9.3.3. Input File Format (ANSYS & NASTRAN)

The FFlex body of RecurDyn at the minimum requires the definition of nodes and element and their connections. If the property and material data do not exist, RecurDyn/FFlex automatically generates the default properties and materials based on the connection information

How to make an input file

The NASTRAN input is a file that contains FE information to analyze the system. RecurDyn extracts the necessary information from this file.

The ANSYS input file is an exported file from ANSYS using the CDWRITE command and the input file has an extension cdb.

  • CDWRITE Command Form (CDWRITE, Option, Fname, Ext, -- , Fnamei, Exti, Fmat )

    • Option: Selects the data to write (ALL, COMB, DB, SOLID….).

    • Fname: File name and directory path. An unspecified directory path defaults to the working directory.

    • Ext: File name extension. If Fname is blank, the extension defaults to ‘*. cdb'.

    • --: Unused field

    • Fnamei: The name of IGES file which contains parts or assemblies is supported by the mechanical application and its directory path.

    • Exti: File name extension. The extension defaults to IGES.

    • Fmat: Format of the output file (It defaults to BLOCKED)

      • BLOCKED: The Output is read faster more in this format.

      • UNBLOCKED

Caution

  • RecurDyn/FFlex recommends the user does not use additional command parameters.

  • When you use the CDWRITE command with additional command parameters, Fmat of additional command parameters must be BLOCKED to import the *.cdb file.

  • For more information about the CDWRITE command, refer to the ANSYS manual.

Supported Nastran Command

Nastran input file (*.dat / *.bdf) can be imported to RecurDyn. However, RecurDyn does not support parts of all command. Table 9.2 shows supported commands.

Table 9.2 Supported Command list

Type

Commands

Node

GRID

Element

BEAM

CBEAM

SHELL

CTRIA3 CTRIA6 CQUAD4 CQUAD8

SOLID

CTETRA CPENTA CHEXA CPYRAM

MASS

CONM2

RIGID

RBE2, RBE3

Property

PBEAM PBEAML PSHELL PSOLID

Material

MAT1 MAT2 MAT8

Coordinate

CORD1C CORD1R CORD1S

CORD2C CORD2R CORD2S

B.C.

SPC SPC1

Set

SET

Note

  • If the SET is used, Grid ID and Element ID must have unique ID.

  • RecurDyn does not support stress output option field and related fields.

  • RecurDyn only supports interpolation element type of ‘Rotation & Translation’. So, REFC field of RBE3 is converted to ‘123456’. User cannot control this value in GUI.

  • RecurDyn only supports ‘1’ as weighting factor. So, WTi field of RBE3 is converted to ‘1’. User cannot control this value in GUI.

  • RecurDyn only supports translation degree of freedom in the case of independent nodes. So, Ci field of RBE3 is converted to ‘123’. User cannot control this value in GUI.

Supported Elements

Some kinds of structural elements are imported. Refer to Table 9.3.

Table 9.3 Supported element list

Type

RecurDyn/FFlex

NASTRAN

ANSYS

1D Element

Beam 2

CBEAM

Beam 4

Beam 188

2D Element

Shell 3

CTRIA 3

CTRIA 6

Shell 63

Shell 93

Shell 181

Shell 4

QUAD 4

Shell 63

Shell 181

Shell 9

QUAD 8

Shell 93

3D Element

Solid 4

CTETRA

Solid45

Solid185

Solid 5

CPYRAM

Solid95

Solid185

Solid186

Solid 6

CPENTA

Solid45

Solid95

Solid185

Solid186

Solid 8

CHEXA

Solid 45

Solid 185

Solid 10

CTETRA

Solid 92

Solid95

Solid186

Solid187

Solid 26

CHEXA

Solid 95

Solid 186

Rigid Element

Rigid Element

RBE2, RBE3

Rigid Region

Mass Element

Mass Element

CONM2

Mass 21

Supported Materials and Properties

Table 9.4 Supported material and property list

Type

RecurDyn/FFlex

NASTRAN

ANSYS

1D Element

PBEAM

PBEAM

PBEAML

Real Constant

SECTYPE, SECDATA

2D Element

PSHELL

PSHELL

Real Constant

SECTYPE, SECDATA

3D Element

PSOLID

PSOLID

NONE

Material

Isotropic

Orthotropic2D

Anistropic2D

Plastic

MAT1

MAT2

MAT8

Material

Supported Boundary/Set Type

Table 9.5 Supported Boundary/Set Type

Type

RecurDyn /FFlex

NASTRAN

ANSYS

Boundary

BC

SPC

Displacement

Constraint

SPC1

Set

SET

SET

Component

Caution

  • In the 2D element, the parabolic triangular type that has 6 nodes are converted to linear element

  • In the 3D element, the parabolic pentagonal type that has 6 nodes are converted to a linear element.

  • In ANSYS, the constraint equation is converted to a rigid element where the base node is treated as a primary node.

  • The Pyramid type elements are divided into two tetrahedral elements.

  • During the SET data converting, corresponding patch sets that include some or partial entities are automatically generated.