Merge pull request #115 from adtzlr/simplify-microsphere-force

Simplify microsphere affine force

matadi/models/microsphere/affine/_models.py

@@ -40,26 +40,22 @@ def microsphere_affine_force(x, fun, *args, **kwargs):
 
     # extract current and initial deformation gradient and state variables
     F = x[0]
-    Fn = x[-2]
     statevars_n = x[-1]
 
     # volume ratios
     J = det(F)
-    Jn = det(Fn)
 
     # unimodular part of current and initial right Cauchy-Green deformation tensor
     C = F.T @ F
     CG = J ** (-2 / 3) * (C)
-    CGn = Jn ** (-2 / 3) * (Fn.T @ Fn)
 
     # affine stretches
-    lam_n = sqrt(diag(sphere.points.T @ CGn @ sphere.points))
     lam = sqrt(diag(sphere.points.T @ CG @ sphere.points))
 
     bulk = kwargs.pop("bulk")
 
     # fiber forces and state variable update
-    f, statevars = fun(lam, lam_n, statevars_n, *args, **kwargs)
+    f, statevars = fun(lam, statevars_n, *args, **kwargs)
 
     # Second Piola-Kirchhoff stress tensor
     SG = reshape(sum1(f / lam * sphere.weights * sphere.bases), 3, 3)

tests/test_microsphere.py

@@ -1,47 +1,43 @@
 import numpy as np
 
 from matadi import MaterialTensor, Variable
-from matadi.models.microsphere.affine import force
+from matadi.models.microsphere import affine
 
 
-def nh(stretch, stretch_n, statevars_n, mu=1.0):
+def nh(stretch, statevars_n, mu=1.0):
     "1d-Linear force-stretch consitututive material formulation."
 
     return 3 * mu * stretch, statevars_n
 
 
 def test_microsphere_force():
 
-    param = [nh, 1.0]
-
     F = Variable("F", 3, 3)
     Fn = Variable("Fn", 3, 3)
-    Zn = Variable("Zn", 2, 21)
+    Zn = Variable("Zn", 5, 21)
 
     umat = MaterialTensor(
-        x=[F, force.p, Fn, Zn],
-        fun=force,
-        args=param,
-        kwargs={"bulk": 5000},
-        statevars=2,
+        x=[F, affine.force.p, Zn],
+        fun=affine.force,
+        kwargs={"fun": nh, "mu": 1.0, "bulk": 5000},
+        statevars=1,
         triu=True,
     )
 
     F = np.random.rand(3, 3, 8, 100) / 2
-    Fn = np.random.rand(3, 3, 8, 100) / 2
     p = np.random.rand(1, 8, 100)
-    Zn = np.random.rand(2, 21, 8, 100)
+    Zn = np.random.rand(5, 21, 8, 100)
 
     for a in range(3):
         F[a, a] += 1
         Fn[a, a] += 1
 
-    P, Q, Z = umat.function([F, p, Fn, Zn])
-    A = umat.gradient([F, p, Fn, Zn])
+    P, Q, Z = umat.function([F, p, Zn])
+    A = umat.gradient([F, p, Zn])
 
     assert P.shape == (3, 3, 8, 100)
     assert Q.shape == (1, 1, 8, 100)
-    assert Z.shape == (2, 21, 8, 100)
+    assert Z.shape == (5, 21, 8, 100)
 
     assert len(A) == 3