nastran95 0.0.1

Python wrapper for NASTRAN-95 finite element analysis

NASTRAN-95

NASTRAN has been released under the NASA Open Source Agreement version 1.3.

NASTRAN is the NASA Structural Analysis System, a finite element analysis program (FEA) completed in the early 1970's. It was the first of its kind and opened the door to computer-aided engineering. Subsections of a design can be modeled and then larger groupings of these elements can again be modeled. NASTRAN can handle elastic stability analysis, complex eigenvalues for vibration and dynamic stability analysis, dynamic response for transient and steady state loads, and random excitation, and static response to concentrated and distributed loads, thermal expansion, and enforced deformations.

NOTE: There is no technical support available for this software.

Building from Source

Prerequisites

• gfortran (tested with 13.3.0 on Ubuntu 24.04; other versions may work)
• GNU make
• x86-64 Linux (little-endian). Other architectures have not been tested.

On Debian/Ubuntu:

sudo apt install gfortran

Quick Build

The build/ directory contains cleaned, patched source files and a Makefile. To build:

cd build
make

This compiles all Fortran sources (~60 seconds) and links the nastrn executable (~12 MB).

Compiler Flags Explained

Flag	Purpose
-std=legacy	Accept Fortran 77 extensions (Hollerith constants, etc.)
-fno-range-check	Allow integer overflow in constants
-fallow-argument-mismatch	Accept mismatched subroutine argument types
-fallow-invalid-boz	Accept BOZ constants in non-DATA contexts
-fno-automatic	Critical. Use static allocation for local variables so they retain values between calls, as Fortran 66/77 assumed
-w	Suppress warnings (there are thousands)

-fno-automatic is the most important flag. Without it, subroutine-local variables initialized by DATA statements lose their values between calls, causing widespread silent data corruption.

Source Patches

Six source files required changes from the original repository code to compile and run correctly with gfortran. The patched versions live in build/src_*/.

File	Change	Reason
src_mis/endsys.f	Added EXTERNAL LINK	LINK is a gfortran intrinsic; declaration prevents conflict with the NASTRAN subroutine
src_mis/pexit.f	Added EXTERNAL LINK	Same as above
src_mis/sofut.f	Added EXTERNAL RENAME	RENAME is a gfortran intrinsic; declaration prevents conflict
src_mis/xdcode.f	Replaced READ(TEMP,'(80A1)') ICHAR with EQUIVALENCE-based character loop	gfortran's A1 formatted read treats comma as a field separator, breaking rigid format file parsing
src_mds/cputim.f	Rewrote to call ETIME as a function	gfortran provides ETIME as an intrinsic function, not the subroutine the original code expected
src_mds/nastim.f	Same ETIME fix	Same reason
src_mds/dbmdia.f	Changed DATA SCRATCH / 'SCRA','TCHX' / to use 4H Hollerith	CHARACTER literals in DATA for an INTEGER array don't work; Hollerith does
stubs.f	New file with stub subroutines Q8SHPD, T6SHPD, JACOBD	Referenced but not defined in COSMIC/NASTRAN source

Cleaning the Original Sources

The original source files in mis/, mds/, bd/, and bin/ have DOS line endings (CRLF) and sometimes DOS EOF characters (0x1A). The build/src_*/ directories contain cleaned copies with these stripped. If you need to re-clean:

for f in mis/*.f; do
    sed 's/\r//g; s/\x1a//g' "$f" > "build/src_mis/$(basename $f)"
done
# Repeat for mds/, bd/, bin/

The rigid format files in rf/ also need cleaning. Cleaned copies are in rf_clean/.

Running NASTRAN

Environment Variables

NASTRAN reads its configuration from environment variables (not command-line arguments). Input is read from stdin and printed output goes to stdout.

Required variables:

Variable	Description
RFDIR	Path to directory containing rigid format files
DBMEM	Database memory allocation in words (e.g., 12000000)
OCMEM	Open-core memory allocation in words (e.g., 2000000)
DIRCTY	Scratch directory for temporary files
LOGNM	Path for log file output
NPTPNM	Path for new problem tape (checkpoint) file
DICTNM	Path for checkpoint dictionary file
PLTNM	Path for plot file (/dev/null if not needed)
PUNCHNM	Path for punch file (/dev/null if not needed)
OPTPNM	Path for old problem tape (/dev/null for new problems)
SOF1	Substructure operating file 1 (/dev/null if not needed)
SOF2	Substructure operating file 2 (/dev/null if not needed)
FTN11–FTN23	Paths for Fortran scratch units (one file per unit)

Running a Test Case

The simplest way to run a problem:

# Set up environment
export RFDIR=/path/to/nastran/rf_clean
export DBMEM=12000000
export OCMEM=2000000

# Create scratch directory
mkdir -p /tmp/nastran_scratch
export DIRCTY=/tmp/nastran_scratch

# Output files
export LOGNM=/tmp/nastran_scratch/run.log
export NPTPNM=/tmp/nastran_scratch/run.nptp
export DICTNM=/tmp/nastran_scratch/run.dic
export PLTNM=/dev/null
export PUNCHNM=/dev/null
export OPTPNM=/dev/null
export SOF1=/dev/null
export SOF2=/dev/null

# Scratch units
for i in $(seq 11 23); do
    export FTN${i}=/tmp/nastran_scratch/ftn${i}
done

# Run (input on stdin, output on stdout)
./build/nastrn < inp_clean/d01011a.inp > output.out

A helper script test/run_nastran.sh automates this. Usage:

cd test
./run_nastran.sh ../inp_clean/d01011a.inp

Demo Problems

The inp/ directory contains 132 demo problems covering static analysis, normal modes, buckling, frequency response, transient response, and more. Cleaned (no CRLF) copies are in inp_clean/. Reference output is in demoout/. All 132 demo problems run successfully.

Prefix	Rigid Format	Analysis Type
d01xxx	1	Static Analysis
d02xxx	2	Static Analysis with Inertia Relief
d03xxx	3	Normal Modes
d04xxx	4	Differential Stiffness
d05xxx	5	Buckling
d06xxx	6	Piecewise Linear Static
d07xxx	7	Direct Complex Eigenvalues
d08xxx	8	Direct Frequency Response
d09xxx	9	Direct Transient Response
d10xxx	10	Modal Complex Eigenvalues
d11xxx	11	Modal Frequency Response
d12xxx	12	Modal Transient Response
d13xxx	13	Normal Modes with Differential Stiffness

Descriptions of each problem are in the corresponding inp/*.txt files.

Input Format

NASTRAN input is 80-column fixed-format card images. A typical input deck has three sections:

1. Executive Control — selects solution type (SOL), time limit, etc.
2. Case Control — selects loads, constraints, and output requests
3. Bulk Data — defines geometry, elements, materials, loads, and constraints

See the User's Manual text files in um/ for details on each section.

Repository Layout

mis/          Original NASTRAN source — core routines (1674 files)
mds/          Original NASTRAN source — machine-dependent (130 files)
bd/           Original NASTRAN source — block data (40 files)
bin/          Original NASTRAN source — main program (1 file)
build/        Build directory with cleaned/patched sources and object files
  src_mis/    Cleaned + patched MIS sources
  src_mds/    Cleaned + patched MDS sources
  src_bd/     Cleaned block data sources
  src_bin/    Cleaned main program
  stubs.f     Stub subroutines for missing externals
  nastrn      Compiled executable (x86-64 Linux ELF)
  *.COM       Fortran INCLUDE files (COMMON block definitions)
rf/           Rigid format files (original, with CRLF)
rf_clean/     Rigid format files (cleaned)
inp/          Demo problem input decks (132 problems, with CRLF)
inp_clean/    Demo problem input decks (cleaned)
demoout/      Reference output for demo problems
um/           User's Manual text files
test/         Test runner and scratch area
python/       Python modules and tests