ANYmaterial

Structural material models for finite-element analysis: isotropic and orthotropic elasticity, nonlinear hardening curves, and directional yield criteria, with a small tkinter editor and a command-line interface.

Install from PyPI with:

python -m pip install ANYmaterial

For work on the package itself, use the editable development setup below.

The distribution is ANYmaterial and the import package is anymaterial.

Quick start

import anymaterial as am

# Browse the library.
catalogue = am.library()
catalogue.names                      # 33 shipped materials
catalogue.find(category="aluminium")
catalogue.get("S355 (16 < t <= 40 mm)").build()

# Plot flow curves, with no plotting dependency.
am.write_curve_svg("curves.svg", [
    am.sample_curve(catalogue.get(name).spec.hardening_curve(), name)
    for name in ("S235 (t <= 16 mm)", "S355 (t <= 16 mm)", "S460 (t <= 16 mm)")
])

# Add your own, and it is there next time.
am.add_to_user_library(am.LibraryEntry(
    spec=am.MaterialSpec(
        name="Yard plate S355",
        constants={"elastic_modulus": 210e9, "poisson_ratio": 0.3},
        density=7850.0, yield_stress=362e6,
        hardening={"kind": "dnv_c208", "grade": "S355", "thickness": 0.02},
    ),
    category="structural steel",
    source="mill certificate 2026-07",
))

# A steel grade from the DNV-RP-C208 table, with its hardening curve.
plate = am.steel("S355", thickness=0.020, nonlinear=True)
plate.yield_stress          # 346.9e6 Pa, the 16 < t <= 40 row
plate.hardening_curve.flow_stress(0.05)

# What a shell formulation needs, derived from the compliance.
Q, transverse_shear, drilling = am.shell_material_matrices(plate)

# An orthotropic material with directional yield strengths.
ud = am.OrthotropicMaterial(
    "ud", 150e9, 10e9, 8e9, 0.25, 0.20, 0.30, 5e9, 4e9, 3e9,
    density=1600.0,
    hill_yield=am.Hill48Yield(400e6, 320e6, 280e6, 190e6, 175e6, 160e6),
)
am.beam_material_properties(ud).axial_modulus   # 150e9, not a fabricated E

Both are validated on construction, so an inadmissible combination of Poisson ratios raises where it is entered rather than producing a stiffness matrix that happens to be indefinite.

The library

33 materials ship with the package, and every one names where its numbers came from and what kind of number it is:

Three kinds of number, and only the first is a design value:

• tabulated — a standard's own table, reproduced with the reference.
• measured — the mean of a named test campaign. A mean is not a characteristic value: the measured mean yield of S355 is 412 MPa against a 357 MPa tabulated value, so using it as a design strength is unconservative. It is here to validate a nonlinear model against the tests it came from. Each entry carries its coupon count and coefficient of variation.
• indicative — a typical published figure for the grade. A grade designation covers a range that varies with product form, temper and thickness.

The distinction is carried through the API (LibraryEntry.is_design_value), the CLI (which prints the warning matching the statuses actually listed) and the editor, because a library that presents all three identically invites the wrong one to be used.

Attribution

The measured entries come from Hartloper, A. R., Ozden, S., de Castro e Sousa, A., & Lignos, D. G. (2022), Database of Uniaxial Cyclic and Tensile Coupon Tests for Structural Metallic Materials (v1.0.0), Zenodo, doi:10.5281/zenodo.6965147, licensed CC-BY-4.0. Each entry records the originating campaign citekey so the underlying experiments can be traced through the database's own reference list.

tabulated means the numbers are a standard's own table, reproduced with the reference. indicative means they are typical published figures and are not design values: a grade designation covers a range that varies with product form, temper and thickness, and the governing standard or the mill certificate is what settles it. The distinction is carried through the API, the CLI and the editor rather than being left in a README, because a library that presents a looked-up number and a qualified number identically invites the first to be used as the second.

A derived entry also records how it was derived, in LibraryEntry.calculation — the Ramberg-Osgood exponent behind a tabulated stainless curve, the transverse-isotropy assumption behind a lamina's G23. A derived number whose derivation is not recorded cannot be checked, and an assumption nobody can see is one nobody will question.

Every shipped entry must name a source, a standard and its notes — there is a test that fails the build if one does not. Entries whose cited source turned out not to support their numbers have been removed rather than kept with a caveat; see the changelog for which, and why.

The one composite is the IM7/8552 lamina, and it is careful about what it claims: E1, E2, G12 and nu12 are room-temperature-dry campaign means from the NCAMP qualification programme; E3, nu13, G13, nu23 and G23 are not measured and follow from an assumed transverse isotropy, with nu23 = 0.45 assumed outright. LibraryEntry.calculation says exactly which is which. It carries no yield stress and defines no failure criterion — composite failure is not isotropic yielding, and strengths belong in the B-basis allowables report, not here.

Materials you add go to ~/.anymaterial/materials.json, or wherever ANYMATERIAL_LIBRARY points — a project that wants its materials beside its models can say so. A user entry with the same name as a shipped one wins, which is how a grade gets corrected locally without editing the package.

Command line

anymaterial library --nonlinear

anymaterial plot "S235 (t <= 16 mm)" "S355 (t <= 16 mm)" -o curves.svg

anymaterial add "Yard plate" --elastic-modulus 210 --yield-stress 362 --grade S355 --thickness 0.02 --source "mill cert 2026-07"

library, plot, add, grades, properties, curve, show and validate, each with --json. validate exits non-zero when a material is inadmissible, so it works as a check in a build.

anymaterial-gui opens the library and editor: browse and filter the materials on the left, edit one in the middle, and on the right see the validation result, the derived shell and beam properties, the provenance of the selected library entry, and the flow curves — the material being edited plotted against whatever is selected, so a new material is seen against the grades it should sit near. Buttons load a library material into the form, add the current one to your library, and export the plotted curves to SVG.

Applications can use the same editor as a real picker. The optional callback adds a Use material button and receives a validated MaterialSpec:

from anymaterial.gui import open_material_editor

window, editor = open_material_editor(root, on_apply=material_dropdown.add)

This keeps material validation and unit conversion in ANYmaterial while the host decides how its dropdown or project model stores the selected material.

Scope

• Elastic symmetry — isotropic and orthotropic engineering materials, with a validated 6x6 compliance in Voigt order [11, 22, 33, 23, 13, 12].
• Reductions — the plane-stress, transverse-shear and beam-axis constants a shell or beam formulation needs, computed from compliance rather than from re-entered engineering constants.
• Nonlinear behaviour — flow curves as a function of equivalent plastic strain: bilinear, tabulated, power law, and the DNV-RP-C208 section 4.6.6 low-fractile steel curves.
• Directional yield — Hill-48 strengths in material axes, evaluated over a whole field of integration points at once.
• Serialization — a specification that survives a project-file round trip, recording how to rebuild its hardening curve rather than a frozen copy.
• A library — named materials in JSON, each carrying its category, its source and whether its numbers are a standard's table or a typical published figure, extensible at runtime.
• Plots — flow curves as standalone SVG, written by hand so that plotting costs no dependency.

Not in scope: section properties, meshes, elements, assembly or solution. General anisotropy, laminates and ply failure are out of scope, and are refused explicitly rather than approximated.

Design notes

Structural typing at the boundary. A consumer needs a name, a density, a declared elastic symmetry and an elastic_compliance_matrix(). Nothing has to inherit from anything here, which is what lets a material cross a package boundary — and why validation reads attributes rather than checking types.

Vectorization is part of the curve contract. flow_stress and hardening_modulus accept and return numpy arrays of any shape, because a return mapping calls them for every integration point and thickness layer at once.

Failing closed. Where the source material is silent this package raises rather than extrapolating: a plate thickness outside a tabulated RP-C208 range is an error, not an invitation to use the nearest row, and mean curves the recommended practice does not tabulate are unavailable rather than interpolated. An explicit thickness_class makes a documented deviation possible where an accident is not.

See docs/ARCHITECTURE.md for the layering, and MIGRATION.md for what was extracted from where.

Units

SI throughout. Stresses and moduli in Pa, densities in kg/m³, lengths in m, strains dimensionless. There is no conversion layer: a value that looks like MPa is a bug, not a convention. The RP-C208 tables are tabulated in MPa in the source document and converted once, at the data-file boundary. The editor accepts GPa and MPa because that is how they are quoted on a drawing, and converts at the widget.

Development

python -m pip install -e "C:\Github\ANYmaterial[dev]"
python -m pytest

To open the editor straight from a checkout — including an IDE's Run button, with nothing installed — run run_gui.py at the repository root. It puts src on sys.path first, so what runs is this working tree rather than an installed copy.

python run_gui.py