# Analytical reference (Peterson)

For a central hole in a finite-width strip under uniaxial tension, the stress concentration factor can be estimated with Peterson's polynomial (d/W ratio):

```
Kt ≈ 3.0 − 3.13·(d/W) + 3.66·(d/W)² − 1.53·(d/W)³
```

Nominal net-section stress: `σ_nom = σ_applied × W / (W − d)`

Peak von Mises (plane stress, uniaxial): `VM_max ≈ Kt × σ_nom`

Constants used on AIPhysics.org match `config/plate-with-hole-analytical.json` in the frontend repo
(W = 50 mm, σ_applied = 10 MPa).

Holdout **simulation** ground truth is in `doe/holdout_scalars.csv`; use analytical values as a sanity check only.
