Altair OptiStruct 2022.1 Release Notes

Highlights

Piezoelectricity
New Nonlinear Convergence Criteria Control (NLCTRL)
New Creep Material (Anand, Darveaux)
Deformation Gradient Tensor
Axisymmetric Elements for Heat Transfer
APML (Adaptive Perfectly Match Layer) for Exterior Acoustics

New Features

Stiffness, Strength and Stability

New Nonlinear Convergence Criteria Control, NLCTRL

Newly added Bulk/Subcase Entry, NLCTRL, supports different convergence criteria than existing nonlinear convergence criteria in NLPARM Bulk Data Entry. The criteria are based on the displacement and the residual force. NLPARM will continue to be supported and can be used in Nonlinear Analysis. NLCTRL Bulk Data Entry supports existing convergence criteria on NLPARM, and in addition, also supports all the existing options available in NLADAPT. Therefore, there is no need to use both NLCTRL and NLADAPT or NLCTRL and NLPARM at the same time. An error message will appear if NLCTRL and NLADAPT or NLCTRL and NLPARM are used in the same subcase.

Shell to Solid connection with RSSCON1

RSSCON1 is a more user friendly definition of shell to solid connection than existing RSSCON, where the solids and shells that need to be connected are defined through the SURF Bulk Data Entry with RSSCON1. It also allows the connection in case the multiple layers of solids need to be included in kinematic condition because the thickness of shell is large and also RSSCON1 is supported for large displacement nonlinear analysis while RSSCON is not.

New Creep Material, Anand and Darveaux

Anand and Darveaux creep material are available as new creep material type in MATVP.

Deformation Gradient Tensor in User Material, MATUSR

Deformation Gradient Tensor is supported for user material MATUSR as arguments in the user material subroutine. The dfgrold and dfgrnew arguments are now available to define the deformation gradient tensor of the previous increment and the deformation gradient tensor of the current increment.

Utilization factor output

UTIL option in CONTF contact force output will trigger the output of utilization factor and shear magnitude.

Shear magnitude is the summation of grid shear force. Utilization factor is given by:(1)

U = [\frac{\frac{\sum G r i d s h e a r f o r c e}{F r i c t i o n C o e f f i c i e n t}}{\sum G r i d n o r m a l F o r c e}] = \frac{\frac{S h e a r m a g n i t u d e}{μ}}{\sum F_{n}}

Utilization factor (U) is a quantitative measure for determining the load increment at which sliding has occurred (if any). When the utilization factor gets closer to one, sliding occurs.

Currently supported output formats are:

Result Type: Comments
Shear utilization factor: It is available only in H3D and OPTI formats.; In H3D format, it is output on each node.; In OPTI format, it is output for each contact interface.
Shear magnitude: It is output for each contact interface and is available only in OPTI format.

Contact pressure dependent Contact Status in preloaded analysis

CNTLCK Bulk Data Entry is now available and used to specify the contact pressure threshold. If the contact pressure from the nonlinear analysis is larger than the threshold defined in CNTLCK, the contact is assumed to be closed in subsequent preloaded linear analysis (such as preloaded Modal Frequency Response). This CNTLCK Bulk Data Entry should be referenced by CNTLCK Subcase Information Entry in the preloading Nonlinear Static Analysis subcase (small and large displacement analysis are supported). The contact lock is then applied to the preloaded Linear Analysis subcase, which is preloaded by the corresponding Nonlinear Static Analysis subcase that contains the CNTLCK Subcase Information Entry.

User-defined State variables label for MATUSR/MATUSHT

Subroutine initusr can be called from MATUSR/MATUSHT user subroutines to define user-defined label for state variables.

Shell elements can be defined in the pretension bolt

Shell elements are now supported in pretension bolt. The Error message has been removed, even if shells (typically membrane) are defined in the bolt defined with PRETENS.

Contact Friendly elements (CONTFEL) activated automatically for N2S and second order solids

Contact Friendly elements (CONTFEL) will be activated automatically for N2S and second order solids in model, even if the DISCRET field is blank on the CONTACT/TIE entries.

Kinematic and Mixed hardening plasticity for shells

Kinematic and mixed hardening for elasto-plasticity material is now supported for 1^st order shells in small displacement nonlinear static/transient analysis.

Second order shells support for MODCHG

Second order shells support for MODCHG.

Moment output support for Contact

Moment output is available for Contact with CONTF output request in .cntf file. Moment output is only available when the continuation line MNTREF in CONTACT Bulk Data Entry is defined.

The reference point of moment calculation can be specified several ways, such as the user-defined grid ID, the center of contact, the origin of the model and the user-defined coordinates (x,y,z).

Nonlinear Restart enhancement

Nonlinear Restart supports Moment Bulk Data Entry and fluid elements.

Explicit Dynamic Analysis

JOINTG for elastic bodies instead of only on rigid bodies: JOINTG is now allowed to be defined on elastic bodies.
CBUSH without mass is supported: CBUSH now works without any user-defined mass in PBUSH.

Heat Transfer Analysis

Axisymmetric elements for Heat Transfer Analysis: Axisymmetric elements are now supported for any Heat Transfer Analysis. Thermal contact (both node-to-surface and surface-to-surface) is also supported for heat transfer analysis with axisymmetric elements.
STATSUB(STRUCTURE) for Transient Heat Transfer: STATSUB(STRUCTURE) can be used to carry over the CONTACT/GAP status from the preceding nonlinear analysis. STATSUB(STRUCTURE) is now supported for any heat transfer subcase.
Composite (PCOMP, PCOMG, PCOMPP/STACK) support for Heat Transfer: Composite properties are supported for Heat Transfer Analysis.
Power output with SPCF for convection ambient point in Steady-State and Transient Heat Transfer Analysis: Power output for convection ambient point is available with SPCF output request.

Noise and Vibration

APML (Adaptive Perfectly Matched Layer) for Exterior Acoustics

A new exterior acoustics solution, Adaptive Perfectly Matched Layer (APML) is now available. It is an extensively used solution in the exterior acoustics field. APML enables excellent improvement in performance efficiency (compared to Infinite Elements), while maintaining accuracy, by leveraging the technique of frequency band generation in conjunction with automatic adaptive mesh generation for each frequency band. A lightweight SimLab mesher is embedded with the OptiStruct installation, allowing for seamless adaptive meshing dynamically in real time. The acoustic pole coordinates are also internally calculated by APML (in contrast to IE).

The APML setup is straightforward (and similar to IE), wherein you need the following data:

Create an acoustic cavity mesh which fully encloses the vibrating structure of interest.
Create a boundary PML mesh layer using CACPML3/4 elements at the outer surface of the acoustic cavity mesh.
The PACPML property entry is associated with the CACPML3/4 elements to define the APML properties.
Frequency-band generation is active by default using the ADAPF method, but additional control is available via the PACPML entry, or the frequency bands can be defined directly using the MESHF entry.
The microphone grid points can be defined for acoustic output requests (similar to IE).
The sound pressure (DISP) output is currently supported for APML.
The lightweight SimLab mesher is used to internally generate the various adaptive meshes without requiring any additional user input.

Automatic adjustment of Normal direction of panels for ERP

The normal direction of elements in panels will automatically be flipped in case they are not consistent across the panels used for ERP. This is required for ERP output.

Area output for PANEL used in ERP and the automatic output of sum of all ERP PANEL contributions

For ERP application, the following output is now available automatically in punch file:

Area output for each panel
Total ERP from all panels

Unconnected parts output with AMSES

PARAM,CHKUCON is available to output unconnected parts during an AMSES run.

JOINTG force output in h3d file for Frequency Response and Random Response

JOINTG force in Frequency Response and Random response (PSD/RMS) are available in h3d file when the STRESS output entry is specified.

Subcase-dependent RESVEC’s for multiple Modal Frequency Response and Transient Response

With multiple dynamic response subcases, the union of RESVEC (residual vectors) from all subcases are used for all the subcases, which is the default behavior. If PARAM,SUBRESVC,YES is used, the residual vectors generated from a particular subcase will be used for that subcase only, instead of using the union of residual vectors from all the subcases.

PARAM,FCACSV,YES

Fluid-structure complex eigenvalue analysis runs previously generated a *.cmode.csv by default, which contains mass fraction, MAC, and so on. This file is now only available when PARAM,FCACSV,YES is defined in input file.

Fatigue

Multi Haigh with constant R ratio: For damage evaluation using multiple Haigh diagram in MATFAT, a new interpolation method is added, which is based on constant R ratio in addition to the existing interpolation method of constant mean stress.
Multi-SN curve support for Multi-Axial SN fatigue and Random, Sine Sweep Fatigue: Multi-SN curve is supported for Muti-Axial SN fatigue and Dynamic Fatigue such as Random and Sine Sweep fatigue.

Optimization

Error messages in Multi-Model Optimization (MMO) printed in the main process: Any error messages that occur in secondary processes are now also printed in the main process for MMO.

General

Piezoelectricity: Piezoelectric materials are a class of materials in which structural deformation triggers electrical potential and vice versa. OptiStruct supports two-way Piezoelectric coupling in which a mechanical excitation will generate an electrical response. Conversely, an electrical excitation will generate a mechanical response. The coupling is strong, which means that both mechanical and electrical responses are solved simultaneously.
TEMPADD: Multiple TEMP Bulk Data Entries can be combined by using the newly introduced TEMPADD Bulk Data Entry. The TEMPADD Bulk Data Entry can be referenced anywhere the TEMP or TEMPD Bulk Data Entry can be referenced.
Electrical Conduction Analysis results: For the Multi-Steady Electrical Conduction Analysis coupled with heat transfer analysis, the electrical conduction results are available in its own subcase, instead of being included in heat transfer analysis subcase results.
Disk space reduction for AVL EXCITE interface jobs: AVL EXCITE interface jobs with PARAM,EXCEXB now requires the minimum amount of disk space needed to complete the job.
Make the corner stress default with OptiStruct.cfg file: OutStress option in the OptiStruct.cfg file allows the specification of selected default location options for stress output. Locations now supported for the new OutStress option in the configuration file are CORNER, BILIN, CUBIC and SGAGE.
Disable the output of automatic bolt force output in .secres file: NOBOLT option in RESULTANT output request will disable the automatic bolt force output in the .secres file. That is RESULTANT(NOBOLT) = ALL.
MIRROR option in DMIGMOD: DMIGMOD RELOC option now has the MIRROR option, which can be used to mirror the superelement.
GRID SET support for Initial Condition (TIC): GRID SET is supported for Initial Condition Bulk Data Entry, TIC for both implicit and explicit analysis. If the GSET flag is specified, the corresponding ID specified on the GID/GSETID field identifies a GRID SET.
Temperature loading support for Linear Transient Analysis: Temperature loading is supported for Linear Transient Analysis with TLOADi Bulk Data Entry. The TEMP/TEMPD/TEMPADD Bulk Data Entries can be referenced on the TLOADi Bulk Data Entry, which can then be referenced on the DLOAD Subcase Information Entry in a Linear Transient subcase.
JOINTG contribution in Grid point force (GPFORCE) in h3d, punch and gpf file: JOINTG contribution is included in GPFORCE output and labeled as RJOINT.
Compliance calculation with temperature loading: The accuracy of compliance calculation with temperature loading has been improved.

Enhancements

Accessing Tutorial Model Files: You can now click a link, within a tutorial, to download the required model file(s) for that tutorial.
Important: This download option is only available if you (or any user) are connected to the internet. Users attempting to download a model file will be prompted with further directions on how to access the model file online. A zipped package of the model files can be downloaded from the Altair One Marketplace and extracted to a local machine or directory on your company’s local server.

Resolved Issues

Thermal material user subroutine (MATUSHT) no longer produce incorrect results, if HGEN is provided as PROPERTY to MATUSHT.
The following issues are fixed for Component-based Effective Mass output through MEFFMASS.
- The results could be incorrect unless the strain energy or kinetic energy is requested.
- Modal participation ratio in .mvw file could be incorrect.
PFPANEL results are correct, if PARAM,ASCOUP,NO is used and also AMSES/AMLS is used as eigenvalue solver with a reduced output set.
RMS SPCF in Random analysis could be zero, unless SPCF is also requested for FRF subcase. This has been fixed.
PFMODE model no longer encounters a programming error, if there are many subcases and the number of grids in GRIDC is large.
Adjust option in CONTACT works properly for large displacement nonlinear analysis.
Programming error no longer occurs with Hyperelastic material (MATHE) and MODCHG.
Explicit dynamic analysis results are correct, if certain subcases have initial conditions and other subcases do not.
RMS/PSD Corner stress for solid elements.
The job completes, if PHASE option is specified with SPCD in Frequency Response Analysis.
Nonlinear Restart job with RESTARTR no longer fails.
Modal Frequency Response job completes when energy output is requested.
Automatic conductivity calculation with KCHTC=AUTO has been improved, even if the material has temperature-dependent material with MATT4.
Normal modes analysis with GPU job produce correct results.
Electrical material input for PCOMP(G)/PCOMPP was treated internally as resistivity instead of conductivity and this has been fixed.
Contact element contribution for moment in grid point force balance table is no longer missing.
Current density for solid element in multi-step electrical analysis is applied properly.