Source code for felupe.constitution._user_materials_models

# -*- coding: utf-8 -*-
"""
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This file is part of felupe.

Felupe is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.

Felupe is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.

You should have received a copy of the GNU General Public License
along with Felupe.  If not, see <http://www.gnu.org/licenses/>.

"""

import numpy as np

from ..math import cdya_ik, ddot, dya, identity, sqrt, trace


[docs]def linear_elastic(, εn, σn, ζn, λ, μ, **kwargs): """3D linear-elastic material formulation. 1. Given state in point x (σn) (valid). 2. Given strain increment dε, so that ε = εn + dε. 3. Evaluation of the stress σ and the algorithmic consistent tangent modulus dσdε. dσdε = λ 1 ⊗ 1 + 2μ 1 ⊙ 1 σ = σn + dσdε : dε Arguments --------- dε : ndarray Strain increment. εn : ndarray Old strain tensor. σn : ndarray Old stress tensor. ζn : list List of old state variables. λ : float First Lamé-constant. μ : float Second Lamé-constant (shear modulus). """ # change of stress due to change of strain I = identity(dim=3, shape=(1, 1)) = 2 * μ * + λ * trace() * I # update stress σ = σn + # evaluate elasticity tensor if kwargs["tangent"]: dσdε = 2 * μ * cdya_ik(I, I) + λ * dya(I, I) else: dσdε = None # update state variables (not used here) ζ = ζn return dσdε, σ, ζ
[docs]def linear_elastic_plastic_isotropic_hardening(, εn, σn, ζn, λ, μ, σy, K, **kwargs): r"""Linear-elastic-plastic material formulation with linear isotropic hardening (return mapping algorithm). 1. Given state in point x (σn, ζn=[εpn, αn]) (valid). 2. Given strain increment dε, so that ε = εn + dε. 3. Evaluation of the hypothetic trial state: dσdε = λ 1 ⊗ 1 + 2μ 1 ⊙ 1 σ = σn + dσdε : dε s = dev(σ) εp = εpn α = αn f = ||s|| - sqrt(2/3) (σy + K α) 4. If f ≤ 0, then elastic step: Set y = yn + dy, y=(σ, ζ=[εp, α]), algorithmic consistent tangent modulus dσdε. Else: dγ = f / (2μ + 2/3 K) n = s / ||s|| σ = σ - 2μ dγ n εp = εpn + dγ n α = αn + sqrt(2 / 3) dγ Algorithmic consistent tangent modulus: dσdε = dσdε - 2μ / (1 + K / 3μ) n ⊗ n - 2μ dγ / ||s|| ((2μ 1 ⊙ 1 - 1/3 1 ⊗ 1) - 2μ n ⊗ n) Arguments --------- dε : ndarray Strain increment. εn : ndarray Old strain tensor. σn : ndarray Old stress tensor. ζn : list List of old state variables. λ : float First Lamé-constant. μ : float Second Lamé-constant (shear modulus). σy : float Initial yield stress. K : float Isotropic hardening modulus. """ I = identity() # elasticity tensor if kwargs["tangent"]: dσdε = λ * dya(I, I) + 2 * μ * cdya_ik(I, I) else: dσdε = None # elastic hypothetic (trial) stress and deviatoric stress = 2 * μ * + λ * trace() * I σ = σn + s = σ - 1 / 3 * trace(σ) * I # unpack old state variables α, εp = ζn # hypothetic (trial) yield function norm_s = sqrt(ddot(s, s)) f = norm_s - sqrt(2 / 3) * (σy + K * α) ζ = ζn # check yield function and create a mask where plasticity occurs mask = (f > 0)[0] # update stress, tangent and state due to plasticity if np.any(mask): = f / (2 * μ + 2 / 3 * K) n = s / norm_s εp = εp + * n α = α + sqrt(2 / 3) * # stress σ[..., mask] = (σ - 2 * μ * * n)[..., mask] # algorithmic consistent tangent modulus if kwargs["tangent"]: dσdε[..., mask] = ( dσdε - 2 * μ / (1 + K / (3 * μ)) * dya(n, n) - 2 * μ * / norm_s * (2 * μ * (cdya_ik(I, I) - 1 / 3 * dya(I, I)) - 2 * μ * dya(n, n)) )[..., mask] # update list of state variables ζ[0][..., mask] = α[..., mask] ζ[1][..., mask] = εp[..., mask] return dσdε, σ, ζ