Add the hyperelastic foam model also for JAX

src/felupe/constitution/jax/models/hyperelastic/__init__.py

@@ -1,17 +1,20 @@
 from ._miehe_goektepe_lulei import miehe_goektepe_lulei
 from ._mooney_rivlin import mooney_rivlin
+from ._storakers import storakers
 from ._third_order_deformation import third_order_deformation
 from ._yeoh import yeoh
 
 __all__ = [
     "miehe_goektepe_lulei",
     "mooney_rivlin",
+    "storakers",
     "third_order_deformation",
     "yeoh",
 ]
 
 # default (stable) material parameters
 miehe_goektepe_lulei.kwargs = dict(mu=0, N=100, U=0, p=2, q=2)
 mooney_rivlin.kwargs = dict(C10=0, C01=0)
+storakers.kwargs = dict(mu=[0], alpha=[2], beta=[1])
 third_order_deformation.kwargs = dict(C10=0, C01=0, C11=0, C20=0, C30=0)
 yeoh.kwargs = dict(C10=0, C20=0, C30=0)

src/felupe/constitution/jax/models/hyperelastic/_storakers.py

@@ -0,0 +1,34 @@
+# -*- coding: utf-8 -*-
+"""
+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/>.
+"""
+from functools import wraps
+from jax.numpy import array, sum as asum, sqrt
+from jax.numpy.linalg import eigvalsh
+
+from ....tensortrax.models.hyperelastic import storakers as storakers_docstring
+
+
+@wraps(storakers_docstring)
+def storakers(C, mu, alpha, beta):
+    λ1, λ2, λ3 = sqrt(eigvalsh(C))
+    J = λ1 * λ2 * λ3
+
+    μ = array(mu)
+    α = array(alpha)
+    β = array(beta)
+
+    return asum(2 * μ / α**2 * (λ1**α + λ2**α + λ3**α - 3 + (J ** (-α * β) - 1) / β))

src/felupe/constitution/tensortrax/models/hyperelastic/_storakers.py

@@ -21,12 +21,12 @@
 
 
 def storakers(C, mu, alpha, beta):
-    r"""Strain energy function of Storåkers' isotropic hyperelastic
-    `Foam <https://doi.org/10.1016/0022-5096(86)90033-5>`_ material formulation [1]_.
+    r"""Strain energy function of the Storåkers isotropic hyperelastic
+    `foam <https://doi.org/10.1016/0022-5096(86)90033-5>`_ material formulation [1]_.
 
     Parameters
     ----------
-    C : tensortrax.Tensor
+    C : tensortrax.Tensor or jax.Array
         Right Cauchy-Green deformation tensor.
     mu : list of float
         List of moduli.
@@ -66,11 +66,12 @@ def storakers(C, mu, alpha, beta):
 
     Examples
     --------
-    First, import the automatic differentiation backend
+    First, choose the desired automatic differentiation backend
 
     ..  pyvista-plot::
         :context:
 
+        >>> # import felupe.constitution.jax as mat
         >>> import felupe.constitution.tensortrax as mat
 
     and create the hyperelastic material [2]_.