Altair OptiStruct 2022.3 Release Notes

Highlights

Two-dimensional Plane Stress Elements
New fastener elements with CFASTG
Heat flux and Current output at model cross-sections
Thickness gradient constraints for Free-size Optimization

New Features

Stiffness, Strength and Stability

Parameters for debugging of Nonlinear Analysis

There is a new set of parameters introduced, known as NLDEBUG parameters which helps with debugging of nonlinear analysis by simplifying certain aspects of the model. The following parameters are now available:

NLDEBUG,RMNLMAT: Setting this parameter will ignore nonlinear materials specified in the model. Typically, certain nonlinear materials are completely ignored while other nonlinear materials are linearized.
NLDEBUG,NLP2NLC: Setting this parameter will convert NLPARM-based setup to an NLCTRL-based setup in a nonlinear model. When NLPARM (and additionally NLADAPT, if any) entries are defined in nonlinear models, then they are converted internally to NLCTRL.
NLDEBUG,CONT2TIE: Setting this parameter in a model which contains contact will convert any non-FREEZE contact internally to FREEZE contact.; Refer to the OptiStruct 2022.3 documentation for more details on NLDEBUG parameters.

Plane Stress

The two-dimensional plane stress elements are now available. The quadrilateral and triangular plane stress elements are CQPSTS and CTPSTS, respectively (both are applicable to first order and second order elements). Plane stress elements reference PPLANE as property and all elements should be defined either in x-y plane or in x-z plane. Plane stress elements can be used for linear static analysis, nonlinear static analysis with both SMDISP and LGDISP options, transient and frequency response analysis, real and complex eigenvalue analysis. Currently they do not support inertia relief analysis, buckling analysis, heat transfer analysis and optimization. The currently supported materials are MAT1, MATS1 and MAT2.

Ductile Damage

Ductile damage initiation based on plastic strain has been added. This is supported for solids in both small displacement and large displacement nonlinear analysis. It is also supported for shells, for small displacement nonlinear analysis only. DAMAGE continuation line has now been added in MATS1 entry (elasto-plasticity). DAMAGE continuation line refers to DMGINI (damage initiation) and DMGEVO (damage evolution) Bulk Data Entries.

New JOINTG output requests

Two new JOINTG output requests are now available:

JOINTD I/O Entry is available for JOINTG displacement output.
JOINTF I/O Entry is available for the following JOINTG output:
- JOINTG Forces
- JOINTG Reaction Forces
- JOINTG Viscous Forces (available if PROPERTY on PJOINTG is DAMP)
- JOINTG Stop and Lock Status

JOINTF is turned on by default for linear/nonlinear static analysis and explicit analysis.

JOINTD is not currently the default for any analysis type.

JOINTD and JOINTF output are available in .h3d, _impl.h3d, _expl.h3d, and .joint files.

"SLIP history" contact output

The CONTF(SLIPPED,OPTI) option can be used to activate output of whether a frictional contact interface has experienced slipping status up to the current increment in an implicit nonlinear analysis.

Change in PARAM,KSMNL4PL Default

The default of PARAM,KSMNL4PL has been changed from 0 to 1.

Adiabatic Analysis

Adiabatic analysis is now available in OptiStruct. It is a coupled thermal-structural analysis, which is applicable in modeling systems with inelastic strain which can lead to quick heating of the material, without sufficient time for the heat to be transmitted. The heat transfer and structure analysis are coupled at each time step.

An ADIABATIC Subcase Entry should be specified in an implicit nonlinear subcase to activate adiabatic analysis.
It is currently supported for both Nonlinear static and Nonlinear transient analysis (SMDISP and LGDISP)
Three-dimensional elements and Axisymmetric elements are currently supported.
Some parts of the model are made of elastic material, and other parts are inelastic.
Elasto-plasticity (MATS1), Visco-elasticity (MATVE), Cohesive elements (MCOHE, MCOHED) are supported for defining inelastic materials for adiabatic analysis.
Cohesive elements only work as a heat source. Heat conduction or specific heat effect are not considered for cohesive elements.
All the elements in a model participate in the structural analysis, but only the elements with thermal material participate in thermal analysis.
Results for adiabatic analysis are available, such as Grid temperature, Temperature gradient, Heat flux, Element heat energy, incremental heat power density, total heat power density, and so on.

Explicit Dynamic Analysis

JOINTG results in time history output (THIST): The results include JOINTG force, reaction force, viscous force and STOP/LOCK status in time-history output for explicit analysis.
Cohesive Elements: The constitutive response of cohesive elements using a traction-separation description by using MCOHED (in order to define the damage initiation and damage evolution), or define the constitutive response of cohesive elements using a continuum approach by referencing isotropic material (MAT1) or elasto-plasticity material (MATS1). This is now supported for explicit analysis.
Nodal mass change output: Nodal mass change due to mass scaling is available in .h3d file. This is the delta mass (identifies how much mass is added).
New failure type in MATF as maximum plastic strain: A New failure type is now available in MATF, which can be activated by setting CRITERIA field to PLAS. This activates the maximum plastic strain failure criterion. The V1 field on MATF defines the maximum plastic strain value for the failure calculation.

Electrical Analysis

Pressure and clearance dependent resistivity in PCONTEC

Pressure and Clearance-dependent resistivity can now be defined on PCONTEC entry for electrical analysis. The TPID field is available to point to a TABLED# entry that specifies resistance per unit contact area, based on contact pressure. The TCID field points to a TABLED# entry that specifies resistance per unit contact area, based on contact clearance. TPID can be specified together with TCID.

Refer to the PCONTEC documentation for more information.

Sequential coupling of structural, electrical analysis, and heat transfer analysis

Structural, electrical, and heat transfer analyses can now be sequentially coupled in OptiStruct. The following subcases are currently supported for this implementation:

Structural analysis

Implicit Nonlinear Static Large Displacement Analysis

Heat Transfer analysis

Linear or Nonlinear Steady-State Heat Transfer
Linear Transient Heat Transfer

Electrical analysis

Steady-State Electrical analysis
Multi-Steady Electrical analysis

All three analyses are defined in the model. The structural analysis subcase should be referenced by both the electrical and heat transfer subcases via STATSUB(STRUCTURE). The heat transfer subcase should reference the electrical analysis subcase via the JOULE entry. The solution coupling process depends on the type of defined subcases, but generally, the structural analysis will be solved first. There will be no influence of heat transfer and electrical subcases on the structural subcase. The deformed mesh from the structural subcase, sequentially is used to update the conduction or convection characteristics of heat transfer (electrical or heat subcase), and the corresponding loading, such as QVOL or QBDY1, and subsequently contact (which also influences TPID and TCID in PCONTEC).

Current flow output across sections

Current flow output across sections of the model is now available via the RESULTANT I/O Entry. The sections in the model for which output is requested should be defined via the SECTION Bulk Data Entry, with the STYPE field set to ELEC. The presence of SECTION entry is sufficient for Current flow output in Steady-State Electrical analysis (RESULTANT is default). For Multi-Steady Electrical Analysis, both SECTION entry and the RESULTANT entry are required for Current flow output. Current flow results are output in H3D and .secres files.

Noise and Vibration

Performance enhancement of MATFi materials: The performance of frequency-dependent materials (MATFi) has been enhanced. Especially enhancements that have been applied in identifying material data where properties do not change over certain loading frequencies.
Steady-state analysis for Vibration solutions: Steady-state analysis is now available for Vibration solutions to convert results of frequency-response analysis from frequency domain to time domain and also optionally combine the results with results from static subcases and other frequency-response subcases in the time domain. Currently, displacement, velocity, acceleration, stress and strain are supported.; A new subcase type, ANALYSIS STEADY is now available for Steady-state analysis. The STEADY Subcase Information Entry is available and should point to the new STEADY Bulk Data Entry, to activate steady-state analysis. The STEADY Bulk Data Entry provides options to control the combination of frequency response and linear static subcases used for steady-state analysis.; The IMPORT I/O Entry can be used in the corresponding FRF and linear static subcases to run steady-state analysis directly from H3D files. All corresponding subcases should contain the IMPORT I/O Entry in such a situation.

Rotor Dynamics

Order-based FRF analysis for rotor dynamics

The SYNCFAC field is now available on the RGYRO Bulk Data Entry to specify the scaling factor used for rotating speed in order-based frequency response analysis for rotor dynamics. This scaling factor is applied to the rotating speed of the reference rotor to determine the rotating speed of a rotor.(1)

ω = S Y N C F A C \cdot Ω_{r e f}

Where,

$ω$: Whirling frequency (Hz).
$Ω_{r e f}$: Speed of the reference motor (Hz).

Fatigue Analysis

Superimpose stress from transient analyses with stress from static subcases

A single FATEVNT entry can now combine the transient analysis results and the static subcase results via FATLOAD with user-defined scaling factor.

See an example below. FATLOAD 611 and

FATLOAD
                                612

reference static subcases while

FATLOAD
                                601

and FATLOAD 44 reference transient subcases.

FATSEQ       401
+            501       1     911       2
FATEVNT      501     601     611      44     612
FATEVNT      911     611      44
FATLOAD      601              11   
FATLOAD       44              15   
FATLOAD      611             109   0.5      
FATLOAD      612             119   0.500

Heat Transfer Analysis

Heat Flow output across sections: Heat flow output across sections of the model is now available via the RESULTANT I/O Entry. The sections in the model for which output is requested should be defined via the SECTION Bulk Data Entry, with the STYPE field set to HEAT. The presence of SECTION entry is sufficient for Heat flow output in Linear and Nonlinear Steady-State Heat Transfer analysis (RESULTANT is default). For Linear and Nonlinear Transient Heat Transfer Analysis, both SECTION entry and the RESULTANT entry are required for Heat flow output. Heat flow results are output in H3D and .secres files.

Optimization

LEVELSET optimization requires reduced number of iterations: LEVELSET optimization has been enhanced to require a reduced number of iterations to converge, while simultaneously maintaining solution robustness and accuracy.
Thickness gradient with Free-size optimization: Thickness gradient constraints are now available with free-size optimization. This can be defined via the DRAW continuation line on the DSIZE Bulk Data Entry. Two options are available for defining the draft angle type: FIXED and MINIMUM. The FIXED option fixes the draft angle, while the MINIMUM option activates the variable draft angle option. The Thickness gradient direction is defined via the DAID and DFID fields, and the draft angle is defined via the ANGLE field.
Element SET based design space for topology and free-size optimization: The design space for Topology and Free-size optimization can now be defined via element SETs. This is defined by setting the PTYPE field on DSIZE or DTPL entries to SET. Then the PID# fields can reference the corresponding element SET IDs. Depending on whether DTPL or DSIZE is used, the element SET can be a set of solid or shell elements. Multi-material, levelset, and lattice optimization are currently not supported.; Refer to the DTPL and DSIZE documentation for more information.

General

Power flow output for Transient Analysis: Power flow output, via the POWERFLOW I/O Entry, is now supported for Direct and Modal Transient Response Analysis. It was already supported for Direct and Modal Frequency Response Analysis in previous releases.
SET of grids support for ASET/BSET/CSET, BNDFIX/BNDFIX1 and BNDFREE/BNDFREE1: The grids to be defined as part of the entries ASET/BSET/CSET, BNDFIX/BNDFIX1 and BNDFREE/BNDFREE1, can now also be defined as grid SETs. This is available by setting the GSET flag on the corresponding entry, leading to the IDs being considered as grid SETs instead of individual grids.
MASSSET: MASSSET can be used to define subcase-dependent mass using the MASSSET Subcase Information and MASSSET Bulk Data Entries. The masses can be defined as mass sections via the BEGIN,MASSID entries. These sections have their own IDs and these IDs can be referenced (for scaling and linear combination) on the MASSSET Bulk Data Entry. The MASSSET Bulk Data Entry is then referenced in a subcase by the MASSSET Subcase Information Entry.
SHIFTY for TLOAD2: The load amplitude (Y) on the TLOAD2 entry can be shifted using the SHIFTY field on the TLOAD2 Bulk Data Entry. A real value should be specified on the SHIFTY field to apply a shift to the load amplitude. This is currently supported for direct and modal linear transient analysis.

Resolved Issues

The results in HyperView no longer show NA when the corner option is turned on for factor of safety output with 2nd order elements.
You can no longer apply zero loading may be applied when the cylindrical system is used for gravity loading.
Topology optimization results have been corrected for transient analysis with material damping.
NODMIG option now works as expected for GROUNDCHECK.
Odd results with Level set optimization are no longer observed when the draw direction constraints are used.
Corrected the insufficient memory available issue for Simpack recovery run.
Acceleration loading (ACCEL,ACCEL1,ACCEL2) defined in local part is now handled as expected when used in parts-instances with the ROTATE option.
A programing error no longer occurs when ERP participation is requested and there are fluid elements in the model.
A high enough stiffness is used for rotational dofs with penalty-based RIGID option in PBUSH to resolve issues with low stiffness.
Contribution from contact in GPFORCE are corrected so they are no longer constant for each time increment in nonlinear analysis.
Homogenized shell stress for composite models in large displacement nonlinear analysis.
Gravity loading with cylindrical coordinate system defined no longer produces zero force.
Kinetic frictional force output is now correct for continuous sliding contact (CONSLI).
MPC force in .op2 file from large displacement nonlinear analysis is now correct.