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Reference Guide
This manual provides a detailed list and usage information regarding input entries, output entries, and parameters available in OptiStruct.
Output Data
Files Created by OptiStruct
List of output files.
.k.op2 file
The .k.op2 file is a Nastran output2 format file containing the stiffness matrix.

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Overview
OptiStruct is a proven, modern structural solver with comprehensive, accurate and scalable solutions for linear and nonlinear analyses across statics and dynamics, vibrations, acoustics, fatigue, heat transfer, and multiphysics disciplines.
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User Guide
This manual provides detailed information regarding the features, functionality, and simulation methods available in OptiStruct.
Reference Guide
This manual provides a detailed list and usage information regarding input entries, output entries, and parameters available in OptiStruct.
- Input Data
- Output Data
  - Files Created by OptiStruct
    List of output files.
    - .#.#.#.dis file
      The .#.#.#.dis file is a Patran 2.5 ASCII format results file.
    - .#.#.dis file
      The .#.#.dis file is a Patran 2.5 ASCII format results file.
    - .#.#.dis.# file
      The .#.#.dis.# file is a Patran 2.5 ASCII format results file
    - .#.#.els file
      The .#.#.els file is a Patran 2.5 ASCII format results file.
    - .#.#.fat file
      The .#.#.fat file is an ASCII format result file.
    - .#.dis file
      The .#.dis file is a Patran 2.5 ASCII format results file.
    - .#.dis.# file
      The .#.dis.# file is a Patran 2.5 ASCII format results file.
    - .#.eigv file
      The .#.eigv file is an OptiStruct binary data file.
    - .#.els file
      The .#.els file is a Patran 2.5 ASCII format results file.
    - .#.els.# file
      The .#.els.# file is a Patran 2.5 ASCII format results file.
    - .#.grid file
      The .#.grid file is an OptiStruct ASCII format results file.
    - .#.h3d file
      The .#.h3d files are compressed binary files, containing model, analysis, and optimization result data. They can be used to post-process results in HyperView or when using the HyperView Player.
    - .#.mass file
      The .#.mass file is an ASCII format results file.
    - .#.rnf file
      The .#.rnf is an OptiStruct ASCII format results file.
    - .#.sens file
      The .#.sens file is an OptiStruct ASCII format results file.
    - .#.sh file
      The .#.sh file is an OptiStruct ASCII format results file.
    - .#.slk file
      The .slk file is a Microsoft Excel SYLK Format results file.
    - .amls_singularity.cmf file
      The .amls_singularity.cmf file is a HyperMesh command file.
    - .amses_singularity.cmf file
      The .amses_singularity.cmf file is a HyperMesh command file.
    - .bdst file
      The .bdst file is an OptiStruct ASCII format results file.
    - .cmode.csv file
      This file is an output file generated during an Acoustic Complex Eigenvalue Analysis.
    - .cntf file
      An OptiStruct ASCII format results file.
    - .contgap.fem file
      The .contgap.fem file is an ASCII format file. It is used to visualize the internally created contact elements. The contact elements are presented as CGAPG elements.
    - .cpr file
      The .cpr file is an OptiStruct ASCII format results file.
    - .cstr file
      The .cstr file is an OptiStruct ASCII format results file.
    - .dens file
      The .dens file is an OptiStruct ASCII format results file.
    - .desvar file
      The .desvar file is an ASCII format result file.
    - .dis.# file
      The .dis.# file is a Patran 2.5 ASCII format results file.
    - .disp file
      The .disp file is an OptiStruct ASCII format results file.
    - .dvgrid file
      The .dvgrid file is an OptiStruct ASCII format results file.
    - .echo file
      The .echo file is an OptiStruct input file.
    - .effmass file
      The .effmass file is an OptiStruct ASCII format results file.
    - .els.# file
      The .els.# file is a Patran 2.5 ASCII format results file.
    - .flst file
      An OptiStruct XML format file.
    - .flt file
      An OptiStruct ASCII format results file containing the summary of aeroelastic flutter analysis.
    - .force file
      The .force file is an OptiStruct ASCII format results file.
    - .fsthick file
      The .fsthick file is an OptiStruct ASCII format file.
    - .full.mat file
      An OptiStruct ASCII format results file.
    - .gpf file
      The .gpf file is an OptiStruct ASCII format results file.
    - .grid file
      The .grid file is an OptiStruct ASCII format results file.
    - .h3d file
      The .h3d file is a compressed binary file, containing both model and result data. It can be used to post-process results in HyperView or when using the HyperView Player.
    - .h5 file
      A binary file, containing model and result data.
    - .hgdata file
      The .hgdata file is a HyperGraph ASCII results file.
    - .hist file
      The .hist file is an OptiStruct ASCII format results file.
    - .HM.autospc.cmf file
      The .HM.autospc.cmf file is a HyperMesh command file.
    - .HM.comp.tcl file
      The .HM.comp.tcl file is a HyperMesh command file.
    - .HM.conn.tcl file
      The .HM.conn.tcl file is a HyperMesh command file.
    - .HM.crtelem.cmf file
      The .HM.crtelem.cmf file is a HyperMesh command file.
    - .HM.elcheck.cmf file
      The .HM.elcheck.cmf file is a HyperMesh command file.
    - .HM.elcheck.###.cmf file
      The .HM.elcheck_###.cmf file is a HyperMesh command file.
    - .HM.ent.tcl file
      The .HM.ent.tcl file is a HyperMesh command file.
    - .HM.gapstat.cmf file
      The .HM.gapstat.cmf file is a HyperMesh command file.
    - .html file
      The .html file is a HyperText Markup Language file.
    - .interface file
      The .interface file is an ASCII format results file.
    - .joint file
      The .joint file is an ASCII format results file.
    - .k.op2 file
      The .k.op2 file is a Nastran output2 format file containing the stiffness matrix.
    - .kpi file
      An OptiStruct ASCII format results file.
    - .load file
      The .load file is an OptiStruct ASCII format results file.
    - .m.op2 file
      The .m.op2 file is a Nastran output2 format file containing the mass matrix.
    - .mapdsp file
      The .mapdsp file is an OptiStruct ASCII format results file.
    - .mass file
      The .mass file is an OptiStruct ASCII format results file.
    - .mgg file
      The .mgg file is an ASCII format results file.
    - .mnf file
      The .mnf file is an ADAMS modal neutral file.
    - .monitor file
      An OptiStruct ASCII format results file.
    - .monpnt file
      The .monpnt file is an OptiStruct ASCII format results file.
    - .mpcf file
      The .mpcf file is an OptiStruct ASCII format results file.
    - .op2 file
      The .op2 file is a Nastran output2 format for model and results data.
    - .oss file
      The .oss file is an OSSmooth parameter file.
    - .out file
      An ASCII format results file.
    - .pch file
      The .pch file is a Nastran punch format results file.
    - .pcomp file
      The .pcomp file is an ASCII format result file.
    - .peak file
      The .peak file is an ASCII format results file.
    - .pret file
      The .pret file is an OptiStruct ASCII format results file.
    - .prop file
      The .prop file is an OptiStruct ASCII format result file.
    - .rand file
      The .rand file is an OptiStruct ASCII format results file.
    - .reduced.mat file
      An OptiStruct ASCII format results file.
    - .rengy file
      The .rengy file is an ASCII results file.
    - .res file
      The .res file is a HyperMesh binary results file.
    - .secres file
      The .secres file is an OptiStruct ASCII format results file.
    - .seplot file
      The .seplot file is an ASCII format output file.
    - .sh file
      The .sh file is an OptiStruct ASCII format results file.
    - .spcd file
      The .spcd file is an OptiStruct ASCII format results file.
    - .spcf file
      The .spcf file is an OptiStruct ASCII format results file.
    - .stat file
      The .stat file is an ASCII format results file.
    - .strn file
      The .strn file is an ASCII format results file.
    - .strs file
      The .strs file is an OptiStruct ASCII format results file.
    - .trf file
      An ASCII format results file which contains Bulk Data of loads from Aeroelastic Analysis results.
    - .trim file
      An ASCII format results file which contains Aeroelastic Analysis results.
    - _bdst.mvw file
      The _bdst.mvw file is a HyperView session file.
    - _des.h3d file
      A compressed binary file, containing both model and result data. It can be used to post-process results in HyperView or when using the HyperView Player.
    - _e.nlm file
      The _e.nlm file is an OptiStruct ASCII format results file.
    - _e.out file
      An ASCII format results file which can be used for monitoring energy output from nonlinear analysis.
    - _energy.mvw file
      The _energy.mvw file is a HyperGraph session file.
    - _err.grid file
      The _err.grid file is an OptiStruct ASCII format results file.
    - _expl.cntf file
      An OptiStruct ASCII format results file.
    - _fat.#.eqsts file
      An OptiStruct ASCII format results file.
    - _frames.html file
      The _frames.html file is a HyperText Markup Language file.
    - _freq.#.mvw file
      The _freq.#.mvw file is a HyperView session file.
    - _freq.mvw file
      The _freq.mvw file is a HyperView session file.
    - _gauge.h3d file
      A compressed binary file containing both model and result data. It can be used to post-process shell thickness (gauge) sensitivity in HyperView.
    - _gso.slk file
      The _gso.slk file is a Microsoft SLK Data Import format results file.
    - _hist.mvw file
      The _hist.mvw file is a HyperView session file.
    - _impl.h3d file
      A compressed binary file, containing both model and result data. It can be used to post-process results in HyperView or when using the HyperView Player.
    - _ld.monitor file
      The _ld.monitor file is an OptiStruct ASCII format results file.
    - _mass.#.mvw file
      The _mass.#.mvw file is a HyperView session file.
    - _mass.mvw file
      The _mass.mvw file is a HyperView session file.
    - _mbd.h3d file
      A compressed binary file containing both model and result data from a multibody dynamics analysis. It can be used to post-process results in HyperView.
    - _mbd.log file
      The _mbd.log file is an ASCII format .log file from a multibody dynamics analysis.
    - _mbd.mrf file
      The _mbd.mrf file is a Multibody Results File.
    - _mbd.mvw file
      The _mbd.mvw file is a HyperView session file.
    - _mbd.xml file
      The _mbd.xml file is a MotionSolve .xml file from a multibody dynamics analysis.
    - _menu.html file
      The _menu.html file is a HyperText Markup Language file.
    - _modal.#.mvw file
      The _modal.#.mvw file is a HyperView session file.
    - _modal.mvw file
      The _modal.mvw file is a HyperView session file.
    - _nl.h3d file
      A compressed binary file, containing both model and result data. It is output when either NLMON Subcase/Bulk Entry pair or PARAM,NLMON is specified in the input file.
    - _nl.out file
      An ASCII format results file which can be used for monitoring and debugging of nonlinear analysis.
    - _rand.mvw file
      The _rand.mvw file is a HyperView session file.
    - _s#.h3d file
      The _s#.h3d file is a compressed binary file, containing both model and result data. It can be used to post-process results in HyperView or using the HyperView Player.
    - _s#_a.#.frf file
      The _s#_a.#.frf file is an OptiStruct ASCII format results file.
    - _s#_a.frf file
      The _s#_a.frf file is an OptiStruct ASCII format results file.
    - _s#_a.mbd file
      The _s#_a.mbd file is an OptiStruct ASCII format results file.
    - _s#_a.trn file
      The _s#_a.trn file is an OptiStruct ASCII format results file.
    - _s#_d.#.frf file
      The _s#_d.#.frf file is an OptiStruct ASCII format results file.
    - _s#_d.frf file
      The _s#_d.frf file is an OptiStruct ASCII format results file.
    - _s#_d.mbd file
      The _s#_d.mbd file is an OptiStruct ASCII format results file.
    - _s#_d.trn file
      The _s#_d.trn file is an OptiStruct ASCII format results file.
    - _s#_s.trn file
      An OptiStruct ASCII format results file.
    - _s#_v.#.frf file
      The _s#_v.#.frf file is an OptiStruct ASCII format results file.
    - _s#_v.frf file
      The _s#_v.frf file is an OptiStruct ASCII format results file.
    - _s#_v.mbd file
      The _s#_v.mbd file is an OptiStruct ASCII format results file.
    - _s#_v.trn file
      The _s#_v.trn file is an OptiStruct ASCII format results file.
    - _sens.#.mvw file
      The _sens.#.mvw file is a HyperView session file.
    - _shuffling.#.fem file
      The _shuffling.#.fem file is an ASCII format file.
    - _sizing.#.fem file
      The _sizing.#.fem file is an ASCII format file.
    - _sizing.#.inc file
      The _sizing.#.inc file is an ASCII format file.
    - _TH.h5 file
      This is a binary file that contains time history output from Explicit Dynamic Analysis in Hierarchical Data Format, Version 5.
    - _topol.h3d file
      The _topol.h3d file is a compressed binary file containing both model and result data. It can be used to post-process topology (density) sensitivity in HyperView.
    - _tran.mvw file
      The _tran.mvw file is a HyperView session file.
    - <BODY_NAME>.h3d file
      The <BODY_NAME>.h3d file is a compressed binary file from a multibody dynamics analysis that uses flexible bodies defined through a PFBODY Bulk Data Entry.
  - Results Output by OptiStruct
    The tables in this section summarize the results output for different analysis types. They show the formats available for each result and the I/O Option Entry that controls the output of the result.
- Legacy Data
Example Guide
The OptiStruct Example Guide is a collection of solved examples for various solution sequences and optimization types and provides you with examples of the real-world applications and capabilities of OptiStruct.
Verification Problems
This manual presents solved verification models including NAFEMS problems.
Frequently Asked Questions
This section provides quick responses to typical and frequently asked questions regarding OptiStruct.

.k.op2 file

The .k.op2 file is a Nastran output2 format file containing the stiffness matrix.

File Creation

This file is created when PARAM, POST, -5 is present in the Bulk Data section.

File Contents

This file contains the stiffness matrix.