OpenRadioss / Radioss starter deck (*_0000.rad)

The input deck of the OpenRadioss explicit solver (and of Altair Radioss) in its native "block format": the starter file, <run>_0000.rad. Engine files (_0001.rad, run control) are refused. OpenRadioss also reads LS-DYNA .k decks natively, which meshio++ reads as lsdyna.

Format name	radioss
Extensions	.rad (also recognised by content: #RADIOSS STARTER, or /BEGIN as the first non-comment line)
Read / Write	✓ / —
Extra dependencies	—

Reading

import meshioplusplus

mesh = meshioplusplus.read("crash_0000.rad")

read takes no options. Both engines (the C++ core and the pure-Python reference) read the same meshes.

The deck

• #RADIOSS STARTER, /BEGIN (run name, input version, units), then /KEYWORD/option/id blocks up to /END; anything after /END is ignored.
• Lines starting with # or $ are comments; #include file inlines another file (relative to the including one, at most 8 deep, ended early by #enddata); a missing include is a warning.
• Fields are 10 columns wide for integers and 20 for reals from input version 51 on, 8 and 16 before; a line containing a comma is split on commas instead. The version is field_data["radioss:version"].
• A keyword's id is its first integer field: /BOX/RECTA/3/1 is box 3 given in unit system 1 (the unit system itself is not applied), /SURF/PART/EXT/12 is surface 12.
• Units (v16.11.0): /BEGIN's input and work units (mass, length and time, 20 columns each) set the length scale. Radioss runs in the work units, so coordinates and box dimensions are multiplied by input length ÷ work length, and the factor is field_data["radioss:length_scale"] when it is not 1. A length unit is an SI prefix and m (mm, mum, km…), in, ft, yd, mi or a number of metres; an unknown one leaves lengths as written, with a warning.

Card	meshio++ type
/NODE	points
/BRICK/part	hexahedron, or the tetrahedron, pyramid or wedge a brick with repeated nodes stands for (1 2 3 3 4 4 4 4, 1 2 3 4 5 5 5 5, 1 2 3 3 5 6 7 7, 1 2 3 1 5 6 7 5, …)
/PENTA6/part	wedge
/TETRA4/part / /TETRA10/part	tetra / tetra10
/BRIC20/part	hexahedron20; with a zero mid-edge node, its corners as a hexahedron (with a warning)
/SHELL/part	quad, or triangle when its last two nodes coincide
/SH3N/part, /QUAD/part, /TRIA/part	triangle, quad, triangle
/BEAM/part, /TRUSS/part, /SPRING/part	line (the beam's orientation node is dropped; a single-node spring is skipped)
/TSHELL, /SHEL16, /SPHCEL, /RIVET, /XELEM	skipped, with one warning naming them

The part id is the keyword's last field. Every cell's part, and the property and material its /PART names, are the radioss:part, radioss:property and radioss:material cell data.

A /TETRA4 or /TETRA10 written with the mirrored winding is reoriented, with a warning: OpenRadioss's own QA deck INT_25 has every tetrahedron that way, while gmsh writes them positive.

Node order

/BRIC20 lists the bottom ring of mid-edge nodes, then the vertical ones, then the top ring, so it uses the "radioss" table of the node-ordering registry (gmsh's getVertexRAD). /TETRA10 and the other cards are in meshio++'s order.

Regions

Card	Region
/PART/id	a cell region named by its title (else Part <id>), tag = part id; parts with no elements are kept, empty
/SUBSET/id	a cell region of the parts that name this subset or one below it
/GRNOD/<sub>/id	a point region
/GRBRIC, /GRSHEL, /GRSH3N, /GRQUAD, /GRTRIA, /GRBEAM, /GRTRUS, /GRSPRI	a cell region
/SURF/SEG/id	a side region: each segment's facet (a shell segment is the shell's own face, as in LS-DYNA; a 2-node segment in a 2-D deck is a cell edge)
/SURF/PART, /SUBSET, /MAT, /PROP (v16.11.0)	the shells' own faces of those parts; with /EXT also the solids' faces no other of those solids shares, with /ALL every solid face
/SURF/GRBRIC/EXT, /FREE (v16.11.0)	the brick group's faces no other brick of the group shares (EXT), or no other solid of the model (FREE)
/SURF/GRSHEL, /GRSH3N, /GRTRIA (v16.11.0)	the group's own faces
/SURF/SURF (v16.11.0)	the union of other surfaces; a negative id removes one

A group's <sub> may be:

• the entity itself (/GRBRIC/BRIC, ids; a negative id removes one), PART (the parts' cells of that family, or their nodes for GRNOD), SUBSET, another group of the same keyword, and for GRNOD an element group or a /SURF/SEG surface;
• GENE (v16.11.0): pairs of first and last ids, every entity whose id falls in one; GEN_INCR: triples of first, last and step;
• BOX and BOX2 (v16.11.0): box ids (a negative one removed). A node is taken when it lies inside the box; an element, under BOX when all its nodes do, under BOX2 when any does, as the starter decides.

Boxes are /BOX/RECTA (the corners, from two nodes or coordinates), /BOX/CYLIN (the axis ends and a diameter), /BOX/SPHER (the centre and a diameter), and /BOX/BOX (other boxes; a negative id subtracts one). A box with a skew system contains nothing, with a warning. Other generators are not resolved: the region is written empty with a warning. Every region is named by its title line (else <KEYWORD>_<id>), tag = its id; a name already taken gets [KEYWORD] appended.

Materials, properties, loads, contacts, rigid bodies and every other keyword are skipped.

Results

The animation files Radioss writes (<run>A001, …) are read by radioss_anim (v16.11.0). The time history (T01) is not read; OpenRadioss's th_to_csv writes it as CSV.

Validation

/SURF/BOX, /SURF/PLANE, /SURF/ELLIPS and the other surface forms are skipped with a warning.

The fixtures under tests/python/meshes/radioss/ are written by tools/gen_radioss_fixtures.py from the card layouts of OpenRadioss's hm_cfg_files, plus two decks gmsh wrote, which read to the same cells as gmsh's own .msh of the same mesh; OpenRadioss's own QA decks are CC BY-NC and are not copied. Outside the repository the reader was run on the 81 starter decks of OpenRadioss's qa-tests/: every one reads, both engines agree, and every cell has a positive volume. For v16.11.0 the box, generator and surface semantics were taken from the OpenRadioss starter source (read, not copied) and the QA decks that use them (NEW_BOX_V11) resolve with both engines alike. No deck in the Radioss 4.x fixed formats (input versions 41 and 44) is publicly available, so those columns are still untested on real input.