NASTRAN-G(1)

NAME

nastran-g - convert a NASTRAN finite element model to a BRL-CAD database

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SYNOPSIS
DESCRIPTION
OPTIONS
EXAMPLES
SEE ALSO
AUTHOR
COPYRIGHT
BUG REPORTS

SYNOPSIS

nastran-g [-n] [-m] [-t _tolerance_] [-x _lvl_] [-X _lvl_] [-i _nastran_file_] -o _database.g_

nastran-g reads a NASTRAN bulk data deck and converts the geometry it describes into a BRL-CAD database.g file. Input is read from the file named with -i, or from standard input if -i is not given. Conversion begins at the BEGIN BULK card; everything before it is ignored.

Only a subset of NASTRAN element types is handled: CROD and CBAR elements become right circular cylinders (RCC) whose radius is derived from the referenced PBAR cross-sectional area, while CTRIA3 and CQUAD4 shell elements are tessellated into surfaces. Grid points (GRID), coordinate systems (CORD1/CORD2), and properties (PBAR, PSHELL, BAROR) are interpreted as needed. All geometry is transformed into the default Cartesian coordinate system. The resulting primitives are grouped into combinations (pbars, shells, and a top-level all).

By default the shell elements are written as bot(5) (BOT) solids and the model is assumed to be in inches.

OPTIONS

-n: Write surfaces created from CQUAD4 and CTRIA3 elements as NMG solids rather than as the default BOT solids.
-m: Treat the NASTRAN input as millimeters rather than the default inches.
-t tolerance: Set the distance tolerance, in millimeters: two vertices closer than this are treated as the same vertex. Defaults to the BRL-CAD distance tolerance.
-x lvl: Set the librt debug flags to the given hexadecimal value.
-X lvl: Set the NMG debug flags to the given hexadecimal value.
-i nastran_file: Read the NASTRAN bulk data deck from nastran_file instead of standard input.
-o database.g: Write the converted geometry to database.g. Defaults to nastran.g.

EXAMPLES

Example 1. Convert a metric model and inspect the result

nastran-g -m -i wing.nas -o wing.g
mged wing.g 'tops'

Converts the millimeter NASTRAN deck wing.nas to wing.g, then lists the top-level objects with mged(1) so the all combination can be drawn and examined.

Example 2. Convert from a pipeline using NMG shells and a tightened tolerance

cat model.bdf | nastran-g -n -t 0.005 -o model.g

Reads the bulk data deck from standard input, writes shell elements as NMG solids, and treats vertices within 0.005 mm of each other as coincident.