import csv
from dataclasses import dataclass
from importlib.resources import files
from typing import Optional, Tuple
_FRICTIONAL_PRESET_FILE = "frictional_materials.csv"
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@dataclass
class IsotropicMaterial:
name: str
E: float # Young's Modulus (Pa)
nu: float # Poisson's Ratio
rho: float # Density (kg/m^3)
sigma_y: float = None # Yield Stress (Pa)
H: float = 0.0 # Hardening Modulus (Pa)
@property
def lame_params(self):
mu = self.E / (2 * (1 + self.nu))
lam = self.E * self.nu / ((1 + self.nu) * (1 - 2 * self.nu))
return mu, lam
Steel = IsotropicMaterial("Steel", E=210e9, nu=0.3, rho=7850, sigma_y=250e6)
Aluminum = IsotropicMaterial("Aluminum", E=70e9, nu=0.33, rho=2700, sigma_y=100e6, H=700e6) # Example H
Rubber = IsotropicMaterial("Rubber", E=10e6, nu=0.48, rho=1100)
Glass = IsotropicMaterial("Glass", E=70e9, nu=0.2, rho=2500)
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@dataclass(frozen=True)
class FrictionalMaterial:
"""Pressure-dependent (Drucker-Prager / Mohr-Coulomb) soil or rock material.
Holds the parameters consumed by the Drucker-Prager constitutive primitive
and the :class:`~tensormesh.assemble.DruckerPragerPlasticity` assembler.
Angles are in degrees.
The required fields are ``E``, ``nu``, ``cohesion`` and ``friction_angle``;
``dilatancy_angle``, ``H``, ``rho`` and ``name`` are optional, so a one-off
soil can be built directly::
soil = FrictionalMaterial(E=50e6, nu=0.30, cohesion=5e3, friction_angle=35.0)
A ``dilatancy_angle`` of ``None`` selects associated plastic flow (the
friction angle is used). Named presets are loaded from a small CSV table::
soil = FrictionalMaterial.from_preset("DenseSand")
Parameters
----------
E : float
Young's modulus in Pa.
nu : float
Poisson's ratio.
cohesion : float
Cohesion in Pa.
friction_angle : float
Mohr-Coulomb friction angle in degrees.
dilatancy_angle : float or None, optional
Dilatancy angle in degrees; ``None`` (default) means associated flow.
H : float, optional
Linear isotropic hardening modulus in Pa. Default ``0.0``.
rho : float or None, optional
Density in kg/m^3 (metadata; not used by the constitutive update).
name : str, optional
Label for the material. Default ``"Custom"``.
description : str, optional
Free-text note (set for presets).
"""
E: float
nu: float
cohesion: float
friction_angle: float
dilatancy_angle: Optional[float] = None
H: float = 0.0
rho: Optional[float] = None
name: str = "Custom"
description: str = ""
@property
def lame_params(self):
mu = self.E / (2 * (1 + self.nu))
lam = self.E * self.nu / ((1 + self.nu) * (1 - 2 * self.nu))
return mu, lam
@staticmethod
def _load_preset_table() -> dict:
text = files(__package__).joinpath(_FRICTIONAL_PRESET_FILE).read_text(encoding="utf-8")
table = {}
for row in csv.DictReader(text.splitlines()):
table[row["name"]] = row
return table
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@classmethod
def preset_names(cls) -> Tuple[str, ...]:
"""Return the names of the available frictional-material presets."""
return tuple(cls._load_preset_table().keys())
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@classmethod
def from_preset(cls, name: str) -> "FrictionalMaterial":
"""Build a :class:`FrictionalMaterial` from a named preset in the CSV table.
The preset values are *illustrative example presets*, not design-grade
soil/rock parameters.
Raises
------
KeyError
If ``name`` is not one of :meth:`preset_names`.
"""
table = cls._load_preset_table()
if name not in table:
available = ", ".join(sorted(table))
raise KeyError(
f"Unknown frictional-material preset {name!r}. Available presets: {available}."
)
row = table[name]
def _opt(value: str) -> Optional[float]:
value = value.strip()
return None if value == "" else float(value)
return cls(
E=float(row["E"]),
nu=float(row["nu"]),
cohesion=float(row["cohesion"]),
friction_angle=float(row["friction_angle"]),
dilatancy_angle=_opt(row.get("dilatancy_angle", "")),
H=float(row["H"]),
rho=_opt(row.get("rho", "")),
name=row["name"],
description=row.get("description", ""),
)