Merge pull request #106 from adtzlr/improve-ogden

Improve Ogden & Enhance gradient stability of eigenvalues

matadi/__about__.py

@@ -1 +1 @@
-__version__ = "0.1.5"
+__version__ = "0.1.6"

matadi/math.py

@@ -11,6 +11,7 @@
     cross,
     times,
     eig_symbolic,
+    qr,
     ldl,
     # trig
     sin,
@@ -66,6 +67,8 @@
     Function,
 )
 
+import numpy as np
+
 eye = SX.eye
 ones = SX.ones
 zeros = SX.zeros
@@ -80,13 +83,16 @@ def invariants(T):
     return I1, I2, I3
 
 
-def eigvals(T, eps=1e-5):
-
-    T[0, 0] += eps
-    T[1, 1] -= eps
-
-    wT = eig_symbolic(T)
+def eigvals(T, eps=8e-5):
+
+    np.random.seed(136)
+
+    D = np.random.rand(3, 3) - 0.5
+    D = D.T @ D
+    D[1, 1] = -D[1, 1] 
+    D[2, 1] = D[1, 2] = -D[1, 2]
 
+    wT = eig_symbolic(T + D * eps)
     return wT
 
 

matadi/models/_hyperelasticity_isotropic.py

@@ -59,7 +59,7 @@ def ogden(F, mu, alpha):
     out = 0
     for m, a in zip(mu, alpha):
         wk = wC ** (a / 2)
-        out += m / a * (sum1(wk)[0, 0] - 3)
+        out += 2 * m / a ** 2 * (sum1(wk)[0, 0] - 3)
 
     return out
 

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "matadi"
-version = "0.1.5"
+version = "0.1.6"
 description = "Material Definition with Automatic Differentiation"
 readme = "README.md"
 requires-python = ">=3.6"
@@ -23,7 +23,7 @@ authors = [
 ]
 
 classifiers = [
-  "Development Status :: 3 - Alpha",
+  "Development Status :: 5 - Production/Stable",
   "Programming Language :: Python",
   "Intended Audience :: Science/Research",
   "License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)",

setup.cfg

@@ -1,6 +1,6 @@
 [metadata]
 name = matadi
-version = 0.1.5
+version = 0.1.6
 author = Andreas Dutzler
 author_email = a.dutzler@gmail.com
 description = Material Definition with Automatic Differentiation
@@ -13,7 +13,7 @@ long_description_content_type = text/markdown
 license = GPL-3.0-or-later
 license_file = LICENSE
 classifiers =
-    Development Status :: 3 - Alpha
+    Development Status :: 5 - Production/Stable
     Intended Audience :: Science/Research
     License :: OSI Approved :: GNU General Public License v3 or later (GPLv3+)
     Operating System :: OS Independent