Exporting the Finite Element Model

For information on exporting an Exodus File, see Exporting Exodus II Files. Custom translators are available to translate between the Exodus II format and a limited number of other analysis code formats. Contact the Trelis development team for a current list of supported translator formats. The general syntax for the various exporters is as follows. The specific exporter commands are listed below.

Export {Abaqus [Explicit]* [Partial]* | Nastran | Ideas | Patran | LSDyna | Fluent} <’filename’> [Block <id_list>] [Sideset <id_list>] [Nodeset <id_list>] [BCSet <id_list>] [dimension {2|3}***] [Overwrite]  [Everything] [NX]**

Export VRML <'filename'> [Overwrite]

* Explicit and Partial keywords only available with Abaqus Exporter

** NX keyword only available with I-DEAS Exporter

***The dimension argument is also optional. Most element types have an inherent dimensionality associated with them. For example, a truss or beam element is inherently 2D while a hex or tetra element is 3D. Without this argument, only the x-y location of the nodal coordinates of 2D elements are written to the Exodus II file. Using the argument dimension 3, in this example, permits the full 3D coordinates to be written.

The Abaqus Exporter has a few additional keywords available. See the last paragraph below for an explanation of those keywords:

Export Abaqus <'filename'> [Block <id_list>] [Sideset <id_list>] [Nodeset <id_list>] [BCSet <id_list>] [dimension {2|3}] [nodefile <'filename'>] [elementfile <'filename'>] [flatfile] [overwrite] [everything]

If no blocks are exported, Trelis will export all nodes and elements in the model. If one or more blocks are entered in the command, only those blocks will be exported. Similarly, if no BCSets are entered in the command, Trelis will export all boundary conditions as a single BCSet. If one or more BCSets are entered into the command, only those BCSets will be exported. Use the overwrite flag to overwrite an existing file.

By default, Trelis will reassign node and element IDs based on which block they are in. If the everything keyword is present, Trelis will export all nodes and elements in the model, whether they are in a block or not.

The I-DEAS Universal file can be read into Siemen’s NX application if the file is generated using the NX keyword. This is because extra information must be written to an I-DEAS Universal file in order for NX to be able to read it.

There are a few keywords specifically for the Abaqus exporter. Flatfile can be used if the user desires Trelis to write out the model as a "flat file." Abaqus refers to files a "flat files" when they do not use the *PART/*INSTANCE structure. All nodes and elements will be defined at the global level. The keywords elementfile and nodefile can be used to instruct Trelis to export the nodes and/or elements to a separate file.

If the Explicit keyword is used with Abaqus, Trelis will write an Abaqus Explicit deck. The one Explicit-only feature that Trelis supports is Fixed Mass Scaling.

If the Partial keyword is used with Abaqus, Trelis will write a partial Abaqus deck. Trelis will output the mesh as defined by the Abaqus keywords PART, NODE, ELEMENT, NSET, ELSET, and SURFACE. Everything else is ignored. Use the Abaqus keyword INCLUDE to include this file in a master Abaqus deck for analysis.

Specific Exporter Commands:

Export Abaqus [explicit] '<filename>' [Block <id_list>] [Sideset <id_list>]    [Nodeset <id_list>] [BCSet <id_list>] [group <id_list>]  [instance block <id_list> [source_csys <id_list>] target_csys <id_list> [preview]] [dimension {2|3}] [overwrite]  [everything] [partial]

Set Abaqus Precision <n=6>

Note: This command can be used to control the number of decimal places written to the Abaqus file.

Export Nastran '<filename>' [Block <id_list>] [Sideset <id_list>]  [Nodeset <id_list>] [BCSet <id_list>] [dimension {2|3}] [overwrite]  [everything]]

Export Ideas '<filename>' [NX] [Block <id_list>] [Sideset <id_list>]    [Nodeset <id_list>] [BCSet <id_list>] [dimension {2|3}] [overwrite]  [everything]

Export Patran '<filename>' [Block <id_list>] [Sideset <id_list>]    [Nodeset <id_list>] [BCSet <id_list>] [overwrite] [everything][dimension {2|3}]

Export Lsdyna '<filename>' [Block <id_list>] [Sideset <id_list>]    [Nodeset <id_list>] [BCSet <id_list>] [overwrite]

Export VRML <'filename'> [Overwrite]

Export Fluent '<filename>' [Block <id_list>] [Sideset <id_list>]    [Nodeset <id_list>] [BCSet <id_list>] [dimension {2|3}] [overwrite] [everything]

Note: The following command is for exporting mesh geometry, (.msh format.)

Export Fluent '<filename>' [Surface <id_list>|Volume <id_list>] [Overwrite]

Additional Information on building models for CFD

Instancing parts with ABAQUS

Defining PARAMS for NASTRAN

Supported element types

Trelis Element Type ExodusII Abaqus Nastran I-DEAS UNV Patran LS-DYNA Fluent
Sphere SPHERE         ELEMENT_SPH  
Spring SPRING SPRINGA/SPRING1/SPRING2 CBUSH1D**        
Bar BAR B21** CROD** 121** Bar2    
Bar2 BAR2 B21** CROD** 121** Bar2    
Bar3 BAR3 B22** CROD** 121**      
Beam BEAM B31 CROD** 21** Bar2 ELEMENT_BEAM  
Beam2 BEAM2 B31 CROD** 21** Bar2 ELEMENT_BEAM  
Beam3 BEAM3 B32 CROD** 24**      
Truss TRUSS T3D2/T3D2T*,** CROD** 121** Bar2 ELEMENT_BEAM  
Truss2 TRUSS2 T3D2/T3D2T*,** CROD** 121** Bar2 ELEMENT_BEAM  
Truss3 TRUSS3 T3D2/T3D2T*,** CROD** 121**      
Quad QUAD CPE4R/CPE4RT* CQUAD4 54 Quad4 ELEMENT_SHELL 3
Quad4 QUAD4 CPE4R/CPE4RT* CQUAD4 54 Quad4 ELEMENT_SHELL 3
Quad5 QUAD5       Quad5    
Quad8 QUAD8 CPE8R/CPE8RT* CQUAD8 55 Quad8    
Quad9 QUAD9 S9R5 CQUAD 55 Quad9    
Shell SHELL S4R/S4RT* CQUAD4 94*** Quad4 ELEMENT_SHELL  
Shell4 SHELL4 S4R/S4RT* CQUAD4 94*** Quad4 ELEMENT_SHELL  
Shell8 SHELL8 S8R/S8RT* CQUAD8 95*** Quad8    
Shell9 SHELL9 S9R5   95*** Quad9    
Tri TRI CPS3/CPS3T* CTRIA3 51 Tri3 ELEMENT_SHELL 1
Tri3 TRI3 CPS3/CPS3T* CTRIA3 51 Tri3 ELEMENT_SHELL 1
Tri6 TRI6 CPS6/CPS6T* CTRIA6 52 Tri6    
Tri7 TRI7     52 Tri7    
Trishell TRISHELL STRI3 CTRIA3 91 Tri3 ELEMENT_SHELL  
Trishell3 TRISHELL3 STRI3 CTRIA3 91 Tri3 ELEMENT_SHELL  
Trishell6 TRISHELL6 STRI65 CTRI6 92 Tri6    
Trishell7 TRISHELL7     92 Tri7    
Hex HEX C3D8R/C3D8RT* CHEXA 115 Hex8 ELEMENT_SOLID 4
Hex8 HEX8 C3D8R/C3D8RT* CHEXA 115 Hex8 ELEMENT_SOLID 4
Hex9 HEX9            
Hex20 HEX20 C3D20R/C3D20RT* CHEXA 116 Hex20    
Hex27 HEX27   CHEXA        
Tetra TETRA C3D4/C3D4T* CTETRA 111 Tet4 ELEMENT_SOLID 2
Tetra4 TETRA4 C3D4/C3D4T* CTETRA 111 Tet4 ELEMENT_SOLID 2
Tetra8 TETRA8            
Tetra10 TETRA10 C3D10/C3D10MT* CTETRA 118 Tet10 ELEMENT_SOLID  
Tetra14 TETRA14            
Wedge WEDGE C3D6/C3D6T* CPENTA 112  

ELEMENT_SOLID

6
Hexshell HEXSHELL            
Pyramid

PYRAMID

 

CPYRAM

115^

     
Pyramid5 PYRAMID5  

CPYRAM

115^      
Pyramid8 PYRAMID8  

CPYRAM

116^      
Pyramid13 PYRAMID13  

CPYRAM

116^      
Pyramid18 PYRAMID18  

CPYRAM

116^      

*Thermal element

**Check to make sure the element's properties are correct after exporting

***Also exports lofting factor for shell elements (IDEAS)

^ The element type will be HEX but the number of nodes will be the number of nodes in the pyramid

Supported boundary conditions types

Trelis Element Type ExodusII Abaqus Nastran I-DEAS UNV Patran LS-DYNA Fluent
BC Set   *STEP SUBCASE 2428      
Displacement   *BOUNDARY SPC 791 08    
Temperature   *BOUNDARY TEMP 791 10    
Force   *CLOAD FORCE/MOMENT 790 07    
Pressure   *DSLOAD PLOAD4 790 6    
Convection   *SFILM *** CONV 790 17    
Heat Flux   *DSFLUX QHBDY 790 16    
Contact   *CONTACT   2471      
Materials  

*MATERIAL

MAT1_, MAT4_

1716

03

   
CFD Boundary Conditions              
Interior             2
Wall             3
Inlet Pressure             4
Inlet Massflow             20
Inlet Velocity             10
Outlet Pressure             5
Far-field Pressure             9
Symmetry             7

*** Does not allow separate temperatures for top and bottom of shell elements. Values will be averaged.