Altair OptiStruct 2021.1 Release Notes
Highlights
- Aeroelasticity Flutter
- Combined Hardening Material
- Threaded Bolt
- MPC TIE for Large Displacement Nonlinear Analysis
- 1D Fluid for Thermal analysis (CAFLUID)
- Forced Convection Heat Transfer analysis for Topology optimization
New Features
- Preloaded Cyclic Symmetry
- Preloaded linear and normal mode analysis are supported. Preloading subcase is limited to linear subcase and can only include cyclic loading (Harmonic # 0).
- Shear and Volumetric test data for viscoelasticity
- Shear and Volumetric test data are supported for viscoelasticity
(MATVE) and frequency domain viscoelasticity
(MATFVE). For both entries, the
MODEL field can be set to:
- RTEST: Provides Shear and Volumetric test data for Relaxation.
- CTEST: Provides Shear and Volumetric test data for Creep.
- TOTALFORCE output
- TOTALFORCE is the sum of the applied force and the reaction force at any given grid points. This output is supported for linear and nonlinear static subcase in the .h3d file through the TOTALFORCE output request.
- Support preloaded dynamic analysis when preloading subcase is NLSTAT with INISTRS from forming simulation
- Preloaded normal mode analysis is now supported, even if the preloading subcase is nonlinear static and using initial stress input through INISTRS Subcase/Bulk Data pair.
- Hyperfoam
- Hyperfoam material type is supported with TYPE=FOAM in the MATHE Bulk Data Entry. Hyperfoam is supported for solid elements and axisymmetry, plane strain elements. Both direct parameter input and curve fitting through test data are supported for both implicit and explicit nonlinear analyses.
- Adaptive Penalty
- Adaptive Penalty for Nonlinear Contact analysis is supported and can be turned on by CONTPRM,TUNESTF,1 (“0” is the default and adaptive penalty is off by default). Adaptive penalty approach will adjust the contact penalty during Newton-Rapson iterations, while keeping the penetration within the user specified value. The maximum allowed penetration is chosen as MAXPNTRL*L, where L is the characteristic edge length (the average edge length on the main surface) of the contact. MAXPNTRL is defined through CONTPRM. Adaptive penalty approach can be tried in case the convergence difficulty is met with default linear penalty.
- New convergence criteria
- Maximum residual grid point force-based convergence criteria available with NLADAPT,ERRFINF,MAX. This is currently supported for Large Displacement nonlinear static and nonlinear transient analysis. This parameter supports input of two values: PARAM,ERRFINF,MAX,<FTOL>.
- Temperature-Dependent Hyperelasticity
- Temperature-dependent hyperelastic material are available via the new MATTHE Bulk Data Entry. All material models currently supported with MATHE are also supported on the new MATTHE entry which adds temperature-dependency. Currently, only direct parameter input is supported for MATTHE and table input for curve-fitting is not supported.
- MODCHG when the elements are attached to MPC or RBODY
- MODCHG is now supported when the elements to be changed are attached to MPC or RBODY.
- Contact interference
- Contact interference fit control is available with CNTITF Bulk and Subcase Entry. When there is an overclosure of contact surface, the contact interference fit is triggered automatically to resolve the overclosure. For this case, the overclosure will be resolved gradually over the subcase.
- Pressure-overclosure TABLE
- Pressure-overclosure relationship can be specified through TABLEG/TABLES1 and defined in PCONT.
- Threaded Bolt
- Threaded bolts can be defined as part of a CONTACT interface by setting the CLEARANCE field to reference a CLRNC Bulk Data Entry.
- Combined Hardening Material
- Combining hardening material can be used for analysis with cyclic loading, to capture shakedown, ratcheting effect, and so on. It consists of two nonlinear hardening rules, the nonlinear kinematic (NLKIN) and nonlinear isotropic (NLISO) hardening methods. Generally, the isotropic part is closely related to the von Mises criteria, and the kinematic part is described by the evolution law of back stress.
- 1D FLUID (CAFLUID)
- CAFLUID Bulk Data Entry is an 1D element with the ability to conduct heat and transmit fluid between its two primary nodes (G1 and G2). Heat flow occurs both due to the conduction within the fluid and the mass transport of fluid.
- Flutter Analysis
- Aeroelastic flutter is a dynamic instability of a structure associated with the interaction of aerodynamic, elastic, and inertial loads. Flutter analysis of aeroelastic systems involves determining the velocity (and hence Mach Number) of the system and the frequency of oscillation at which the system attains the state of flutter. In this phenomenon, the aerodynamic loads on a flexible body couple with its natural modes of vibration to produce oscillatory motions with increasing amplitude. This may lead to catastrophic structural failure. Therefore, structures exposed to aerodynamic loads must be carefully designed to avoid flutter.
- Strength Ratio output for PCOMPLS
- Strength ratio output for PCOMPLS with PARAM,SRCOMPS is now available.
- Max Stress Criteria with FT=STRS for PCOMP(G) and PCOMPP
- Max stress criteria with FT=STRS is now available for PCOMP(G) and PCOMPP.
- Convection Topology Optimization with Darcy Flow
- Forced Convection Heat Transfer is available via Darcy Flow analysis. Currently, this is supported for Linear steady-state heat transfer analysis only and both optimization and analysis only runs are supported.
- VERTEXM Free-shape
- The following enhancements have been added for VERTEXM free-shape
optimization.
- Pattern grouping (1, 2, and 3 plane symmetry are supported)
- GRIDCON with FIXED, VECTOR and PLANAR
- MMO for Global Fatigue response
- Multi-Model Optimization (MMO) now supports fatigue optimization with global fatigue constraints defined in the DTPL and DSIZE Bulk Data Entries.
- Modal damping based on mode ID
- Modal damping input for each mode ID (instead of frequency with TABDMP1) is available through the newly added TABDMP2 entry.
- Bolt Section output for 1D bolt
- Section coordinate system and Section resultant force summary are available .out file and .secres file for 1D pretension bolt section. The same results for solid bolt section has already been available in previous releases.
- Option to suppress mode output or adjust the printing frequency in .out file
- OUTPUT,MODES is now available, so that the normal mode results printing in the .out file can be suppressed (OUTPUT,MODES,NO) or the printing frequency can be specified (OUTPUT,MODES,n).
- AVL Excite support
-
- Structural damping for .exb file
- SET support for .exb file
- PARAM,EXCOUT is now obsolete and disabled
- PARAM,EXCOP2 is set to NO by default
- Force output in OPTI format .force file for Normal Modes Analysis
- Element force output for normal modes analysis in the .force file is available with OPTI output request.
- HDF5
- Available enhancements for HDF5 output (.h5 file)
are:
- Element force and stress for CBUSH elements
- PSD/RMS and cumulative RMS (Displacement, Velocity, Acceleration, and SPCF)
- Frequency response analysis results (Displacement, Velocity, Acceleration, and SPCF)
- CORD1R and CORD2R support
- MEFFMASS
- Modal effective mass output with MEFFMASS I/O Option Entry is now available. Additional options available in MEFFMASS compared to PARAM,EFFMASS is that MEFFMASS allows to specify a grid point as reference for the calculation of the rigid body mass matrix. The default is the origin of the basic coordinate system. Also, MEFFMASS has an option to output the results in the units of weight.
- PSD/RMS results for beam/bar
- Normal, shear and von Mises stress output on each evaluation point of beam/bar is supported for random response analysis in h3d.
- CBEAM axial stress in OPTI format output (.strs file)
- Axial stress/strain of beam is added at the end of line in .strs file for beam elements.
- PART Superelements
-
- The Bulk Data section in which CID is defined in GRAV/RFORCE entries can now be specified using the MB field. This feature is useful when loading needs to be defined in a fixed coordinate system, regardless of the orientation of the superelement, defined by a partitioned Bulk Data section.
- Original user ID is retained in H3D and punch output files for each part/superelement.
- In the H3D file:
- Each part/superelement has its own component/grid/element pool.
- Component labels are highlighted with its superelement
SEID.
For example, if original component name is PSHELL1 in superelement SEID=1, then in HyperView, the component label is displayed as (SE1) PSHELL1.
- In the punch file, SEID is printed in title/label section.
- String Label-based Input file definition
- Entities can be identified by string labels in their corresponding
ID field, in addition to the existing support of
integer IDs. While integer-based IDs offer more flexibility when the
input file is edited manually, string-based labels offer easier
identification of entries in the input file, especially when many
entries are defined. There are currently two types in which string-based
labels can be used.
- Type 1
- String labels can be used to identify entries via their corresponding ID field. For example, a string label in the MID field of MAT1 entry can uniquely identify this material entry.
- Type 2
- Entries defined with string labels as IDs can then be referenced by other entries using their unique string labels. For example, the string label identifier of a MAT1 entry can be specified on the MID field of a PSOLID entry,
- Memory option for MPI runs
- Memory option such as
-minlen
,-maxlen
,-len
,-fixlen
are now per-host instead of per-MPI process which was the case until the previous release.-hostmem=no
will revert to the per-MPI process memory allocation mechanism.
Resolved Issues
- Models with frequency-dependent materials previously showed sensitivity in results for repeated runs. That is, the same model running multiple times previously produced different results.
- ROMAX output through PARAM,ROMAX,YES no longer ends with a programming error.
- An MMO job no longer hangs after detecting an element distortion error.
- A plane strain N2S/S2S CONSLI model no longer fails with a programming error.
- H3D file from nonlinear analysis was not written out after the loss of license. Now the .h3d file will be written out, even if the loss of license occurs during the analysis.
- A Modal FRF model with EIGVSAVE/EIGVRETIREVE resulted in ERROR # 3478 in OptiStruct v2021 and v2020.1 while the same model ran in older versions.
- A nonlinear contact model with optimization encountered a programming error
in
igapst
datablock. - PARAM,AMSE4EFM no longer produces wrong results if there is viscous “B” option on PBUSH, with no value specified in that line (blank line).
- A programming error could occur if MFLUID Bulk Data is defined, but not referenced.
- With DOPTPRM,TOPDISC,YES, optimization restart run showed different density results at initial iteration than the last iteration in the original run.
- The thickness of RBODY influenced nonlinear analysis results, even if the thickness padding is “NONE” for contact.
- When there are multiple VABS cross-sections in a single deck, the VABS-OS run errored out with the ERROR # 5863. This has been fixed in the latest VABS code that is available on the APA download site.
- Preloading subcase with temperature-dependent material with TEMP(LOAD) through SYSSETTING,TLOADMAT updates the material properties properly.
- Translational JOINTG with MOTNJG(FIXED) in multiple subcases is respected.
- Mass from CBUSH is available in mass printing.
- The curve fitting process no longer fails for some models with Ogden hyperelastic material with ERROR #4905.
- Incorrect “HyperMesh Component weight table” in the .out file with DDM mode.
- The .mvw file is written out for modal analysis.