What's New

View new features for OptiStruct 2020.

Altair OptiStruct 2020 Release Notes

Highlights

Plane strain element for Nonlinear Analysis
Cohesive Zone Modeling with contact
Contact for axisymmetric elements with continuous large sliding
Temperature-dependent convection coefficient
Radiation to space
String (label)-based input file definition – Beta Feature

New Features

Stiffness, Strength and Stability

Plane strains: Plane Strain elements are now available for Linear/Nonlinear Static (both SMDISP and LGDISP), Dynamic Analysis (Normal modes, Transient, and Frequency Response). For nonlinear analysis, contact is also supported (node-to-surface only is supported. Both small sliding and large sliding with continuous sliding (CONSLI) are supported).; Element Bulk Data: CQPSTN and CTPSTN (both 1st and 2nd order); Property Bulk Data: PPLANE; Supported material types: MAT1, MATS1, MAT3 and MATHE (first order); Supported loading: FORCE, MOMENT, PLOADE1, PLOADSF (follower effect is supported)
Large Displacement Analysis support for Viscoelasticity (MATVE) and Creep (MATVP): Is now available.
Note: Viscoelasticity and creep are currently only supported for solid elements.
Support for Hyperelastic Material (MATHE) along with Viscoelasticity (MATVE): The Hyperelastic material (MATHE) provides the instantaneous response, while the Viscoelastic material (MATVE) defines the relaxation.
Extended Beam pin flag support for Large Displacement nonlinear Analysis: Any combination of Pin Flag options on CBAR/CBEAM elements is supported for large displacement nonlinear analysis.
Axisymmetry with large sliding: Large Sliding contact for axisymmetry nonlinear analysis is supported. The supported large sliding contact type is continuous sliding (CONSLI). This is supported for node-to-surface contact (N2S).
Elasto-Plastic material for 1D (beam, bar and rod): Elasto-plastic material (MATS1) is supported for 1D elements. Currently, the yield stress only considers axial stress of 1D elements.
Cohesive Zone modeling with Contact: Cohesive Zone modeling can now also be accomplished using Contact instead of cohesive elements. The COHE continuation line is now available on the CONTACT Bulk Data Entry and the corresponding MCOHEDID field can reference the MCOHED Bulk Data Entry.
Temperature loading output: Temperature loading such as TEMP(D) can be output with OLOAD output request.
Enhanced Thermal Strain calculation: New thermal strain calculation is introduced with PARAM,THMLSTN,1. This PARAM is only available for nonlinear static analysis.; With PARAM,THMLSTN,0 (default), the thermal strain calculation will remain the same formulation as the previous versions.
Temperature loading as external file: Temperature results from an external source in punch file (transient) format can be used as the loading for nonlinear static and transient analysis. Temperature in punch format can be read thru ASSIGN,HFILE. New Bulk Data TEMPT is introduced which references the ID of ASSIGN,HFILE. TEMPT also allows the mapping of temperature results in certain time frame to a specific time frame in structural analysis subcase.; TEMPT can also reference a subcase ID with HSUB keyword. This is the same setup as the One Step Thermal Transient and Structural Analysis (OSTTS), but allows more control of mapping of different time scales between heat transfer transient subcase and nonlinear structural subcase.
Enhanced One Step Thermal Transient and Structural Analysis (OSTTS): Time-dependent loading with TLOADi/DLOAD for Nonlinear Structural static subcase in OSTTS is supported.
No Search Distance required when CLEARANCE is defined: Search Distance for contact is not required if SYSETTING, SRCHDCLR is set to YES and CLEARANCE is defined. In this case, all contact elements within a CONTACT interface (where CLEARANCE is defined) will be generated as if the search distance is set to an infinitely large value. SRCHDCLR can also be set in .cfg file so you can avoid specifying this SYSSETTING in each input file.
Adaptive Time Step support for Small Displacement Nonlinear Transient: Adaptive time step is supported for Small Displacement Nonlinear Transient analysis. Default is on and MREF on TSTEP Bulk Data is effective for small displacement nonlinear transient analysis too.
Summary printing for follower loading: Summary of follower loading for large displacement nonlinear analysis is printed in the .out file.

Enhancements

First Order Tetra (TET4) element support: Supported for Explicit Dynamic Analysis.
Single Precision executable support: Is now supported. Executable will have “_sp” in its name. “-sp” solver script option can be specified to use single precision executables.
Penalty-based TIE Contact: Available for Explicit Analysis and is used automatically when there is over-constraint in the model. Default TIE is still kinematic-based.
Critical Time Step output: Critical time step (nodal or elemental) for explicit analysis will be output in the .out file. This output is also available after a check run (-check script run option).
Edge to Edge Contact for Solids: The PSURF continuation line is available on the CONTACT Bulk Data. PSIDi entries can reference PSURF Bulk Data IDs.

Heat Transfer

Thermal Contact support for Linear/Nonlinear Transient Heat Transfer Analysis: Is supported.
Temperature-dependent Convection Coefficient for Steady-State and Transient Heat Transfer Analysis: Convection coefficient on MAT4 can be temperature-dependent for Steady-State and Transient Heat Transfer analysis. Table input is required and referenced by the corresponding MATT4.
Temperature-dependent Specific Heat: Specific heat on MAT4 can be temperature-dependent. Table input is required and referenced by the corresponding MATT4.
Radiation to Space: Radiation to Space for Steady-State Heat Transfer Analysis is supported.; Radiation boundary conditions can be specified with RADBC Bulk Data where the radiation view factor is defined and the RADBC entry should be referenced by a CHBDYE entry. In addition, the RADBC entry points to a grid for ambient temperature definition and the ambient temperature can be specified with SPC.; The emissivity and absorptivity material surface properties are specified on the RADM Bulk Data Entry. The RADM entry is directly referenced by a surface element entry (CHBDYE).; PARAM,TABS defines the absolute temperature scale and PARAM,SIGMA defines Stefan-Boltzman constant.

Rotor Dynamics

Enforced motion (SPCD) for Modal Frequency Response: SPCD is supported for Rotor Dynamics with Modal Frequency Response.
Rotor Energy: Rotor Energy with RENERGY output request is supported for a model with DMIG or GENEL.

Optimization

CGAP Axial U response: Axial U (displacement) response is supported for CGAP(G). RTYPE in DRESP1 is FORCE and ATTA is UAX.
Large Shape Change for Frequency Response Optimization: Some special sensitivity analysis is required for shape optimization that involves CGAP(G), CWELD, CFAST or Node-to-Surface CONTACT in order to allow very large shape changes. This special shape sensitivity is now available for optimization with frequency response analysis.
Large Shape Change for Heat Transfer Optimization: Some special sensitivity analysis is required for shape optimization that involves CGAP(G), CWELD, CFAST or Node-to-Surface CONTACT in order to allow very large shape changes. This special shape sensitivity is now available for optimization with Heat Transfer analysis.
Parallel Computation for MFD, SQP Optimizers: Is supported with DOPTPRM,OPTIMOMP,YES. The number of cores for parallel computation is specified with -nt script option.

General

Integration with VABS

OptiStruct and VABS are integrated to analyze slender structures via the latter’s ability to compute the complete set of beam section properties for an arbitrary cross-sectional shape and material without any ad hoc kinematic assumptions.

VABS (Variational Asymptotic Beam Sectional Analysis) is a cross-sectional analysis tool for computing 1D beam properties and recovering 3D stresses/strains of slender composite structures (and isotropic materials). VABS is a product from AnalySwift and is now part of the Altair Partner Alliance products.

With this integration between OptiStruct and VABS, users can perform analysis of curved and twisted composite beams in a single seamless run of OptiStruct, where VABS is invoked internally. The VABS libraries are placed in the installation directories at the following location:

For Windows:: <HyperWorks_install_directory>\hwsolvers\optistruct\lib\win64\VABS
For Linux:: <HyperWorks_install_directory>/hwsolvers/optistruct/lib/linux64/VABS

OptiStruct automatically finds this library and launches VABS.

HyperMesh version 2020 is also enhanced to generate a finite element mesh of the cross-section (needed as input for VABS), including all the details of geometry and material as inputs to calculate the sectional properties. VABS compatible input file is saved in a prescribed working directory.

OptiStruct identifies the VABS inputs through ASSIGN,VABS, and solves and generates equivalent stiffness matrix invoking the VABS executable. PBEAML property in OptiStruct input file is needed where the GROUP field is VABS and the TYPE/NAME field would be the section name assigned on ASSIGN,VABS.

OptiStruct further reads VABS output and executes the full solver run.

String (Label)-based Input file definition

Entities can now be referenced by string labels in the ID field, in addition to existing integer .Currently, support is available for:

Category: Entity
Materials: MAT1, MATS1, MAT2, MAT3, MAT4, MAT5, MAT8, MAT9, MAT10
Properties: PSHELL, PSOLID, PBEAM, PBAR, PBEAML, PBARL, PBUSH, PCOMP, PCOMPG, PROD, PELAS, PDAMP, PMASS, PGAP
Sets: GRID, ELEMENT
Coordinate system: All coordinate systems
Others: PLY

The above entries can be referenced with string labels in the following:

References

Materials

String labels in the material ID field of corresponding properties are supported.

Properties

String labels in the property ID field of corresponding elements are supported.

Sets

String labels in the set ID field of the following bulk entries are supported: SPC, SPCD, FORCE, MOMENT, PLOAD1, PLOAD2, ACCEL2.
String labels in the set ID field of output requests are supported.

Coordinate system

String labels in the coordinate system ID field of JOINTG entry is supported.

PLY

String labels in the PLY ID field of STACK entries are supported.

String labels characteristics

They are case insensitive.
String labels are supported in all the Bulk Data formats namely, fixed, large fixed (long) and free formats.
For string labels longer than 8 characters, it is recommended to use the free format. While strings of any length are allowed in the free format, they will be truncated after 16 characters when processed within OptiStruct.
They follow the same guidelines as variable names in the existing symbolic substitution feature.
HyperMesh support for string labels will be available in a future release.

Subcase-dependent Non-Structural Mass (NSM)

Is supported for Linear/Nonlinear Static Analysis. The model will error out, if NSM is defined inside any subcase other than Linear/Nonlinear Static subcase.

AUTOMSET

Now supported for models with JOINTG.

PSD/RMS SPCF output

For Random Response Analysis is now supported.

Total Memory Requirement output per node for DDM run

Total memory required for DDM jobs per node is available and printed in the .out file.

Failure Mode output for HASHIN

Output for each mode of failure (Fiber tension/compression and matrix tension/compression) is available in the .h3d file for post-processing.

1D von Mises stress output for Response Spectrum

von Mises stress for CBAR/CBEAM with PBARL/PBEAML is available for Response Spectrum Analysis.

Transient Statistics output

Support for statistical output request is available in case of Direct and Modal Transient Analyses in the .h3d file format.

Output Request	Result Type	Statistical Results Available
CSTRESS	von Mises Stress (available in the individual plies) Principal Stress Normal stresses (Composite Stresses) in material/ply coordinate system	Maximum, Time of Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum, Mean, RMS, Variance, Standard Deviation
SPCF	Magnitude For X, Y and Z components	Maximum, Time of Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum
ACCELERATION	Magnitude For X, Y and Z components	Maximum, Time of Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum
ELFORCE	Magnitude For X, Y and Z components	Maximum, Time of Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum
DISPLACEMENT	Magnitude For X, Y and Z components	Maximum, Time of Maximum Maximum/Minimum/Absolute Maximum, Time of Maximum/Minimum/Absolute Maximum

Statistical output can be requested with the statistics argument via the following options:

STATIS – Statistic results are output in addition to the regular output at each timestep, for the selected entity.
OSTATIS – Only statistical results are output for the selected entity.

Element Force/Stress Calculation considering Damping contribution

PARAM,GE4TRSTF for Transient Analysis and PARAM,GE4FRSTF for Frequency Response Analysis. The default value for these parameters is 0.
If the value is set to 1, then the GE coefficient is taken into account while computing stresses and element forces (can be material/property/NSGE and so on).
The element forces for CDAMP1, CDAMP2, CVISC and viscous contribution to CBUSH are calculated and output for linear transient analysis.

Enhanced Mid-edge nodes GPSTRESS output for 2nd order solids

PARAM,EDGESTR,ELEM/NODE is added as the switch for grid point stress calculation for mid-edge nodes.
EDGESTR=ELEM is the improved method and set as default. The stress at edge is calculated from elemental corner stress first, then averaged between connected elements. The grid point stress at edge might be greater than the stresses at the corners.
EDGESTR=NODE is the original method. The grid point stress at edge is calculated directly by averaging the grid point stresses at corners

Enhanced Interface with Multiscale Designer (MDS)

The interface has been enhanced and simplified by now using MATMDS Bulk Data Entry, instead of the old method where MATUSR was used.
Material data from MDS can be saved in any location on your machine and selected with ASSIGN,MATMDS.
The LOADLIB entry is not required anymore. OptiStruct searches for the required library in the same HWSolvers installation. The MDSDIR I/O Entry can be used to identify the MDS installation, if OptiStruct and MDS are in different installation locations
Example:

ASSIGN,MATMDS,Name of Material, MDS material data

MDSDIR = C:\Program Files\Altair\2019\hwsolvers\MultiscaleDesigner

OLOAD can retain the force applied on single point constraints (SPC)

New options have been added to the OLOAD entry.

NOSPC (default)

Force applied on SPC will be zero.

SPC

Force applied on SPC will be retained.

Random Response Fatigue without rerunning Frequency Response Analysis

Existing functionality of H3DRES and IMPORT to skip the Frequency Response Analysis is now supported for Random Response-based Fatigue Analysis. With this feature, Frequency Response Analysis does not have to be repeated, if the changes in the model only affect random response or fatigue.

CPYRAM pyramid element

CPYRAM pyramid element type in other software will be read the same as CPYRA.

Resolved Issues

CWELD for Large Displacement Nonlinear Analysis had an issue previously that resulted in non-convergence.
Test data input for reduced polynominal with Hyperelastic material had an issue, if the order of polynomial is less than or equal to 4.
Strain output for CBUSH is corrected for Frequency Response Analysis.
A programming error occured if the model was MPC-based TIE and 2nd order elements.
Offset (ZOFFS in elements or Z0 in composite property) had an issue.
Initial Velocity with TICA for Nonlinear Transient had an issue.
PCOMP(G) for PFBODY was not properly supported.
Wrong Grid point force which is attached to RBE3 in Large Displacement Nonlinear Analysis is now fixed.
Radial Draw direction constraints for topology optimization satisfies manufacturing constraints.
Nonlinear restart run would fail, if the file size went beyond a certain limit.
CFAST with CID=-1 and MFLAG=1 provides results.
The stability and results accuracy of continuum shell (PCOMPLS) improved. In prior versions of OptiStruct, an error message could occur, if the dimension of the model was very small.