---
license: mit
size_categories: [10K<n<100K]
---
# OpenTO-NL

Finite-strain (geometrically nonlinear) topology optimization designs in the OpenTO scheme.

| column | type | meaning |
|---|---|---|
| `topology` | 1-bit image (nelx, nely) | the design, binary |
| `loads` | (n, 4) float32 | rows (c0, c1, fx, fy): node position in long-edge-normalized matrix coordinates and the PHYSICAL load vector |
| `boundary conditions` | (n, 4) float32 | rows (c0, c1, fix_x, fix_y) |
| `volume fraction` | float32 | target volume fraction |
| `aspect ratio` | float32 | nely / nelx |

Material: modified Saint Venant-Kirchhoff, plane strain, E = 1, nu = 0.3, unit elements, void at the SIMP
floor (E_min = 1e-6). Loads are absolute: the same structure at a larger load is a different, nonlinear problem.
Every design was checked with a finite-strain path-following solver and carries its applied load: a converged
equilibrium exists at the applied load and the design's limit load is at or above it.
Splits: `train` 84,667 samples, `test` 1,500 samples; the test boundary conditions (supports and load pattern)
do not occur in train at any volume fraction.