOD entry can be used to identify the RSP or RPC file and mapping CSV file for the external loading. Additionally, the ID of the ASSIGN entry can then be referenced on a TLOAD1 entry in the transient analysis setup in the EXCITEID field. The TLOAD1 entry should have the TYPE field set to EXT to indicate the load is coming from an external file. Both direct and modal transient analyses are supported. The DELAY field on the TLOAD1 entry is supported for external loading (negative delay can be used to skip data in the RSP or RPC file which are not necessary).

Example:

ASSIGN,EXTLOD,102,’load.rsp’,’mapping.csv’
…
SUBCASE 1
…
BEGIN BULK
…
TLOAD1,13,102,,EXT

Plasticity for beam

The integrated beam formulation is now available for TYPE=ROD and TYPE=BAR for both implicit and explicit analysis. In this case, the beam is computed using cross-section integration. The integration points are automatically distributed in the section according to the quadrature order and the type of the section. The Quadrature order can be controlled using the Q_ORDER field on the INT continuation line in the PBEAML Bulk Data Entry.

ERP output support for transient analysis and steady subcase type

ERP output is now supported for transient analysis and steady-state analysis. For steady-state analysis, the currently supported outputs are displacement, stress, and ERP.

Stress/strain for random response in OPTI format

Stress and strain results are now available in OPTI format for random response analysis.

Transient results in OPTI format

OPTI format output is now supported for transient analysis, and the following outputs are supported: Displacement, Acceleration, Velocity, Stress, Strain, and Force.

PUNCH output by subcase

OUTPUT,PUNCH,BYSUB is now supported for all analysis types for which PUNCH output is supported. A filename_s#.pch file is output for each subcase where # is the subcase ID. Additionally, POST,TOFILE is now supported for additional analysis types. When both OUTPUT,PUNCH,BYSUB and POST,TOFILE are defined, POST,TOFILE takes precedence (wherein multiple subcases can be output in a single punch file if they have the same POST,TOFILE defined).

Reduced loading output in op4 file with PARAM,EXTOUT,DMIGOP4

Loading can now be reduced in the OP4 file using PARAM,EXTOUT,DMIGOP4 along with CMSMETH and the loading from the DMIG can then be used in the residual run with P2GLOAD.

Automatically adjusted grid coordinate for CBUSH to make non-zero length CBUSH

SYSSETTING (ZEROLBUSH=value) has been added for this release. If the length of CBUSH is less than the value, the coordinate of GB on CBUSH is replaced by the coordinate of GA.

Resolved Issues

Temperature results during a nonlinear heat transfer analysis with temperature-dependent specific heat no longer show an issue.
Strain energy results (ESE) are now correct when used together with PEAKOUT.
Strain energy of superelement/DMIG (CMSE) are now correct if DMIG is generated with CBN method.
Error #6114 now occurs correctly to indicate that a section definition is invalid.
Pin flag option on beam in explicit analysis now works as expected.
Programming error no longer occurs with STEADY analysis when the model has DMIG.
DOPTPRM,TOPDISC option no longer affects the results of free-size optimization.
Error #5127 no longer occurs in Darcy flow model when MAT5.
Programming error no longer occurs in a radiation to space heat transfer analysis when the initial condition is used to refer to the temperature in previous subcase.
Internally generated grid IDs in the _nl.out file have been removed.
MOTNJG no longer uses the position of the previous load case when FIXED is selected even if CNTNLSUB is not defined.
A particular mode is now properly post-processed in HyperView with the .h3d file in case there are repeated modes (same frequencies).
The results accuracy with PARAM,VMOPT,2 with SPCD loading has been improved.
The performance for frequency response analysis with pressure loading has been improved.
Error #1898 from optimization with frequency response and random response using Von Mises and principal stresses/strains responses no longer occurs.
Composite bond failure is now available in the .h3d file even if the values are all zero.
Shear strain calculation is no longer incorrect for PBEAML BAR cross section.
TIE contact now works correctly when one side of TIE is very soft.
Very large disk space is no longer required for transient subcase if a static subcase with pretension bolt is included.
Von Mises stress calculation for BOX/BOX1 section is now correct.
MFLUID with PARAM,VMOPT,2 in dynamic reduction (CMSMETH) with ASET has been revised to improve the accuracy.
Electrical anisotropic material with cylindrical coordinate system now works correctly.