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NX Nastran Interface

The strength assessment performed by the software LIMIT® incorporates a static and fatigue module to evaluate your structure. Base material as well as weld analysis can be accomplished using the commercial finite element code NX NASTRAN (Siemens Industry Software Inc).

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Required import files for LIMIT

To allow a fatigue assessment of your structure using NX Nastran, you have to have the .bdf or .dat to access the finite element model and the .op2 with all relevant result data.

Importing the.bdf-file into LIMIT-CAE

  • NX Nastran (.dat; must be ‚long‘- or ‚short‘-Format!)

Coordinate systems


  • Definition in the global coordinate system
  • Definition using CORD1R orCORD2R (RECTANGULAR)

Result data must exist in the global coordinate system (Solids) respectively in the default element coordinate system (shells).

Modifications for OP2-Output

  • sort: SORT1
  • Data format: REAL
  • Yield criteria: VONMISES
  • Position: BILIN (necessary for analyzing the gradient) or CORNER


Note: LIMIT® can average corner values, which is activated with the key *CENTER_STRESS

  • Geometry must be written to .op2-file:                 PARAM, POST, -1
                                                                                       PARAM, OGEOM, YES

Following elements can be analyzed


  • CTETRA (4 nodes) (not suitable for stress assessment)
  • CPENTA (6 nodes) (less suitable for stress assessment)
  • CHEXA (8 nodes) (less suitable for stress assessment)
  • CTETRA (10 nodes) => stress gradient available
  • CPENTA (15 nodes) => stress gradient available
  • CHEXA (20 nodes) => stress gradient available


  • CQUAD4
  • CQUAD8
  • CTRIA3
  • CTRIA6


For detailed information please refer to the NX Nastran interface document (.pdf) or contact our LIMIT® support.